摘要:

AbstractThe1H and13C NMR spectra of a series ofn‐alkanes (C5‐C32) were measured in CCl4, CDCl3, C6D6, C6H5Cl and C6D5CD3and the aromatic solvent‐induced shifts (ASIS) are discussed. The chemical shifts of the inner methylene protons show a steady downfield shift as the carbon number of then‐alkane increases, while the shifts of the methyl protons are smaller than those of the inner methylene protons in aromatic solvents. The ASIS of the outer carbons are larger than those of the inner carbons up to the sixth carbon from the end. The ASIS of the sixth and further inner carbons of the short chains are larger than those of the long chains. These results suggest thatn‐alkanes have a folded structure in aromatic solvents and that the degree of folding increases with increasing cha

ISSN:0749-1581    

DOI:10.1002/mrc.1260280502

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractNitrogen quaternization in the analgesic nefopam [(±)‐3,4,5,6‐tetrahydro‐5‐methyl‐1‐phenyl‐1H‐2,5,‐ benzoxazocine hydrochloride] by eitherN‐trideuteriomethylation orN‐oxidation affords reaction product diastereomeric mixtures differing inN‐configuration. The axial to equatorialN‐CH3product ratios were found to beca.3:2 (N‐trideuteriomethylation) and approximately equimolar (ca.48:52,N‐oxidation). Both diastereomericN‐oxides have boat‐(flattened chair) conformations of the octagonal ring in which the phenyl group isexo‐oriented. The quaternary ammonium salts showed considerable line broadening in the1H NMR spectrum owing to rapid conformational equilibration. The same boat‐(flattened chair) conformation is clearly the preponderant contributor to the time‐averaged structure of nefopam methiodide in CD2Cl2solution, similar to the case for the equatorialN‐methyl isomer of the parent hydrochloride salt. Conformational assignments were based on the vicinal coupling constants in the —OCH2CH2N—fragment and on the finding of an NOE intensity enhancement for the benzhydrylic‐H

ISSN:0749-1581    

DOI:10.1002/mrc.1260280503

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of substituents on13C and1H NMR chemical shifts in 2‐ and 3‐substituted furans, thiophenes, seleno‐phenes and tellurophenes was studied by means of principal components analysis (PCA) and partial least squares (PLS) analysis. The analysis of the data by PCA showed that for both series the substituents are grouped into four different classes depending on the heteroatom present in the ring, and that the substituent‐heteroatom interaction has the same nature for all the rings. PLS analysis of the data sets allowed the prediction of the chemical shift values of a different ring having the same subst

ISSN:0749-1581    

DOI:10.1002/mrc.1260280504

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe15N,13C and1H NMR spectra of 2:1 cobalt(III) complexes of azo dyes and their15N isotopomers, derived from substituted 2‐hydroxyaniline azo coupling products with acetoacetanilide, were measured. It was found that, in contrast to precursors existing fully in their hydrazone forms, 2:1 cobalt(III) complexes exist in (E)‐azo configurations, cobalt being bound to oxygens which originate in hydroxy and amide groups and nitrogen from substituted anilines as starting mater

ISSN:0749-1581    

DOI:10.1002/mrc.1260280505

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractFluorine NMR spectra of 23 9α‐fluorocorticosteroid analogs established that the 9α‐fluorine is subject to deshielding effects by remote structural features (A‐ring olefinic unsaturation, A‐ring 1α‐ and 2β‐hydroxy and acetoxy features and D‐ring 16α‐methyl substitution) and to minor shielding effects by vicinal 11β‐alcohol dehydrogenation and acetylation, and by B‐ring olefinic unsaturation. Substitutions in the 6α‐, 6β‐, 16α‐ and 16β‐positions and D‐ring homoannulation do not alter the19F chemical shift significantly. Coupling constants of the 9α‐fluorine to vicinal 8β‐ and 11α‐hydrogens are not altered appreciably by structural changes, except for introduction of a Δ6‐double bond or 11β‐alcohol dehydrogenation, indicating that the conformations of the tetracyclic ring system and particularly the B/C‐rin

ISSN:0749-1581    

DOI:10.1002/mrc.1260280506

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractReaction of 2‐methyl‐3‐thiocyanatocrotonaldehyde with aniline hydrochloride and subsequent addition of dicyclohexylamine afforded a new 6a‐thia(SIV)‐1,6‐diazapentalene. The presence of the NSN bond was verified through the N 1s and S 2p binding energies and the nitrogen‐nitrogen coupling constant in the doubly15N‐labelled compound, prepared by using [15N]an

ISSN:0749-1581    

DOI:10.1002/mrc.1260280507

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe stereochemistry of benzannelated 1,6‐diazabicyclo[4.2.1]octa‐3,7‐dienes (the conformation of the eight‐membered ring and of the variable substituents on the methylene bridge) was determined by means of NOE enhancements and stereospecific long‐range H,H coupling constants in the relevant NM

ISSN:0749-1581    

DOI:10.1002/mrc.1260280508

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractPerhydropyrido[1,2‐c][1,3]thiazepine adopts (CDCl3solution, 25°C) an equilibrium containing>98%trans‐fused conformer, in contrast to perhydropyrido[1,2‐c][1,3]oxazepine, which adopts aca.74%trans‐fused ⇌ 26%O‐inside‐cis‐fused conformational equilibrium. Thecis‐(H‐5a, H‐8)‐8‐ethyl‐substituted derivatives of both systems show increased preference for theS/Oinsidecisconformations. The related 2‐tert‐butylperhydropyrido[1,2‐c][1,3]diazepine adopts predomi

ISSN:0749-1581    

DOI:10.1002/mrc.1260280509

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe configurations and conformations of diastereoisomeric 1‐(decahydroquinolin‐8‐yl)butan‐2‐ols and of perhydropyrido[3,2,1‐j,k][3,1]benzoxazepines resulting from ring closure of these compounds with formaldehyde have been assigned by1H and13C NMR s

ISSN:0749-1581    

DOI:10.1002/mrc.1260280510

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe3Δ‐deuterium isotope effects of partially and fully deuteriatedtert‐butyl groups on the13C NMR spectra oftert‐butylbenzene and derivatives are discussed in detail. It is shown that they correlate with the chemical shift of C‐1 of the aromatic ring. It has been demonstrated that when deuterium is replaced with some other substituents, the SCS values of these substituents show a parallel behaviour to the deuterium isotope effects. It is concluded that, for the compounds studied, deuterium isotope effects and substituent chemical shifts can be described on a comm

ISSN:0749-1581    

DOI:10.1002/mrc.1260280511

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY