摘要:

AbstractThe1H NMR parameters of methyl 3‐substitutedcis‐4‐halotetrahydro‐2‐oxo‐3‐furancarboxylates are reported, with assignments of the ring protons based on solvent‐induced changes in the vicinaltranscoupling constants,3J(H‐4, H‐5). Preferred conformations,cewith a pseudo‐equatorial halogen for thecisisomers andtawith a pseudo‐axial halogen for thetransisomers, have been suggested on comparison of the magnitudes ofJ(trans)andJ(gem)in both series. The3J(13CH3, H‐4) values measured for methylcis‐4‐bromotetrahydro‐3‐methyl‐3‐furancarboxylate, methyltrans‐4‐bromotetrahydro‐3‐methyl‐3‐furancarboxylate andtrans‐3,4‐dibromodihydro‐3‐methyl‐2

ISSN:0030-4921    

DOI:10.1002/omr.1270210302

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of singly15N‐labelledZ/Eisomers of azo and diazo compounds were recorded. The1J(13C15N) coupling constants are strongly dependent on the geometrical configuration of the azo group, the relative position of the lone pair of electrons at the non‐coupling azo nitrogen atom having a decisive influe

ISSN:0030-4921    

DOI:10.1002/omr.1270210303

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of 5,8‐quinolinedione, 6‐chloro‐5,8‐quinolinedione and 7‐chloro‐5,8‐quinolinedione have been examined in detail. Utilization of long‐range proton‐carbon coupling constants have allowed the unambiguous identification of the regioisomeric 8‐aza‐1,2,3,4‐tetrahydrobenz[a]anthracene‐7,12‐dione and 11‐aza‐1,2,3,4‐tetra

ISSN:0030-4921    

DOI:10.1002/omr.1270210304

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C13C spin coupling constants have been determined in substituted [1‐13C]tetrahydronaphthylenes, [5‐13C]hexahydrobenzanthracenes and [5‐13C]benzanthracene. In addition, the13C13C spin coupling constants for 7‐hydroxy[7‐13C]benzopyrene,trans‐7,8‐dihydro[7‐13C]benzopyrene‐7,8‐diol andtrans‐7,8‐dihydro[10‐13C]benzopyrene‐7,8‐diol are reported, together with the one‐bond carbon‐carbon coupling constants between C‐4 and C‐5 in selected 4,5‐disubstituted benzopyrenes. Values for the directly bonded coupling constants and long‐range coupling constants are similar to those reported previously for other aromatic and aliphatic systems. Substituent effects on carbon‐carbon coupling are compared for s

ISSN:0030-4921    

DOI:10.1002/omr.1270210305

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract13C chemical shifts are reported for the ring carbons of several substituted Δ1‐pyrrolines. Average values for methine and methylene ring carbons facilitate structure elucidation of substituted δ1‐pyrrolines by13C NMR spectro

ISSN:0030-4921    

DOI:10.1002/omr.1270210306

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract17O chemical shifts of axial hydroxyl groups in cyclohexanols are upfield of those of corresponding equatorial groups, but in 5‐hydroxy‐1,3‐dioxanes the opposite is observed: the axial OH resonates downfield of the equatorial OH. The situation is the same in the corresponding methyl ethers and is, thus, not a result of intramolecular hydrogen bonding in the axial 5‐hydroxy‐1,3‐dioxane, but appears to parallel the effect on13C and19F shifts observed in corresponding equatorial and axial 5‐methyl‐ and 5‐fluoro‐1,3‐dioxanes, which has been attributed to an upfield shifting effect of the antiperiplanar γ‐located heteroatoms. Surprisingly, the reciprocal effect is not seen in the ring17O shifts of the 5‐hydroxy‐1,3‐dioxanes. A δ compression shift is seen in the17O spectrum oftrans‐3,3,5‐trimethylcyclohexanol (syn‐axial OH and CH3), analogous to the effect earlier reported in13C spectra. Conversion of four of the alcohols to methyl ethers produces a large upfield effect on the17O shift, larger in the cyclohexanols than in the 1,3‐dioxane‐5‐ols. Similar upfield shifts have been recorded in the literature; their extent depends on whether the

ISSN:0030-4921    

DOI:10.1002/omr.1270210307

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe enantiomeric composition of derivatives of new classes of optically active sulphur compounds (variously substituted sulphoxides, sulphoximes, sulphilimines) has been readily determined with the aid of chiral europium shift reagents.

ISSN:0030-4921    

DOI:10.1002/omr.1270210308

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractA comparative study of the13C NMR spectra of benzothiazinone and benzothiazepinone dioxide derivatives and of some structurally related benzosulphonamides is presented. The size of the heterocyclic ring is reflected in the13C chemical shifts and in the one‐bond carbon‐proton aromatic coupling constants. An upfield γ‐effect of sulphur on the13C chemical shifts inN‐substituted carboxyethylbenzene‐4,5‐dimethoxysulphonamides

ISSN:0030-4921    

DOI:10.1002/omr.1270210309

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractTwo 1,4‐benzodiazepinones of psychopharmacological interest, pinazepam (2) and prazepam (3), were studied in solution by13C and1H NMR.1H variable‐temperature experiments showed that the seven‐membered ring exists in a simple pseudo‐boat form at room temperature, but the energy barrier is higher in 3 (ΔG405°c= 82.8 kJ mol−1) than in diazepam (1). Moreover, upon addition of LSR, the boat conformation is retained in the lanthanide ion‐substrate complex, as with 1 in the solid state. Using a concentration‐dependent shift technique and a computer‐assisted LIS method, the conformations of theN‐branched side‐chain were investigated. Two preferred orientations were found for the propargyl group of 2, while three unequally populated conformations of the cyclopropyl moiety of 3 are distributed preferentially in the sterically unhindered spa

ISSN:0030-4921    

DOI:10.1002/omr.1270210310

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract1H and77Se spin‐lattice relaxation times have been measured for the series of organochalcogen compounds MeE(CH2)nEMe (E=S, Se,n=0–3; E = O,n= 1, 2). The methyl and methylene protonT1values decreased with increasing mass/size of the chalcogen and with increasing methylene chain length. The values are primarily due to intra‐ and inter‐molecular dipole‐dipole relaxation with proton‐proton cross‐relaxation effects playing a significant role.77SeT1values are dominated by spin rotation and chemical shielding anisotropy mechanisms, their relative importance depending on the size of the molecule and temperature o

ISSN:0030-4921    

DOI:10.1002/omr.1270210311

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY