@article{ShainyanKirpichenkoKleinpeter2012, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich}, title = {Synthesis and conformational analysis of 1,3-azasilinanes}, series = {Tetrahedron}, volume = {68}, journal = {Tetrahedron}, number = {36}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2012.05.106}, pages = {7494 -- 7501}, year = {2012}, abstract = {1-Isopropyl-3-methyl-3-phenyl-1,3-azasilinane 1 and 1-isopropyl-3,3-dimethyl-1,3-azasilinane 2 were synthesized and a detailed analysis of their NMR spectra, conformational equilibria and ring inversion processes is presented. Low temperature H-1/C-13 NMR spectroscopy, iteration of the H-1 NMR spectra and quantum chemical calculations showed slight predominance of the PheqMeax over the PhaxMeeq conformer of 1 at low temperature. The barrier for the chair to chair interconversion of both compounds was measured to be 8.25 kcal/mol.}, 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} } @article{ShainyanKirpichenkoKleinpeter2017, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich}, title = {Conformational Preferences of the Phenyl Group in 1-Phenyl-1-X-1-silacyclo-hexanes (X = MeO, HO) and 3-Phenyl-3-X-3-silatetrahydropyrans (X = HO, H) by Low Temperature C-13 NMR Spectroscopy and Theoretical Calculations}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.7b02505}, pages = {13414 -- 13422}, year = {2017}, abstract = {New Si-phenyl-substituted silacyclohexanes and 3-silatetrahydropyrans have been synthesized and studied with respect to the conformational equilibria of the heterosix-membered ring by low temperature C-13 NMR spectroscopy and quantum chemical calculations. For 1-methoxy-1-phenylsilacyclohexane 1 and 3-phenyl-3-silatetrahydropyran 4 the conformational equilibria could be frozen and assigned. The Ph-ax reversible arrow Ph-eq equilibrium constants at 103 K are 2.21 for 1 and 4.59 for 4. In complete agreement with former studies of similar silicon compounds, molecules 1 and 4 prefer to adopt the Pheq conformation. The conformational equilibria of 1-hydroxy-1-phenylsilacydohexane 2 and 3-hydroxy-3-phenyl-3-silatetrahydropyran 3 could not be frozen at 100 K and proved to be heavily one-sided (if not anancomeric). Obviously, there is a general trend of predominance of Phax conformer in the gas phase and of Pheq in solution. For the isolated molecules of silanols 2 and 3, calculations allowed to explain the axial predominance of the phenyl group by a larger polarization of the Si-Ph than of the Si-O bond in the Phax conformer and additional destabilization of 3-Ph-eq conformer by repulsion of unidirectional dipoles of the endocyclic oxygen lone pair and of the highly polar axial Si-O bond.}, language = {en} } @article{ShainyanKirpichenkoChipaninaetal.2015, author = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Chipanina, Nina N. and Oznobikhina, Larisa P. and Kleinpeter, Erich and Shlykov, Sergey A. and Osadchiy, Dmitriy Yu.}, title = {Synthesis and Conformational Analysis of 3-Methyl-3-silatetrahydropyran by GED, FTIR, NMR, and Theoretical Calculations: Comparative Analysis of 1-Hetero-3-methyl-3-silacyclohexanes}, series = {The journal of organic chemistry}, volume = {80}, journal = {The journal of organic chemistry}, number = {24}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.5b02355}, pages = {12492 -- 12500}, year = {2015}, abstract = {3-Methyl-3-silatetrahydropyran 1 was synthesized and its molecular structure and conformational behavior was studied by gas-phase electron diffraction (GED), FTIR, low temperature H-1 and C-13 NMR spectroscopy, and by theoretical calculations (DFT, MP2). Two conformers; 1-ax and 1-eq; were located on the potential energy Surface. In the gas phase; a slight predominance of the axial conformer was determined, with the ratio 1-ax:1-eq = 54(9):46(9) (from GED) or 53:47 or 61;39 (from IR). In solution, LT NMR spectroscopy at 103 K gives the ratio 1-ax:1-eq = 35:65 (-Delta G(103)degrees = 0.13 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the corresponding solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of 3-methyl-3-silatettahydropyran in the gas phase and in solution. Comparative analysis of the effect of heteroatom in 1-hetero-3-methyl-3-silacyclohexanes on the structure, stereoelectronic interactions, and relative energies of the conformers is done.}, language = {en} } @article{ShainyanFettkeKleinpeter2008, author = {Shainyan, Bagrat A. and Fettke, Anja and Kleinpeter, Erich}, title = {Push-pull vs captodative aromaticity}, issn = {1089-5639}, doi = {10.1021/jp804999m}, year = {2008}, abstract = {Vinylogs of fulvalenes with cyclopropenyl and cyclopentadienyl moieties attached either to different carbon atoms (c-C3H2-CH-CH=C5H4-c, 7) or to the same carbon atom [X=C(c-C3H2)(c-C5H4), 10] [X = CH2; C(CN)2; C(NH2)2; C(OCH2)2; O; c-C3H2; c-C5H4; SiH2; CCl2] of the double bond inserted between the two rings are examined theoretically at the B3LYP/ 6;311G(d,p) level. Both types of compounds are shown to possess aromaticity, which was called "push;pull" and "captodative" aromaticity, respectively. For the captodative mesoionic structures X=C(c-C3H2)(c-C5H4), the presence of both the two aromatic moieties and the C=C double bond is the necessary and sufficient condition for their existence as energetic minima on the potential energy surface. Aromatic stabilization energy (ASE) was assessed by the use of homodesmotic reactions and heats of hydrogenation. Spatial magnetic criteria (through space NMR shieldings, TSNMRS) of the two types of vinylogous fulvalenes 7 and 10 have been calculated by the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Ragu{\´e}; Schleyer, and visualized as iso-chemical-shielding surfaces (ICSS) of various sizes and directions. TSNMRS values can be successfully employed to visualize and quantify the partial push;pull and captodative aromaticity of both the three- and five-membered ring moieties. In addition, the push;pull effect in compounds 7 and 10 could be quantified by the occupation quotient ;*C=C/;C=C of the double bond inserted between the two rings.}, language = {en} } @article{ShainyanBelyakovSigolaevetal.2017, author = {Shainyan, Bagrat A. and Belyakov, Alexander V. and Sigolaev, Yurii F. and Khramov, Alexander N. and Kleinpeter, Erich}, title = {Molecular Structure and Conformational Analysis of 1-Phenyl-1-X-1-Silacyclohexanes (X = F, Cl) by Electron Diffraction, Low-Temperature NMR, and Quantum Chemical Calculations}, series = {The journal of organic chemistry}, volume = {82}, journal = {The journal of organic chemistry}, number = {1}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.6b02538}, pages = {461 -- 470}, year = {2017}, abstract = {The molecular structure and conformational preferences of 1-phenyl-1-X-1-silacyclohexanes C5H10Si(Ph,X) (X = F (3), Cl (4)) were studied by gas-phase electron diffraction, low-temperature NMR spectroscopy, and high-level quantum chemical calculations. In the gas phase only three (3) and two (4) stable conformers differing in the axial or equatorial location of the phenyl group and the angle of rotation about the Si-C-ph bond (axi and axo denote the Ph group lying in or out of the X-Si-C-ph plane) contribute to the equilibrium. In 3 the ratio Ph-eq:Ph-axo:Ph-axi is 40(12):55(24):5 and 64:20:16 by experiment and theory, respectively. In 4 the ratio Ph-eq:Ph-axo is 79(15):21(15) and 71:29 by experiment and theory (M06-2X calculations), respectively. The gas-phase electron diffraction parameters are in good agreement with those obtained from theory at the M06-2X/aug-ccPVTZ and MP2/aug-cc-pVTZ levels. Unlike the case for M06-2X, MP2 calculations indicate that 3-Ph-eq conformer lies 0.5 kcal/mol higher than the 3-Ph-axo, conformer. As follows from QTAIM analysis, the phenyl group is more stable when it is located in the axial position but produces destabilization of the silacyclohexane ring: By low temperature NMR spectroscopy the six-membered ring interconversion could be frozen, at 103 K and the present conformational equilibria of 3 and 4 could be determined. The ratio of the conformers is 3-Ph-eq:3-Ph-ax = (75-77):(23-25) and 4-Ph-eq:4-Ph-ax = 82:18.}, language = {en} } @article{ShainyanKleinpeterSuslova2019, author = {Shainyan, Bagrat A. and Kleinpeter, Erich and Suslova, E. N.}, title = {Conformational Analysis of (1,1′-Phenyl-1,1′-silacyclohex-1-yl)disiloxane}, series = {Russian journal of general chemistry}, volume = {89}, journal = {Russian journal of general chemistry}, number = {4}, publisher = {Pleiades Publ.}, address = {New York}, issn = {1070-3632}, doi = {10.1134/S1070363219040121}, pages = {713 -- 716}, year = {2019}, abstract = {The DFT and MP2 theoretical conformational analysis of the recently synthesized (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane has revealed the energetic preference of the Ph-ax,Ph-ax conformer. The Ph-ax,Ph-ax: Ph-ax,Ph-eq: Ph-eq,Ph-eq conformers ratio has been estimated as of 46.6: 33.1: 20.3 from the M062X/6-311G(d,p) free energy simulation, suggesting the possibility of detecting individual conformers experimentally, e.g., by low-temperature H-1 and C-13 NMR spectroscopy. However, only the presence of several conformers has been detected by means of H-1 NMR spectroscopy at 113 K; determination of the (Hz) and G(\#) (kcal/mol) parameters for the 6-membered ring interconversion has been impossible due to the signals broadening at low temperature, signal temperature shifts, and extremely low barrier of ring inversion at T-c < 113 K.}, language = {en} } @article{SeidlCarneiroTostesetal.2005, author = {Seidl, Peter Rudolf and Carneiro, J. W. D. and Tostes, J. G. R. and Koch, Andreas and Kleinpeter, Erich}, title = {Interpretation of conformational effects on 2-endo-norborneol by natural chemical shielding analysis}, issn = {1089-5639}, year = {2005}, abstract = {This paper represents an extension of our work on the H-1 and C-13 NMR chemical shifts of norbornane and 2-endo- norborneol. NCS-NBO analysis was employed to probe contributions of bond orbitals and orbitals of lone pairs to nuclear shielding in conformers of the alcohol generated by rotation of the C-O bond. Variations in H-1 and C-13 chemical shifts with the dihedral angle are discussed in terms of Lewis and non-Lewis partitioning and their respective importance is evaluated. In addition to hyperconjugation of the lone pair in a p orbital of oxygen that was previously reported, a sizable participation of the lone pair which is in an sp orbital is also observed and their combined effect dominates the carbon chemical shifts of the C-1-C-2-OH and C-3-C-2-OH fragments. Both lone pairs on oxygen also contribute to localized, though-space effects on nuclei in the vicinity, these effects answering for the largest deviations in hydrogen chemical shifts on rotation around the C-O bond. On the other hand, for conformers in which nonbonded repulsions lead to distortions in the molecular framework, variations in chemical shifts may be attributed to angular effects}, language = {en} } @article{SchusterKochHeydenreichetal.2008, author = {Schuster, Ildik{\´o} and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Forr{\´o}, Enik{\"o} and L{\´a}z{\´a}r, L{\´a}szl{\´o} and Sillanp{\"a}{\"a}, Reijo and Fulop, Ferenc}, title = {Synthesis and Conformational Analysis of Tetrahydroisoquinoline-Fused 1,3,2-Oxazaphospholidines and 1,2,3- Oxathiazolidines}, year = {2008}, abstract = {The cyclizations of tetrahydroisoquinoline 1,2-amino alcohols with phenylphosphonic dichloride, bis(2- chloroethyl)phosphoramidic dichloride, thionyl chloride and sulfuryl chloride were utilized to synthesize 1,5,6,10b- tetrahydro-1,3,2-oxazaphospholo[4,3-a]isoquinolines (2, 3), 1,5,10,10a-tetrahydro-1,3,2-oxazaphospholo[3,4- b]isoquinolines (8, 9), 1,5,6,10b-tetrahydro-1,2,3-oxathiazolo[4,3-a]isoquinolines (4-6) anda 1,5,10,10a-tetrahydro- 1,2,3-oxathiazolo[3,4-b]isoquinoline (11), which are the first representatives of these ring systems. NMR spectroscopic analysis revealed the existence of conformational equilibria that are fast on the NMR timescale. Theoretical DFT calculations pointed to the participation of generally two preferred conformers in the conformational equilibria; the positions of the equilibria were indicated by the experimental NMR spectroscopic parameters, and they are in good agreement with the theoretically calculated energy differences of the participating conformers. For two compounds, which could be not isolated (10, 12), both the preferred conformers and the stereochemistry could be concluded from the DFT calculation results.