@article{ZucchiCorniaBoeseetal.1999, author = {Zucchi, Claudia and Cornia, Andrea and Boese, Roland and Kleinpeter, Erich and Alper, Howard and Palyi, Gyula}, title = {Preparation and molecular structures of benzyl- and phenyl-acetycobalt-carbonyls}, year = {1999}, language = {en} } @article{ZborowskiKochKleinpeteretal.2014, author = {Zborowski, Krzysztof Kazimierz and Koch, Andreas and Kleinpeter, Erich and Proniewicz, Leonard Marian}, title = {Searching for aromatic celate rings. Oxygen versus Thio and Seleno Ligands}, series = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics}, volume = {228}, journal = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics}, number = {8}, publisher = {De Gruyter}, address = {Berlin}, issn = {0942-9352}, doi = {10.1515/zpch-2014-0528}, pages = {869 -- 878}, year = {2014}, abstract = {As a part of searching for fully aromatic chelate compounds, copper complexes of malondialdehyde as well as its sulfur and selenium derivatives were investigated using the DFT quantum chemical methods. Chelate complexes of both Cu(I) and Cu(II) ions wereconsidered. Aromaticity of the metal complexes studied were analyzed using NICS(0), NICS(1), PDI, I-ring, MCI, ICMCI and I-B aromaticity indices, and by TSNMRS visualizations of the spatial magnetic properties. It seems that partial aromaticityof studied chelates increases when oxygen atoms in malondialdehyde are replaced by sulfur and selenium.}, language = {en} } @article{YonedaLealSeidletal.2007, author = {Yoneda, Julliane Diniz and Leal, Katia Zaccur and Seidl, Peter Rudolf and Azeredo, Rodrigo Bagueira de V. and Kleinpeter, Erich}, title = {Camphor : a good model for illustrating NMR techniques}, year = {2007}, abstract = {CAMPHOR: A GOOD MODEL FOR ILLUSTRATING NMR TECHNIQUES. The use of Nuclear Magnetic Resonance spectroscopy to establish the three-dimensional structures of molecules is an important component of modern Chemistry courses. The combination of techniques that can be used for this purpose is conveniently illustrated by their application to the camphor molecule. This paper presents applications of several techniques used in NMR spectral interpretation in an increasing order of complexity. The result of individual experiments is illustrated in order to familiarize the user with the way connectivity through bonds and through space is established from 1D/2D-NMR spectra and molecular stereochemistry is determined from different NMR experiments}, language = {en} } @article{WolfKleinpeter2005, author = {Wolf, G. and Kleinpeter, Erich}, title = {Pulsed field gradient NMR study of anomalous diffusion in a lecithin-based microemulsion}, issn = {0743-7463}, year = {2005}, abstract = {Self-diffusion measurements in microemulsion systems composed of a naturally occurring soybean lecithin mixture, an aqueous phase, either water or a 1\% aqueous PDADMAC solution, and isooctane were accomplished by pulsed field gradient (PFG) (HNMR)-H-1 spectroscopy at oil dilution lines of low and intermediate water/lecithin ratios. The concentration-dependent diffusion data reveal water-in-oil (W/O) reverse micellar aggregates with dimensions on the nanometer scale being slightly smaller at low water content. With increasing micellar volume fractions, both hydrodynamic as well as direct interactions between particles significantly slow aggregate diffusion. The surfactant mean square displacements (msd's) in dilute and concentrated polymer-free systems studied as a function of diffusion time (20-1000 ms) are characterized by a crossover from Gaussian diffusion, due to slow aggregate motion, to anomalously enhanced diffusion, due to fast surface-bulk surfactant exchange at intermediate times revealing weak, barrier-controlled adsorption behavior. Upon addition of the polycation PDADMAC, the diffusion characteristics change to exclusively superdiffusive behavior with surfactant msd scaling with time as t(3/2) over the entire time range studied. This is caused by surfactant molecules performing Levy walks along the surface of reverse micelles mediated by the dilute bulk. The bulk-mediated surface diffusion is a consequence of the diffusion-controlled micelle-bulk exchange dynamics induced by interactions of PDADMAC with surfactant headgroups}, language = {en} } @article{WentrupKochKleinpeter2016, author = {Wentrup, Curt and Koch, Rainer and Kleinpeter, Erich}, title = {Twisted C=C Double Bonds with Very Low Rotational Barriers in Dioxanediones and Isoxazolones Determined by Low-Temperature Dynamic NMR Spectroscopy and Computational Chemistry}, series = {European journal of organic chemistry}, journal = {European journal of organic chemistry}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-193X}, doi = {10.1002/ejoc.201600931}, pages = {4985 -- 4990}, year = {2016}, language = {en} } @article{WackerKleinpeter2007, author = {Wacker, Philipp and Kleinpeter, Erich}, title = {Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions}, doi = {10.1007/s10847-007-9332-1}, year = {2007}, abstract = {Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus csol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation.}, language = {en} } @article{WackerDahmsSengeetal.2007, author = {Wacker, Philipp and Dahms, Katja and Senge, Mathias O. and Kleinpeter, Erich}, title = {Conformational Landscape of meso-(1,3-Dithian-2-yl)porphyrins}, doi = {10.1021/Jo0708700}, year = {2007}, abstract = {An investigation of the conformational landscape of 1,3-dithian-2-yl bearing porphyrins and the rotational behavior of the dithianyl substituents in meso position was carried out by variable-temperature (VT) NMR spectroscopy. Additionally, theoretical results for alternative conformations and energy barriers were obtained by molecular modeling. The study revealed different NH trans tautomers with regard to the orientation of the dithianyl ligands for the free base porphyrins 1-3. Relatively ruffled porphyrin core conformations were established for the transition states of the dithianyl rotation, resulting in a lower rotational energy barrier for the nickel(II) complex 4 compared to that of the free base systems. The data obtained and the first depiction of a rotational transition state for the rotation of bulky meso-alkyl substituents illustrate the close structural interplay between meso-alkyl substituents and the macrocycle conformation in porphyrins.}, language = {en} } @article{VirtaKochRoslundetal.2005, author = {Virta, P. and Koch, Andreas and Roslund, M. U. and Mattjus, P. and Kleinpeter, Erich and Kronberg, L. and Sjoholm, R. and Klika, Karel D.