@article{BelasriTopalHeydenreichetal.2020, author = {Belasri, Khadija and Topal, Leila and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Fulop, Ferenc and Szatmari, Istvan}, title = {Synthesis and conformational analysis of naphthoxazine-fused phenanthrene derivatives}, series = {Molecules}, volume = {25}, journal = {Molecules}, number = {11}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules25112524}, pages = {15}, year = {2020}, abstract = {The synthesis of new phenanthr[9,10-e][1,3]oxazines was achieved by the direct coupling of 9-phenanthrol with cyclic imines in the modified aza-Friedel-Crafts reaction followed by the ring closure of the resulting bifunctional aminophenanthrols with formaldehyde. Aminophenanthrol-type Mannich bases were synthesised and transformed to phenanthr[9,10-e][1,3]oxazines via [4 + 2] cycloaddition. Detailed NMR structural analyses of the new polyheterocycles as well as conformational studies including Density Functional Theory (DFT) modelling were performed. The relative stability of ortho-quinone methides (o-QMs) was calculated, the geometries obtained were compared with the experimentally determined NMR structures, and thereby, the regioselectivity of the reactions has been assigned.}, language = {en} } @article{CsuetoertoekiSzatmariKochetal.2012, author = {Cs{\"u}t{\"o}rt{\"o}ki, Renata and Szatmari, Istvan and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc}, title = {Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c] quinazolin-13-ones}, series = {Tetrahedron}, volume = {68}, journal = {Tetrahedron}, number = {24}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2012.04.026}, pages = {4600 -- 4608}, year = {2012}, abstract = {The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A(1), but also the rearranged chain form A(2) as a new tautomer were detected in DMSO at room temperature. The quantity of A(2) in the tautomeric mixture was changed with time. Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS.}, language = {en} } @article{CsuetoertoekiSzatmariKochetal.2011, author = {Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc}, title = {Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives}, issn = {0040-4020}, year = {2011}, language = {en} } @article{HeydenreichKochKlodetal.2006, author = {Heydenreich, Matthias and Koch, Andreas and Klod, Sabrina and Szatmari, Istvan and Fulop, Ferenc and Kleinpeter, Erich}, title = {Synthesis and conformational analysis of naphth[1', 2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine and naphth[1', 2':5,6][1,3]oxazino[3,4-c][1,3]benzoxazine derivatives}, series = {Tetrahedron}, volume = {62}, journal = {Tetrahedron}, number = {48}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-4020}, doi = {10.1016/j.tet.2006.09.037}, pages = {11081 -- 11089}, year = {2006}, abstract = {A new functional group, the hydroxy group, was inserted into a Betti base by reaction with salicylaldehyde, and the naphthoxazine derivatives thus obtained were converted by ring-closure reactions with formaldehyde, acetaldehyde, propionaldehyde or phosgene to the corresponding naphth[1',2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine derivatives. Further, the conformational analysis of these polycyclic compounds by NMR spectroscopy and an accompanying molecular modelling are reported; especially, both quantitative anisotropic ring current effects of the aromatic moieties in these compounds and steric substituent effects were employed to determine the stereochemistry of the naphthoxazinobenzoxazine derivatives.}, language = {en} } @article{HeydenreichKochSzatmarietal.2008, author = {Heydenreich, Matthias and Koch, Andreas and Szatm{\´a}ri, Istv{\´a}n and Fulop, Ferenc and Kleinpeter, Erich}, title = {Synthesis and conformational analysis of naphth[1,2-e][1,3]oxazino[4,3-a][1,3]isoquinoline and naphth[2,1- e][1,3]oxazino[4,3-a]isoquinoline derivatives}, doi = {10.1016/j.tet.2008.05.025}, year = {2008}, abstract = {Through the cyclization of 1-(;-hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinoline and 1-(;- hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinoline with formaldehyde, phosgene, p-nitrobenzaldehyde or p-chlorophenyl isothiocyanate, 8-substituted 10,11-dihydro-8H,15bH-naphth[1,2-e][1,3]oxazino[4,3-a]isoquinolines (3 and 4) and 10,11- dihydro-8H,15bH-naphth[2,1-e][1,3]oxazino[4,3-a]isoquinolines (15 and 16) were prepared. Conformational analysis of both the piperidine and the 1,3-oxazine moieties of these heterocycles by NMR spectroscopy and an accompanying theoretical study revealed that these two conformationally flexible six-membered ring moieties prefer twisted chair conformers.