}, language = {en} } @article{SchollKochHenningetal.1999, author = {Scholl, S. and Koch, Andreas and Henning, Dietrich and Kempter, Gerhard and Kleinpeter, Erich}, title = {The influence of structure and lipophilicity of hydantoin derivatives on anticonvulsant activity}, year = {1999}, language = {en} } @article{SchildeErkKleinpeter2006, author = {Schilde, Uwe and Erk, {\c{C}}akil and Kleinpeter, Erich}, title = {The crystal and molecular structures of sodium and barium complexes of dibenzo-24-crown-8 ether}, doi = {10.1524/zkri.2006.221.3.231}, year = {2006}, abstract = {The sodium and barium isothiocyanate complexes of 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]- 1,4,7,10,13,16,19,22-octaoxacyclotetracosin (dibenzo-24-crown-8 ether = DB24C8) were synthesized and analyzed by X-ray diffraction. The sodium complex, [Na(DB24C8)(NCS)(H2O)] 1, crystallizes in the orthorhombic space group Fdd2 with 16 molecules in the unit cell. The coordination number of Na is 6 and the central ion is located in a distorted octahedric environment. Only four of the crown ether oxygen atoms are involved. The coordination polyhedron is completed by the isothiocanate anion and by a water molecule, which is stabilized by hydrogen bonds. The barium complex, [Ba(DB24C8)(NCS)(2)] 2, crystallizes in the trigonale space group P3(1)21 with 3 molecules in the unit cell. Crystallographic C-2 symmetry is observed for the complex. The coordination number of Ba is 10. Barium is coordinated with the eight oxygen atoms of the macrocyclic ligand and with two isothiocyanate anions. The absolute structure was estimated using the FLACK parameter}, language = {en} } @article{ScheerTroitzschHilfertetal.1995, author = {Scheer, M. and Troitzsch, Ch. and Hilfert, Liane and Dargatz, M. and Kleinpeter, Erich and Jones, P. G. and Sieler, J.}, title = {PX-Liganden mit maximaler Elektronendonorf{\"a}higkeit, 7 : die Dreikomponenenreaktion von P4-Phosphor}, year = {1995}, language = {de} } @article{SarodnickLinkerHeydenreichetal.2009, author = {Sarodnick, Gerhard and Linker, Torsten and Heydenreich, Matthias and Koch, Andreas and Starke, Ines and F{\"u}rstenberg, Sylvia and Kleinpeter, Erich}, title = {Quinoxalines XV : convenient synthesis and structural study of pyrazolo[1,5-alpha]quinoxalines}, issn = {0022-3263}, doi = {10.1021/Jo802398g}, year = {2009}, abstract = {A series of aryloxymethylquinoxaline oximes, hitherto unknown and synthesized from the corresponding aldehydes, afforded in only one step pyrazolo[1,5-;]quinoxalines in the presence of acetic anhydride at high temperatures. A formal [3,5]-sigmatropic rearrangement was proposed as the mechanistic rationale for this unprecedented transformation. Saponification with potassium hydroxide furnished the free phenol derivatives which were studied by NMR spectroscopy and accompanying theoretical DFT calculations, establishing intramolecular hydrogen bonding and the spatial magnetic properties. Additionally, mass spectrometric fragmentation was investigated by B/E-linked scans and collision-induced dissociation experiments. The fragmentation pattern devoted a new gas phase rearrangement process, which proved to be unique and characteristic for pyrazolo[1,5-;]quinoxalines.}, language = {en} } @article{SarodnickHilfertKempteretal.1997, author = {Sarodnick, Gerhard and Hilfert, Liane and Kempter, Gerhard and Kleinpeter, Erich}, title = {Reactin of 2-(halogenomethyl)-quinoxalines and quinolines with hydroxybenzoic acids and their esters}, year = {1997}, language = {en} } @article{SarodnickHeydenreichLinkeretal.2003, author = {Sarodnick, Gerhard and Heydenreich, Matthias and Linker, Torsten and Kleinpeter, Erich}, title = {Quinoxalines : Part 12: Synthesis and structural study of 1-(thiazol-2-yl)-1H-pyrazolo[3,4-b]quinoxalines - the dehydrogenative cyclization with hydroxylamine hydrochloride}, year = {2003}, language = {en} } @article{SardarianInalooModarresiAlametal.2019, author = {Sardarian, Ali Reza and Inaloo, Iman Dindarloo and Modarresi-Alam, Ali Reza and Kleinpeter, Erich and Schilde, Uwe}, title = {Metal-Free Regioselective Monocyanation of Hydroxy-, Alkoxy-, and Benzyloxyarenes by Potassium Thiocyanate and Silica Sulfuric Acid as a Cyanating Agent}, series = {The journal of organic chemistry}, volume = {84}, journal = {The journal of organic chemistry}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {0022-3263}, doi = {10.1021/acs.joc.8b02191}, pages = {1748 -- 1756}, year = {2019}, abstract = {A novel and efficient metal- and solvent-free regioselective para-C-H cyanation of hydroxy-, alkoxy-, and benzyloxyarene derivatives has been introduced, using nontoxic potassium thiocyanate as a cyanating reagent in the presence of silica sulfuric acid (SSA). The desired products are obtained in good to high yields without any toxic byproducts.}, language = {en} } @article{RyppaSengeHatscheretal.2005, author = {Ryppa, C. and Senge, Mathias O. and Hatscher, S. S. and Kleinpeter, Erich and Wacker, Philipp and Schilde, Uwe and Wiehe, A.}, title = {Synthesis of mono- and disubstituted porphyrins : A- and 5,10-A(2)-type systems}, issn = {0947-6539}, year = {2005}, abstract = {General syntheses have been developed for meso-substituted porphyrins with one or two substituents in the 5,10- positions and no beta substituents. 5-Substituted porphyrins with only one meso substituent are easily prepared by an acid-catalyzed condensation of dipyrromethane, pyrrole-2-carbaldehyde. and an appropriate aldehyde using a "[2+1+1]" approach. Similarly, 5,10-disubstituted porphyrins are accessible by simple condensation of unsubstituted tripyrrane with pyrrole and various aldehydes using a "[3+1]" approach. The yields for these reactions are low to moderate and additional formation of either di- or mono-substituted porphyrins due to scrambling of the intermediates is observed. However, the reactions can be performed quite easily and the desired target compounds are easily removed due to large differences in solubility. A complementary and more selective synthesis involves the use of organolithium reagents for SNAr reactions. Reaction of in situ generated porphyrin (porphine) with 1.1-8 equivalents of RLi gave the monosubstituted porphyrins, while reaction with 3-6 equivalents of RLi gave the 5,10-disubstituted porphyrins in yields ranging from 43 to 90\%. These hitherto almost inaccessible compounds complete the series of different homologues of A-, 5,15-A(2)-, 5,10-A(2)-, A(3)-, and A(4)-type porphyrin's and allow an investigation of the gradual influence of type, number, and regiochemical arrangement of substituents on the properties of meso-substituted porphyrins. They also present important starting materials for the synthesis of ABCD porphyrins and are potential synthons for supramolecular materials requiring specific substituent orientations}, language = {en} } @article{ReicheStarkeKleinpeteretal.1999, author = {Reiche, K. B. and Starke, Ines and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen and Pihlaja, Kalevi and Oksaman, P. and Ovcharenko, V. V.}, title = {Fragmentation of imine-type meta-bridged bis(benzo crown ether)s under electron impact}, year = {1999}, language = {en} } @article{ReicheStarkeKleinpeteretal.1998, author = {Reiche, K. B. and Starke, Ines and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen}, title = {Host-guest complexation of imine-type meta-bridged bis(benzo crown ether)s with alkali cations in the gas phase under FAB conditions}, year = {1998}, language = {en} } @article{RasovicSteelKleinpeteretal.2007, author = {Rasovic, Aleksandar and Steel, Peter J. and Kleinpeter, Erich and Markovic, Rade}, title = {Regioselective synthesis of 1,3-thiazines by sequential 4-oxothiazolidine to 1,2-dithiole to 1,3-thiazine transformations : role of intramolecular non-bonded S...O interactions}, doi = {10.1016/j.tet.2006.12.075}, year = {2007}, abstract = {A new synthetic approach to 2,3-dihydro-4H-1,3-thiazine derivatives based upon reductive rearrangement of 1,2- dithiole-3-ylidene thiones has been developed. In turn, the 1,2-dithiole derivatives were prepared by an efficient ring- opening-closing process of 2-alkylidene-4-oxothiazolidines, induced in the presence of Lawesson's reagent by intramolecular non-bonded 1,5-type S...O interactions in the 4-oxothiazolidine precursors.}, language = {en} }