}, title = {Synthesis, characterisation and theoretical calculations of 2,6-diaminopurine etheno derivatives}, issn = {1477-0520}, year = {2005}, abstract = {Four derivatives of 2,6-diaminopurine (1) were synthesised and characterised. When 1 was reacted with chloroacetaldehyde, 5-aminoimidazo[2,1- i] purine (2), 9-aminoimidazo[2,1-b]purine (3), 9-aminoimidazo[1,2- a]purine (4) and diimidazo[2,1-b: 2', 1'-i]purine (5) were formed. The purified products (3 - 5) were fully characterised by MS, complete NMR assignments as well as fluorescence and UV spectroscopy. The purified, isolated yields of these products ( 3 - 5) varied from 2.5 to 30\%. The relative stability of different tautomers was investigated by theoretical calculations. Fluorescence characteristics are also discussed and compared to the starting material 1 and a reference molecule 2-aminopurine}, language = {en} } @article{ThothSzatmariHeydenreichetal.2009, author = {Th{\´o}th, Di{\´a}na and Szatm{\´a}ri, Istv{\´a}n and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Fulop, Ferenc}, title = {Synthesis and conformational analysis of naphthylnaphthoxazine derivatives}, issn = {0166-1280}, doi = {10.1016/j.molstruc.2009.04.015}, year = {2009}, abstract = {Four new primary aminonaphthols (4, 5, 9 and 10) were synthesized from 1- or 2-naphthol and 1- or 2- naphthaldehyde via naphthoxazines in modified Mannich condensations. Simple ring-closure reactions of these aminonaphthols with paraformaldehyde, 4-nitrobenzaldehyde, phosgene or 4-chlorophenyl isothiocyanate led to new heterocyclic derivatives. In these transformations, either an sp2 or an sp3 carbon was inserted between the hydroxy and amino groups. The effects of substituents and the naphthyl ring on the conformation were investigated by means of NMR measurements, employing both dipolar and scalar couplings. The structures were confirmed by DFT quantum chemical calculations involving computed coupling constants, intramolecular distances between nuclei and the relative energies of the preferred conformers.}, language = {en} } @article{ThomasKleinpeter2005, author = {Thomas, Steffen and Kleinpeter, Erich}, title = {A novel empirical approach for the structure elucidation of disilanes by empirical estimation of their Si-29 chemical shifts}, issn = {0022-2860}, year = {2005}, abstract = {In C-13 NMR spectroscopy, there are many empirical methods for fast and exact computation of C-13 chemical shifts; comparable procedures for Si-29 NMR chemical shifts are not existing or are older than 20 years. On basis of the largest database of Si-29 chemical shifts available, along this paper a relatively simple procedure for the similarly exact calculation of the Si-29 chemical shifts of disilanes (average margin of error ca. 3.7 ppm) is given. (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{ThomasKleinpeter1996, author = {Thomas, Steffen and Kleinpeter, Erich}, title = {Internet und World Wide Web : Nutzen f{\"u}r den NMR Spektroskopiker}, year = {1996}, language = {de} } @article{ThomasKleinpeter1995, author = {Thomas, Steffen and Kleinpeter, Erich}, title = {Zur Zuordnung der 13C-Chemischen Verschiebungen substituierter Naphthaline aus Ladungsdichten mit Hilfe eines neuronalen Netzes}, year = {1995}, language = {de} } @article{ThomasBruehlHeilmannetal.1997, author = {Thomas, Steffen and Br{\"u}hl, Iris and Heilmann, Dieter and Kleinpeter, Erich}, title = {13 C NMR Chemical shift calculations for some substituted pyridines - a comparative consideration}, year = {1997}, language = {en} } @article{ThieleRottmannGermeretal.2002, author = {Thiele, Gabriela and Rottmann, Antje and Germer, Antje and Kleinpeter, Erich and Spindler, Klaus-Dieter and Synstad, Bjoenar and Eijsink, Vincent G. H. and Peter, Martin G.}, title = {Synthesis and conformational analysis of pseudosugar analogues of chitotriose}, year = {2002}, abstract = {In this article, the synthesis of analogs of N,N',N''-triacetylchitotriose in which the central sugar residue was replaced by a succinic acid is presented. Mol. modeling calcns. revealed that the pseudotrisaccharides exist in low energy extended conformations which show similar space filling as N,N',N''-triacetylchitotriose. Of the N,N',N''-triacetylchitotriose pseudosugar analogs tested as chitinase inhibitors, none showed any appreciable competition (numerical data not presented). The conformational anal. along with further synthetic efforts will hopefully lead to more efficient pseudosaccharides as chitinase inhibitors.}, language = {en} } @article{TaddeiKleinpeter2005, author = {Taddei, F. and Kleinpeter, Erich}, title = {The anomeric effect in substituted cyclohexanes : II. The role of hyperconjugative interactions and steric effect in 1,4-disubstituted cyclohexanes}, issn = {0166-1280}, year = {2005}, abstract = {The conformational equilibria of the cis/trans isomers of some 1,4-di-substituted cyclohexanes (X = OH, OMe, Me, OCOCH3, OCOC(CH3)(3), OCOCCl3, OCOCF3) were calculated at several levels of theory; the best correlation between calculated and experimentally available Delta G(0)s refers to the MP2/6-311 +G*//MP2/6-311G* results. In addition, the hyperconjugative effect of the substituents was studied with the NBO options included in the GAUSSIAN-98 package; a number of interactions between filled NBOs and antibonding orbitals could be considered as most representative for delocalization along the molecules studied. The effect of the substituents on the molecular geometry of the substituted cyclohexanesas well as the partitioning of both hyperconjugative and steric substituent effects on the present conformational equilibria is critically evaluated. Our model [E. Kleinpeter, F. Taddei, J. Mol. Struct. (THEOCHEM) 683 (2004) 29] for interpreting the relative stability of conformers of substituted cyclohexanes could be further verified and its reliability assessed. (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{TaddeiKleinpeter2004, author = {Taddei, F. and Kleinpeter, Erich}, title = {The anomeric effect in substituted cyclohexanes : I. The role of hyperconjugative interactions and steric effect in monosubstituted cyclohexanes}, issn = {0166-1280}, year = {2004}, abstract = {The relative energy of conformers, DeltaE, of monosubstituted cyclohexanes with OR (R = Me, Et, i-Pr and t-Bu) and R substituents (R = Me, Et, i-Pr and t-Bu) was calculated with MO ab initio theory at RHF, MP2 and QCISD levels with the 6-311G* and 6-311 + G* basis sets. A selected group of delocalizing interactions were calculated with the natural bond orbital method in order to quantify the hyperconjugative contribution, DeltaE(hyp.), to the relative stability of conformers. From the calculated values of DeltaE and DeltaE(hyp.) an estimate of the differential steric effect, DeltaE(ster.), of substituents in cyclohexane was obtained. The values of DeltaE(hyp), and DeltaE(ster.) show that they have a similar magnitude for OR substituents, while for R substituents the values of are greater. The shift in the conformational equilibrium towards the axial conformer, the so-called anomeric effect, takes place when, within a series of substituents, hyperconjugative interactions and steric interactions balance in favour of the stability of this conformer. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{SzatmariTothKochetal.2006, author = {Szatmari, Istvan and Toth, Diana and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc}, title = {Study of the substituent-influenced anomeric effect in the ring-chain tautomerism of 1-alkyl-3-aryl-naphth[1,2- e][1,3]oxazines}, doi = {10.1002/ejoc.200600563}, year = {2006}, abstract = {The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values.}, language = {en} } @article{SzatmariMartinekLazaretal.2004, author = {Szatmari, Istvan and Martinek, T. A. and Lazar, L. and Koch, Andreas and Kleinpeter, Erich and Neuvonen, Kari and Fulop, Ferenc}, title = {Stereoelectronic effects in ring-chain tautomerism of 1,3-diarylnaphth[1,2-e][1,3]oxazines and 3-alkyl-1- arylnaphth[1,2-e][1,3]oxazines}, issn = {0022-3263}, year = {2004}, abstract = {The disubstitution effects of X and Y in 1-(Y-phenyl)-3-(X-phenyl)-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines on the ring-chain tautomerism, the delocalization of the nitrogen lone pair (anomeric effect), and the C-13 NMR chemical shifts were analyzed by using multiple linear regression analysis. Study of the three-component equilibrium B reversible arrow A reversible arrow C revealed that the chain reversible arrow trans (A reversible arrow B) equilibrium constants are significantly influenced by the inductive effect (sigma(F)) of substituent Y on the 1-phenyl ring. In contrast, no significant substituent dependence on Y was observed for the chain reversible arrow cis (A reversible arrow C) equilibrium. There was an analogous dependence for the epimerization (C reversible arrow B) constants of 1-(Y-phenyl)-3- alkyl-2,3-dihydro-1H-naphth[1,2-e] [1,3]oxazines. With these model compounds, significant overlapping energies of the nitrogen lone pair was observed by NBO analysis in the trans forms B (to sigma*(C1-C1'), sigma*(C1-C10b), and sigma*(C3-O4)) and in the cis forms C (to sigma*(C1-H), sigma*(C1-C10b), and sigma*(C3-O4)). The effects of disubstitution revealed some characteristic differences between the cis and trans isomers. However, the results do not suggest that the anomeric effect predominates in the preponderance of the trans over the cis isomer. When the C-13 chemical shift changes induced Y by substituents X and Y (SCS) were subjected to multiple linear regression analysis, negative rho(F)(Y) and rho(F)(X) values were observed at C-1 and C-3 for both the cis and trans isomers. In contrast, the positive rho(R)(Y) values at C-1 and the negative rho(R)(X) values at C-3 observed indicated the contribution of resonance structures f (rho(R) > 0) and g (rho(R) < 0), respectively. The classical double bond-no-bond resonance structures proved useful in explaining the substituent sensitivities of the donation energies and the behavior of the SCS values}, language = {en} } @article{SzatmariHeydenreichKochetal.2013, author = {Szatmari, Istvan and Heydenreich, Matthias and Koch, Andreas and Fulop, Ferenc and Kleinpeter, Erich}, title = {Unexpected isomerization of new naphth[1,3]oxazino[2,3-a] isoquinolines in solution, studied by dynamic NMR and supported by theoretical DFT computations}, series = {Tetrahedron}, volume = {69}, journal = {Tetrahedron}, number = {35}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2013.06.094}, pages = {7455 -- 7465}, year = {2013}, abstract = {Through the reactions of 1-aminomethyl-2-naphthol and substituted 1-aminobenzyl-2-naphthols with 3,4-dihydroisoquinoline or 6,7-dimethoxy-3,4-dihydroisoquinoline under microwave conditions, naphth[1,2-e][1,3]oxazino[2,3-a]-isoquinoline derivatives were prepared in good yields. The latter reaction was extended by using 2-aminoarylmethyl-1-naphthols, leading to isomeric naphth-[2,1-e][1,3]oxazino[2,3-a] isoquinolines. Beside the detailed NMR spectroscopic and theoretical study of both stereochemistry and dynamic behaviour of these new conformational flexible heterocyclic ring systems an unexpected dynamic process between two diastereomers was observed in solution, studied by variable temperature H-1 NMR spectroscopy and the mechanism proved by theoretical DFT computations.}, language = {en} } @article{SzatmariBelasriHeydenreichetal.2019, author = {Szatmari, Istvan and Belasri, Khadija and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Fulop, Ferenc}, title = {Ortho-Quinone methide driven synthesis of new O,N- or N,N-Heterocycles}, series = {ChemistryOpen : including thesis treasury}, volume = {8}, journal = {ChemistryOpen : including thesis treasury}, number = {7}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2191-1363}, doi = {10.1002/open.201900150}, pages = {961 -- 971}, year = {2019}, abstract = {To synthesize functionalized Mannich bases that can serve two different types of ortho-quinone methide (o-QM) intermediates, 2-naphthol and 6-hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o-QM and aza-o-QM were also synthesized by mixing 2-naphthol, 2-nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio- and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o-QMs/aza-o-QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H-benzo[a]xanthen-12-one (11), formed via o-QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low-field position of proton H-1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)-C(1)-C(12b)-C(12a)-C(12)=O structural fragment.}, language = {en} } @article{StroehlThomasRadegliaetal.1992, author = {Str{\"o}hl, D. and Thomas, Steffen and Radeglia, R. and Brunn, J. and Kleinpeter, Erich}, title = {13C-NMR-Untersuchungen von Substituenteneffekten in mehrfach substituierten Benz-und Naphthalenderivaten ; Inkrementberechnungen der 13C-chemischen Verschiebungen}, year = {1992}, language = {de} } @article{StroehlKleinpeter1993, author = {Str{\"o}hl, D. and Kleinpeter, Erich}, title = {Zur Stereochemie acyclischer Verbindungen : III. Bestimmung der Vorzugskonformstion unterschiedlich substituirternY-Chlorpropylether}, year = {1993}, language = {de} } @article{StojanovicMarkovicKleinpeteretal.2011, author = {Stojanovic, Milovan and Markovic, Rade and Kleinpeter, Erich and Baranac-Stojanovic, Marija}, title = {endo-Mode cyclizations of vinylogous N-acyliminium ions as a route to the synthesis of condensed thiazolidines}, issn = {0040-4020}, year = {2011}, language = {en} } @article{StojanovicMarkovicKleinpeteretal.2011, author = {Stojanovic, Milovan and Markovic, Rade and Kleinpeter, Erich and Baranac-Stojanovic, Marija}, title = {Endo-Mode cyclizations of vinylogous N-acyliminium ions as a route to the synthesis of condensed thiazolidines}, series = {Tetrahedron}, volume = {67}, journal = {Tetrahedron}, number = {49}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2011.10.011}, pages = {9541 -- 9554}, year = {2011}, abstract = {endo-Mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined as a route to the synthesis of condensed thiazolidines. The scope of these reactions and stereochemical outcome are discussed and explained using quantum chemical calculations.}, language = {en} } @article{StojanovicMarkovicKleinpeteretal.2012, author = {Stojanovic, Milovan and Markovic, Rade and Kleinpeter, Erich and Baranac-Stojanovic, Marija}, title = {Synthesis of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions}, series = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, volume = {10}, journal = {Organic \& biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry}, number = {3}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1477-0520}, doi = {10.1039/c1ob06451g}, pages = {575 -- 589}, year = {2012}, abstract = {Syntheses of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined and discussed. The formation of (5,6)-membered systems was feasible with all nucleophiles tried (O, S and N), while the closing of the five-membered ring was restricted to O- and S-nucleophiles. The closure of a four-membered ring failed. Instead, the bicyclic (5,6)-membered acetal derivative and the tricyclic system with an eight-membered central ring were obtained from the substrates containing O and S nucleophilic moieties, respectively. The reaction outcome and stereochemistry are rationalized using quantum chemical calculations at B3LYP/6-31G(d) level. The exclusive cis-stereoselectivity in the formation of (5,6)- and (5,5)-membered systems results from thermodynamic control, whereas the formation of the eight-membered ring was kinetically controlled.}, language = {en} } @article{StarkeSchusterFulopetal.2008, author = {Starke, Ines and Schuster, Ildikk{\´o} and Fulop, Ferenc and Kleinpeter, Erich}, title = {Mass spectra of tetrahydroisoquinoline-fused 1,3,2-O,N,P- and 1,2,3-O,S,N-heterocycles: influence of ring size and fusion, of present heteroatoms, substituent effects and of the stereochemistry on fra}, year = {2008}, abstract = {The electron ionization (EI) mass spectra of a variety of stereoisomeric tricyclic 1,3,2-oxazaphosphino[4,3- a]isoquinolines (1-4), 1,2,3-oxathiazino[4,3-a]isoquinoline-4-oxides (5-7) and the -4,4-dioxides (8-10) of oxazaphospholo- and oxathiazolo[4,3-a]- (11, 12, 15 and 16) and -[3,4-b]isoquinolines (13, 14 and 17) were recorded. Ring size and fusion, the different heteroatoms (P and S) and substituents on the ring systems strongly influence the mass spectra. In addition, mass spectra of the stereoisomers of compounds 1, 2 and 13, 14 revealed stereochemically relevant differences which are not observed for the other pairs of isomers. Copyright © 2008 John Wiley \& Sons, Ltd.}, language = {en} } @article{StarkeKochUhlemannetal.1995, author = {Starke, Ines and Koch, Andreas and Uhlemann, Erhard and Kleinpeter, Erich}, title = {Nuclear-magnetic-resonance studies and molecular modelling of the solution structure of some dibenzo crown- ethers and their complexes}, year = {1995}, language = {en} } @article{StarkeKochHoldtetal.1995, author = {Starke, Ines and Koch, Andreas and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich}, title = {1H, 13C, and 15N NMR study of the solution structure of metabridged bis(benzo-15-crown-5-ether)s}, year = {1995}, language = {en} } @article{StarkeKammerHoldtetal.2010, author = {Starke, Ines and Kammer, Stefan and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich}, title = {Stability of disubstituted copper complexes in the gas phase analyzed by electrospray ionization mass spectrometry}, issn = {0951-4198}, doi = {10.1002/Rcm.4519}, year = {2010}, abstract = {A series of nitrogen ligand (L)/copper complexes of the type [(CuL)-L-I](+), [(CuL)-L-II(X)](+) and [(CuL2)-L- I](+) (X = Cl-, BF4-, acac(-), CH3COO- and SO3CF3-) was studied in the gas phase by electrospray ionization mass spectrometry. The following ligands (L) were employed: 1,12-diazaperylene (dap), 1,1'-bisiso-quinoline (bis), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,11-disubstituted 1,12-diazaperylenes (dap), 3,3'- disubstituted 1,1'-bisisoquinoline (bis), 5,8-dimethoxy-substituted diazaperylene (meodap), 6,6'-dimethoxy- substituted bisisoquinoline (meobis) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Collision-induced decomposition measurements were applied to evaluate the relative stabilities of the different copper complexes. The influence of the spatial arrangement of the ligands, of the type of substituents and of the counter ion of the copper salts employed for the complexation was examined. Correlations were found between the binding constants of the [ML2](+) complexes in solution and the relative stabilities of the analogous complexes in the gas phase. Furthermore, complexation with the ligands 2,11-dialkylated 1,12-diazaperylenes [alkyl = ethyl (dedap) and isopropyl (dipdap)] was studied in the solvents CH3OH and CH3CN.}, language = {en} } @article{StarkeKammerGrunwaldetal.2008, author = {Starke, Ines and Kammer, Stefan and Grunwald, Nicolas and Schilde, Uwe and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich}, title = {Complexation of diazaperylene and bisisoquinoline with transition metal ions in the gas phase studied by electrospray ionization mass spectrometry}, year = {2008}, abstract = {The complex formation of the ligands 1,12-diazaperylene (dap), 1,1-bisisoquinoline (bis), 2,2-bipyridine (bpy) and 1,10-phenanthroline (phen) with transition metal ions (M = Fe, Co, Ni, Cu, Zn, Ru, Os, Re, Pd, Pt, Ag and Cd) in the gas phase has been studied by electrospray ionization mass spectrometry. With the exception of Ru, Os, Fe, Ni and Cu, singly charged complexes [MLn]+ (n = 1,2) were observed. The complexes of dap and bis with Ru, Os, Fe and Ni ions, and the mixed ligand complexes with bpy and phen, are preferably of the doubly charged type [ML3]2+. In addition, collision- induced dissociation (CID) measurements were employed to evaluate the relative stabilities of these complexes. The CID experiments of mixed-ligand complexes which contain both dap and phen or dap and bpy exhibit preferential elimination of bpy, indicating that bpy is a weaker ligand than phen and dap.