}, language = {en} } @article{KleinpeterCsuetoertoekiSzatmarietal.2012, author = {Kleinpeter, Erich and Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Heydenreich, Matthias and Koch, Andreas and Starke, Ines and Fulop, Ferenc}, title = {Novel piperidine-fused benzoxazino- and quinazolinonaphthoxazines-synthesis and conformational study}, issn = {0040-4020}, year = {2012}, abstract = {The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl)methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzoxazinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, Gtct1 for 4 and Gtct1 for 7, were corroborated by spatial NOE information relating to the H7a-H10a-H15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements.}, language = {en} } @article{KleinpeterCsuetoertoekiSzatmarietal.2012, author = {Kleinpeter, Erich and Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Koch, Andreas and Fulop, Ferenc}, title = {Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-ones}, year = {2012}, abstract = {The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A1, but also the rearranged chain form A2 as a new tautomer were detected in DMSO at room temperature. The quantity of A2 in the tautomeric mixture was changed with time. Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS.}, language = {en} } @article{KleinpeterSzatmariLazaretal.2009, author = {Kleinpeter, Erich and Szatm{\´a}ri, Istv{\´a}n and L{\´a}z{\´a}r, L{\´a}szl{\´o} and Koch, Andreas and Heydenreich, Matthias and Fulop, Ferenc}, title = {Visualization and quantification of anisotropic effects on the 1H NMR spectra of 1,3-oxazino[4,3- alpha]isoquinolines - indirect estimates of steric compression}, issn = {0040-4020}, doi = {10.1016/j.tet.2009.07.038}, year = {2009}, abstract = {The anisotropic effects of the phenyl, alpha- and beta-naphthyl moieties in four series of 1,3-oxazino[4,3- a]isoquinolines on the H-1 chemical shifts of the isoquinoline protons were calculated by employing the Nucleus Independent Chemical Shift (NICS) concept and Visualized as anisotropic cones by a through-space NMR shielding grid. The signs and extents of these spatial effects on the H-1 chemical shifts of the isoquinoline protons were compared with the experimental H-1 NMR spectra. The differences between the experimental delta (H-1)/ppm values and the calculated anisotropic effects of the aromatic moieties are discussed in terms of the steric compression that occurs in the Compounds studied.}, language = {en} } @article{LaemmermannSzatmariFulopetal.2009, author = {L{\"a}mmermann, Anica and Szatm{\´a}ri, Istv{\´a}n and Fulop, Ferenc and Kleinpeter, Erich}, title = {Inter- or intramolecular N···H-O or N-H···O Hydrogen bonding in 1,3-Amino-alpha/beta-naphthols : an experimental NMR and computational study}, issn = {1089-5639}, doi = {10.1021/Jp902731n}, year = {2009}, abstract = {The existence of intermolecular or intramolecular N···H;O or N;H···O hydrogen bonding in three series (series 1, substituted 1-aminoalkyl-2-naphthols: R = H, Me, Et, Pr, i-Pr; series 2, substituted 1-;- aminobenzyl-2-naphthols: H, p-OMe, p-F, p-Cl, p-Br, p-NO2, p-Me; series 3, substituted 2-;-aminobenzyl-1-naphthols: R = H, p-Me, p-F, p-Br, p-OMe, m-NO2, m-Br) are studied by NMR spectroscopy and computed at the DFT level of theory [B3LYP/6-311+G(d,p)]. The correct nature of the H-bond was assigned unequivocally both experimentally and computationally by potential energy scans rotating the involved dihedral angles. We investigated the effects of substituents on the strength of the H-bond by evaluating the corresponding hyperconjugative stabilization energy nlonepair ; ;*X;H and Hammett substituent constant plots. By this means, steric and electronic substituent effects could be easily quantified and separated.}, language = {en} } @article{NeuvonenFulopNeuvonenetal.2008, author = {Neuvonen, Helmi and Fulop, Ferenc and Neuvonen, Kari and Koch, Andreas and Kleinpeter, Erich}, title = {Electronic effects of heterocyclic ring systems as evaluated with the aid of 13C and 15N NMR chemical shifts and NBO analysis}, doi = {10.1002/Poc.1271}, year = {2008}, abstract = {The electronic effects of the 5- and 6-membered heterocyclic rings on the C=N-N unit of five different hydrazone derivatives of pyridine-2-, -3- and -4-carbaldehydes, pyrrole-2-carbaldehyde, furan-2- and -3-carbaldehydes and thiophene-2- and -3-carbaldehydes have been studied with the aid of 13C and 15N NMR measurements together with the natural bond orbital (NBO) analysis. As model compounds are used the corresponding substituted benzaldehyde derivatives. The polarization of the C=N unit of the hydrazone functionality of the heteroaryl derivatives occurs in an analogous manner with that of phenyl derivatives. The electron-withdrawing heteroaryl groups destabilize and the electron-donating groups stabilize the positive charge development at the CN carbon while the effect on the negative charge development is opposite. The 15N NMR chemical shift of the C=N and C=N-N nitrogens and the NBO charges at C=N-N unit can be correlated with the replacement substituent constants of the heteroaryl groups. 13C NMR shifts of the C=N carbon of N,N- dialkylhydrazones of the heteroarenecarbaldehydes can be correlated with a dual parameter equation possessing the polar substituent constant ;* of the heteroaryl group and the electronegativity of the heteroatom as variables.}, language = {en} } @article{NeuvonenFulopNeuvonenetal.2005, author = {Neuvonen, Kari and Fulop, Ferenc and Neuvonen, Helmi and Koch, Andreas and Kleinpeter, Erich and Pihlaja, Kalevi}, title = {Propagation of polar substituent effects in 1-(substituted phenyl)-6,7-dimethoxy-3,4-dihydro- and -1,2,3,4- tetrahydroisoquinolines as explained by resonance polarization concept}, year = {2005}, abstract = {Propagation of inductive and resonance effects of phenyl substituents within 1-(substituted phenyl)-6,7- dimethoxy-3,4-dihydro- and -1,2,3,4-tetrahydroisoquinolines were studied with the aid of C-13 and N-15 NMR chemical shifts and ab initio calculations. The substituent-induced changes in the chemical shift (SCS) were correlated with a dual substituent parameter equation. The contributions of conjugative (rho(R)) and nonconjugative effects (rho(F)) were analyzed, and mapping of the substituent-induced changes is given over the entire isoquinoline moiety for both series. The experimental results can be rationalized with the aid of the resonance polarization concept. This means the consideration of the substituent-sensitive balance of different resonance structures, i.e., electron delocalization, and the effect of the aromatic ring substituents on their relative contributions. With tetrahydroisoquinolines, the delocalization of the nitrogen lone pair (stereoelectronic effect) particularly contributes. Correlation analysis of the Mulliken atomic charges for the dihydroisoquinoline derivatives was also performed. The results support the concept of the substituent-sensitive polarization of the isoquinoline moiety even if the polarization pattern achieved via the NMR approach is not quite the same as that predicted by the computational charges. Previously the concepts of localized pi- polarization and extended polarization have been used to explain polar substituent effects within aromatic side-chain derivatives. We consider that the resonance polarization model effectively contributes to the understanding of the polar substituent 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{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{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{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{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{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{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} }