}, language = {en} } @article{StarkeHolzbergerKammetal.2000, author = {Starke, Ines and Holzberger, Anja and Kamm, Birgit and Kleinpeter, Erich}, title = {Qualitative and quantitative analysis of carbohydrates in green juices (wild mix grass and alfalfa) from a green biorefinery by gas chromatography/mass spectrometry}, year = {2000}, language = {en} } @article{StarkeFuerstenbergMuelleretal.2006, author = {Starke, Ines and F{\"u}rstenberg, Sylvia and M{\"u}ller, Holger and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich}, title = {Electrospray mass spectrometric studies of the complexational behavior of maleonitrile thiacrown ethers with various metals}, doi = {10.1002/Rcm.2384}, year = {2006}, abstract = {Electrospray ionization was employed to study the mass spectrometric behavior of the maleonitrile tetrathiacrown ethers mn12S(4) (1) and mn13S(4) (2) and maleonitrile pentathiacrown ether mn15S(5) (3) and of their complexes with various metal salts (MX2, M=Pd, Pt, Ni, Co, Fe; X=Cl, CrCl3, Ni(BF4)(2), TIPF6 or Cd(NO3)(2)) and Cu(SO3CF3)(2). Both singly charged, [MXL](+) and [MXL2]+, and doubly charged complexes, [MLn](2+) (n = 2-5), were observed. The formation of the different complexes consisting of the transition metal ion, the counterion and the various crown ethers and their subsequent dissociation was also studied by collision-induced dissociation measurements which were also used to evaluate the relative stabilities of the complexes. It was found that the collisional voltages for the dissociation of the complexes were generally greater in the [MXL](+) complexes than in the corresponding [MXL2]+ complexes. Copyright (c) 2006 John Wiley \& Sons, Ltd}, language = {en} } @article{StarkeSarodnickOvcharenkoetal.2004, author = {Starke, I. and Sarodnick, Gerhard and Ovcharenko, V. V. and Pihlaja, Kalevi and Kleinpeter, Erich}, title = {Quinoxalines : Part 13: Synthesis and mass spectrometric study of aryloxymethylquinoxalines and benzo[b]furylquinoxalines}, issn = {0040-4020}, year = {2004}, abstract = {A series of new aryloxymethylquinoxalines, benzo[b]- and naphtho[2,1-b] fury] quinoxalines, possessing potential biological activity, was prepared, characterized by IR and NMR spectroscopy and their electron ionization (EI) mass spectra studied in detail. The aryloxymethylquinoxalines were obtained by reacting halogenomethylquinoxalines with bifunctional O-nucleophiles. The benzo[b]furylquinoxalines and naphtho[2, I -b]furylquinoxalines were prepared via two routes, which differed in the order of the two cyclization steps involved in the syntheses. The composition of the ions obtained by El mass spectrometry were determined by accurate mass measurements and the fragmentation pathways clarified by B/E linked scans and collision induced dissociation. The mass spectrometric behaviour of the compounds studied as to the possible loss of OH' radicals proved to be very characteristic. (C) 2004 Elsevier Ltd. All rights reserved}, language = {en} } @article{ShainyanUshakovTolstikovaetal.2008, author = {Shainyan, Bagrat A. and Ushakov, Igor A. and Tolstikova, Ljudmila L. and Koch, Andreas and Kleinpeter, Erich}, title = {N-Trifyl substituted 1,4-diheterocyclohexanes{\`u}stereodynamics and the Perlin effect}, year = {2008}, abstract = {The stereodynamic behaviour of 1-(trifluoromethylsulfonyl)piperidine 1, 4-(trifluoromethylsulfonyl)morpholine 2, 1,4-bis(trifluoromethylsulfonyl)piperazine 3 and 4-(trifluoromethylsulfonyl)thiomorpholine 1,1-dioxide 4 was studied by low-temperature 1H, 13C and 19F NMR spectroscopies. In acetone solution, compounds 1, 2 and 4 were found to exist as mixtures of two conformers in the ratio of 4:1, 4:1 and 8:1, respectively, differing by orientation of the CF3 group with respect to the ring. Compound 3 exists as a mixture of three conformers in the ratio of 3:28:69 also differing by the orientation of the two CF3 groups. Unlike the previously studied N-trifyl substituted 1,3,5-triheterocyclohexanes, the preferred conformers of compound 1 and of 1,4-diheterocyclohexanes 2-4 are those with the CF3 group directed outward from the ring, which is caused by intramolecular interactions of the oxygen atoms of the CF3SO2N groups with the equatorial hydrogens in the ;-position. B3LYP/6-311+G(d,p) calculations of the energy, geometry and NMR parameters corroborate the experimental data. The calculated Perlin effects for all conformers of compounds 1-4 as well as those measured for the major conformers of compounds 3 and 4 were analyzed by the use of the NBO analysis.}, language = {en} } @article{ShainyanUshakovMeshcheryakovetal.2007, author = {Shainyan, Bagrat A. and Ushakov, Igor A. and Meshcheryakov, Vladimir I. and Schilde, Uwe and Koch, Andreas and Kleinpeter, Erich}, title = {The stereodynamics of 3,5-bis(trifluoromethylsulfonyl)-1,3,5-oxadiazinane and 1,3,5- tris(trifluoromethylsulfonyl)-1,3,5-triazinane- an experimental and theoretical study}, doi = {10.1016/j.tet.2007.09.041}, year = {2007}, abstract = {Multinuclear dynamic NMR spectroscopy of 3,5-bis(trifluoromethylsulfonyl)-1,3,5-oxadiazinane (3) revealed the existence of two conformers with differently oriented CF3 groups with respect to the ring, and two dynamic processes: ring inversion and restricted rotation about the N-S bond. Two transition states connecting the two conformers and corresponding to clockwise and counterclockwise rotations about the N-S bond were found; the calculated activation barriers of about 12 kcal/mol are in excellent agreement with those measured experimentally for the related molecule 1,3,5-tris(trifluoromethylsulfonyl)-1,3,5-triazinane (1). X-ray analysis proved the existence of the symmetric isomer of 3, which is the minor isomer in solutions but the only one in the crystal due to packing effects. The normal Perlin effect (JCHax < JCHeq)observed for 2(6)-CH2 in 3, whereas the reversed Perlin effect was found for the 4-CH2 group in 3 as well as for all CH2 groups in 1 both experimentally and theoretically. The latter effect in compounds 1, 3, and 1- (methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane (2) can be considered as a genuine reverse Perlin effect since larger values of 1JCH are observed for longer C-H bonds.}, language = {en} } @article{ShainyanUshakovMeshcheryakovetal.2008, author = {Shainyan, Bagrat A. and Ushakov, Igor A. and Meshcheryakov, Vladimir I. and Koch, Andreas and Kleinpeter, Erich}, title = {Variable temperature NMR and theoretical study of the stereodynamics of 5-trifluoromethylsulfonyl-1,3,5- dioxaazinane : Perlin effect subject to heteroatom substitution}, year = {2008}, abstract = {Multinuclear dynamic NMR spectroscopy of 5-trifluoromethylsulfonyl-1,3,5-dioxaazinane (4) revealed the existence of two close in energy chair conformers with differently oriented CF3 groups with respect to the ring. Of the two alternative routes for their interconversion, the ring inversion path with intermediate formation of the corresponding 2,5-twist-conformer is preferred, with the energy barrier of 11.2 kcal/mol in excellent agreement with the experimental value (11.7 kcal/mol). The Perlin effect is studied experimentally and calculated theoretically for all CH2 groups and found to be subject to the nature of the adjacent heteroatoms O and N, respectively.}, language = {en} } @article{ShainyanUshakovKochetal.2006, author = {Shainyan, Bagrat A. and Ushakov, Igor A. and Koch, Andreas and Kleinpeter, Erich}, title = {Stereodynamics of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane: Experimental and theoretical analysis}, doi = {10.1021/Jo061112x}, year = {2006}, abstract = {Dynamic NMR of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane reveals the existence of three conformers and two dynamic processes: ring inversion and rotation about the N-S bond, both processes having Delta G(double dagger) = 13.5 kcal/mol. An unprecedented large reverse Perlin effect (J(CHax) > J(CHeq)) was found experimentally and calculated theoretically.}, language = {en} } @article{ShainyanSuslovaTranDinhPhienetal.2018, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Tran Dinh Phien, and Shlykov, Sergey A. and Kleinpeter, Erich}, title = {Synthesis, conformational preferences in gas and solution, and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations}, series = {Tetrahedron}, volume = {74}, journal = {Tetrahedron}, number = {32}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2018.06.023}, pages = {4299 -- 4307}, year = {2018}, abstract = {1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature C-13 NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph-ax conformer (1-Ph-eq:1-Ph-ax ratio of 20:80\%, Delta G degrees (317 K) = -0.87 kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C-ipso and C(1,5) carbon signals in C-13 NMR spectra at 103 K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2 = 1:1:3), which is still liquid at 100 K, the 1-Ph-eq conformer was found to be the preferred one [(1-Ph-eq: 1-Ph-ax = 77\%: 23\%, K = 77/23 = 2.8; -Delta G degrees = -RT In K (at 103 K) = 0.44 +/- 0.1 kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X = H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph-ax conformer in the gas phase and of the Ph-eq conformer in solution is confirmed.}, language = {en} } @article{ShainyanSuslovaTranDinhPhienetal.2019, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Tran Dinh Phien, and Shlykov, Sergey A. and Heydenreich, Matthias and Kleinpeter, Erich}, title = {1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations}, series = {Tetrahedron}, volume = {75}, journal = {Tetrahedron}, number = {46}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2019.130677}, pages = {9}, year = {2019}, abstract = {1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature C-13 and Si-29 NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeSaxPheq conformer in gas phase (1-Ph-eq :1-Ph-ax = 55:45, Delta G degrees = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph-eq:1-Ph-ax = 65:35, Delta G degrees = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory. (C) 2019 Elsevier Ltd. All rights reserved.}, language = {en} } @article{ShainyanSuslovaKleinpeter2012, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Kleinpeter, Erich}, title = {Conformational analysis of 4,4-dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane and 2,2,6,6-tetramethyl-4- (trifluoromethylsulfonyl)-1,4,2,6-oxazadisilinane}, year = {2012}, abstract = {4,4-Dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane 1 and 2,2,6,6-tetramethyl-4-(trifluoromethylsulfonyl)- 1,4,2,6-oxazadisilinane 2 were studied by variable temperature dynamic 1H, 13C, 19F NMR spectroscopy and theoretical calculations at the DFT (density functional theory) and MP2 (Moller-Plesset 2) levels of theory. Both kinetic (barriers to ring inversion) and thermodynamic data (frozen conformational equilibria) could be obtained for the two compounds. The computations revealed two minima on the potential energy surface for molecules 1 and 2 corresponding to the rotamers with the CF3SO2 group directed inward and outward the ring, the latter being 0.20.4 kcal/mol (for 1) and 1.1 kcal/mol (for 2) more stable than the former. The vibrational calculations at the DFT and MP2 levels of theory give the values of the free energy difference Delta G degrees for the 'inward' reversible arrow 'outward' equilibrium consistent with those determined from the experimentally measured ratio of the rotamers. The structure of crystalline compound 2 was ascertained by X-ray diffraction analysis.}, language = {en} } @article{ShainyanSuslovaKleinpeter2011, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Kleinpeter, Erich}, title = {Conformational analysis of N-phenyl- and N-trifyl-4,4-dimethyl-4-silathiane 1-sulfimides}, series = {Journal of physical organic chemistry}, volume = {24}, journal = {Journal of physical organic chemistry}, number = {8}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0894-3230}, doi = {10.1002/poc.1811}, pages = {698 -- 704}, year = {2011}, abstract = {N-Substituted 4,4-dimethyl-4-silathiane 1-sulfimides Me2Si(sic)S=NSO2R [R- Ph (1), CF3 (2)] were studied experimentally by variable temperature dynamic NMR spectroscopy. Low temperature 13 C NMR spectra of the two compounds revealed the frozen ring inversion process and approximately equal content of the axial and equatorial conformers. Calculations of the 4-silathiane derivatives 1, 2 and the model compound [R Me (3)] as well as their carbon analogs, the similarly N-substituted (sic)S=NSO2R thiane 1-sulfimides [R = Ph (4), CF3 (5), Me (6)] at the DFT/B3LYP/6-311G(d, p) level in the gas phase and in chloroform solution using the PCM model at the same level of theory showed a strong dependence of the relative stability of the conformer on the solvent. The electronegative trifluoromethyl group increases the relative stability of the axial conformer.}, language = {en} } @article{ShainyanSuslovaKleinpeter2012, author = {Shainyan, Bagrat A. and Suslova, Elena N. and Kleinpeter, Erich}, title = {Conformational analysis of 4,4-dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane and 2,2,6,6-tetramethyl-4-(trifluoromethylsulfonyl)-1,4,2,6-oxazadisilinane}, series = {Journal of physical organic chemistry}, volume = {25}, journal = {Journal of physical organic chemistry}, number = {1}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0894-3230}, doi = {10.1002/poc.1882}, pages = {83 -- 90}, year = {2012}, abstract = {4,4-Dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane 1 and 2,2,6,6-tetramethyl-4-(trifluoromethylsulfonyl)-1,4,2,6-oxazadisilinane 2 were studied by variable temperature dynamic 1H, 13C, 19F NMR spectroscopy and theoretical calculations at the DFT (density functional theory) and MP2 (Moller-Plesset 2) levels of theory. Both kinetic (barriers to ring inversion) and thermodynamic data (frozen conformational equilibria) could be obtained for the two compounds. The computations revealed two minima on the potential energy surface for molecules 1 and 2 corresponding to the rotamers with the CF3SO2 group directed inward and outward the ring, the latter being 0.20.4 kcal/mol (for 1) and 1.1 kcal/mol (for 2) more stable than the former. The vibrational calculations at the DFT and MP2 levels of theory give the values of the free energy difference Delta G degrees for the 'inward' reversible arrow 'outward' equilibrium consistent with those determined from the experimentally measured ratio of the rotamers. The structure of crystalline compound 2 was ascertained by X-ray diffraction analysis.}, language = {en} } @article{ShainyanMoskalikHeydenreichetal.2014, author = {Shainyan, Bagrat A. and Moskalik, Mikhail Yu and Heydenreich, Matthias and Kleinpeter, Erich}, title = {Conformational equilibrium and dynamic behavior of bis-N-triflyl substituted 3,8-diazabicyclo[3.2.1]octane}, series = {Magnetic resonance in chemistry}, volume = {52}, journal = {Magnetic resonance in chemistry}, number = {8}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0749-1581}, doi = {10.1002/mrc.4086}, pages = {448 -- 452}, year = {2014}, abstract = {Restricted rotation about the N-S partial double bonds in a bis-N-triflyl substituted 3,8-diazabicyclo[3.2.1]octane derivative 1 has been frozen at low temperature (Delta G* = 11.6 kcal mol(-1)), and the existence of all four rotamers about the two N-S bonds, 3-in, 8-in, 3-in, 8-out, 3-out, 8-in, and 3-out, 8-out, respectively, proved experimentally by NMR spectroscopy and theoretically by DFT and MP2 calculations. Copyright (C) 2014 John Wiley \& Sons, Ltd.}, language = {en} } @article{ShainyanKleinpeter2012, author = {Shainyan, Bagrat A. and Kleinpeter, Erich}, title = {Conformational preferences of Si-Ph,H and Si-Ph,Me silacyclohexanes and 1,3-thiasilacyclohexanes : Additivity of conformational energies in 1,1-disubstituted heterocyclohexanes}, issn = {0040-4020}, year = {2012}, abstract = {The conformational equilibria of 1-phenyl-1-silacyclohexane 1, 3-phenyl-1,3-thiasilacyclohexane 2, 1-methyl-1- phenyl-1-silacyclohexane 3, and 3-methyl-3-phenyl-1,3-thiasilacyclohexane 4 have been studied for the first time by low temperature C-13 NMR spectroscopy at 103 K. Predominance of the equatorial conformer of compound 1 (Ph-eq/Ph-ax=78\%:22\%) is much less than in its carbon analog, phenylcyclohexane (nearly 100\% of Ph-eq). And in contrast to 1-methyl-1- phenylcyclohexane, the conformers with the equatorial Ph group are predominant for compounds 3 and 4: at 103 K, Ph-eq/Ph- ax ratios are 63\%:37\% (3) and 68\%:32\% (4). As the Si-C bonds are elongated with respect to C-C bonds, the barriers to ring inversion are only between 5.2-6.0 (ax -> eq) and 5.4-6.0 (eq -> ax) kcal mol(-1). Parallel calculations at the DFT and MP2 level of theory (as well as the G2 calculations for compound 1) show qualitative agreement with the experiment. The additivity/nonadditivity of conformational energies of substituents on cyclohexane and silacyclohexane derivatives is analyzed. The geminally disubstituted cyclohexanes containing a phenyl group show large deviations from additivity, whereas in 1-methyl-1-phenyl-1-silacyclohexane and 3-methyl-3-phenyl-1,3-thiasilacyclohexane the effects of the methyl and phenyl groups are almost additive. The reasons for the different conformational preferences in carbocyclic and heterocyclic compounds are analyzed using the homodesmotic reactions approach.}, language = {en} } @article{ShainyanKleinpeter2013, author = {Shainyan, Bagrat A. and Kleinpeter, Erich}, title = {Silacyclohexanes and silaheterocyclohexanes-why are they so different from other heterocyclohexanes?}, series = {Tetrahedron}, volume = {69}, journal = {Tetrahedron}, number = {29}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2013.04.126}, pages = {5927 -- 5936}, year = {2013}, abstract = {Stereochemical studies on silaheterocyclohexanes is a 'hot topic' as evidenced by the growing number of publications. During last 10 years a substantial number of substituted silacyclohexanes and heterocyclohexanes containing sulfur, oxygen or nitrogen as the second (or third) heteroatom have been synthesized and studied by variable temperature dynamic NMR spectroscopy, gas-phase electron diffraction, variable temperature IR, Raman, microwave spectroscopy with respect to thermodynamic (frozen conformational equilibria) and kinetic (barrier to ring inversion) information. As the stereochemistry of cyclohexane and its N-, O-, P-, S-hetero analogues is one of keystones of modern theoretical and synthetic organic and heterocyclic chemistry, the stereochemistry of silacyclohexane and its hetero analogs is an important element of theoretical and synthetic organosilicon chemistry. The various classes of saturated six-membered rings were critically compared and studied in detail with respect to differences in their stereochemistry and dynamic behavior.}, language = {en} } @article{ShainyanKleinpeter2014, author = {Shainyan, Bagrat A. and Kleinpeter, Erich}, title = {Conformational flexibility of 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline and its monoheterocyclic analogs}, series = {Russian journal of general chemistry}, volume = {84}, journal = {Russian journal of general chemistry}, number = {7}, publisher = {Pleiades Publ.}, address = {New York}, issn = {1070-3632}, doi = {10.1134/S1070363214070135}, pages = {1325 -- 1329}, year = {2014}, abstract = {Conformational behavior of the first cyclic organosilicon vinylsulfide, 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline as well as its monoheterocyclic analogs, 3,4-dihydro-2H-pyran, 3,4-dihydro-2H-thiopyran, and 1,1-dimethyl-1,2,3,4-tetrahydrosiline is studied in comparison with the carbocyclic analog, cyclohexene, using the methods of low-temperature NMR spectroscopy and theoretical calculations at the DFT and MP2 levels of theory. The barrier to the ring inversion with respect to that in cycloxene is increased in 3,4-dihydro-2H-pyran and 1,1-dimethyl-1,2,3,4-tetrahydrosiline, but, in contrast to the suggestions made in the literature, is decreased in 3,4-dihydro-2H-thiopyran. In 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline the barrier is intermediate between those in the corresponding monoheterocycles, 1,1-dimethyl-1,2,3,4-tetrahydrosiline and 3,4-dihydro-2H-thiopyran. The observed variations are rationalized from the viewpoint of the interaction of the pi-electrons of the C=C double bond with the orbitals of heteroatoms in the ring. The structure of the transition state for the ring inversion is discussed.}, language = {en} } @article{ShainyanKleinpeter2012, author = {Shainyan, Bagrat A. and Kleinpeter, Erich}, title = {Conformational preferences of Si-Ph,H and Si-Ph,Me silacyclohexanes and 1,3-thiasilacyclohexanes. Additivity of conformational energies in 1,1-disubstituted heterocyclohexanes}, series = {Tetrahedron}, volume = {68}, journal = {Tetrahedron}, number = {1}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2011.10.082}, pages = {114 -- 125}, year = {2012}, abstract = {The conformational equilibria of 1-phenyl-1-silacyclohexane 1, 3-phenyl-1,3-thiasilacyclohexane 2, 1-methyl-1-phenyl-1-silacyclohexane 3, and 3-methyl-3-phenyl-1,3-thiasilacyclohexane 4 have been studied for the first time by low temperature C-13 NMR spectroscopy at 103 K. Predominance of the equatorial conformer of compound 1 (Ph-eq/Ph-ax=78\%:22\%) is much less than in its carbon analog, phenylcyclohexane (nearly 100\% of Ph-eq). And in contrast to 1-methyl-1-phenylcyclohexane, the conformers with the equatorial Ph group are predominant for compounds 3 and 4: at 103 K, Ph-eq/Ph-ax ratios are 63\%:37\% (3) and 68\%:32\% (4). As the Si-C bonds are elongated with respect to C-C bonds, the barriers to ring inversion are only between 5.2-6.0 (ax -> eq) and 5.4-6.0 (eq -> ax) kcal mol(-1). Parallel calculations at the DFT and MP2 level of theory (as well as the G2 calculations for compound 1) show qualitative agreement with the experiment. The additivity/nonadditivity of conformational energies of substituents on cyclohexane and silacyclohexane derivatives is analyzed. The geminally disubstituted cyclohexanes containing a phenyl group show large deviations from additivity, whereas in 1-methyl-1-phenyl-1-silacyclohexane and 3-methyl-3-phenyl-1,3-thiasilacyclohexane the effects of the methyl and phenyl groups are almost additive. The reasons for the different conformational preferences in carbocyclic and heterocyclic compounds are analyzed using the homodesmotic reactions approach.}, language = {en} } @article{ShainyanKirpichenkoKleinpeteretal.2015, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich and Shlykov, Sergey A. and Osadchiy, Dmitriy Yu.}, title = {Molecular structure and conformational analysis of 3-methyl-3-phenyl-3-silatetrahydropyran. Gas-phase electron diffraction, low temperature NMR and quantum chemical calculations}, series = {Tetrahedron}, volume = {71}, journal = {Tetrahedron}, number = {23}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2015.03.117}, pages = {3810 -- 3818}, year = {2015}, abstract = {The molecular structure and conformational behavior of 3-methyl-3-phenyl-3-silatetrahydropyran 1 was studied by gas-phase electron diffraction (GED-MS), low temperature C-13 NMR spectroscopy (LT NMR) and theoretical calculations. The 1-Ph-eq and 1-Ph-ax conformers were located on the potential energy surface. Rotation about the Si-C-ph bond revealed the phenyl ring orthogonal to the averaged plane of the silatetrahydropyran ring for 1-Ph-eq and a twisted orientation for 1-Ph-ax. Theoretical calculations and GED analysis indicate the predominance of 1-Ph-ax in the gas phase with the ratio of conformers (GED) 1-Ph-eq:1-Ph-ax=38:62 (Delta G degrees(307)=-0.29 kcal/mol). In solution, LT NMR spectroscopy gives almost the opposite ratio Ph-eq:1-Ph-ax=68:32 (Delta G degrees(103)=0.16 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of compound 1 in the gas phase and in solution. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @article{ShainyanKirpichenkoKleinpeteretal.2013, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich and Shlykov, Sergey A. and Osadchiy, Dmitriy Yu and Chipanina, Nina N. and Oznobikhina, Larisa P.}, title = {1,3-Dimethy1-3-silapiperidine - synthesis, molecular structure, and conformational analysis by gas-phase electron diffraction, low temperature NMR, IR and Raman Spectroscopy, and quantum chemical calculations}, series = {The journal of organic chemistry}, volume = {78}, journal = {The journal of organic chemistry}, number = {8}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/jo400289g}, pages = {3939 -- 3947}, year = {2013}, abstract = {The first Si-H-containing azasilaheterocycle, 1,3-dimethyl-3-silapiperidine 1, was synthesized, and its molecular structure and conformational properties were studied by gas-phase electron diffraction (GED), low temperature NMR, IR and Raman spectroscopy and quantum chemical calculations. The compound exists as a mixture of two conformers possessing the chair conformation with the equatorial NMe group and differing by axial or equatorial position of the SiMe group. In the gas phase, the SiMeax conformer predominates (GED: ax/eq = 65(7):35(7)\%,Delta G = 0.36(18) kcal/mol; IR: ax/eq = 62(5):38(5)\%,Delta G = 0.16(7) kcal/mol). In solution, at 143 k the SiMeeq conformer predominates' in the frozen equilibrium (NMR: ax/eq = 31.5(1.5):68.5(1.5)\%, Delta G = -0.22(2) kcal/mol). Thermodynamic parameters of the ring inversion are determined (Delta G(double dagger) = 8.9-9.0 kcal/mol, Delta H-double dagger = 9.6 kcal/mol, Delta S-double dagger = 2.1 eu). High-level quantum chemical calculations :(MP2, G2, CCSD(T)) nicely reproduce the experimental geometry and the predominance of the axial conformer in the gas phase.}, language = {en} } @article{ShainyanKirpichenkoKleinpeter2012, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich}, title = {Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane low temperature dynamic NMR and computational study}, series = {Arkivoc : free online journal of organic chemistry}, journal = {Arkivoc : free online journal of organic chemistry}, number = {24}, publisher = {ARKAT}, address = {Gainesville}, issn = {1551-7004}, pages = {175 -- 185}, year = {2012}, abstract = {1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the PhaxMeeq and PheqMeax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined.}, language = {en} }