摘要:

AbstractThe 22.63 MHz13C NMR spectra of a series of alkylated thioureas are reported. CharacteristicZandEspectral regions were found for the13C  S resonances. The two regions were generally found to be non‐overlapping for the series, with the region of theZ,Zresonances occurring more downfield than those of either theZ,EorE,Zconformers in the cases of 1,3‐disubstitution. TheZ,Zconfiguration became favored and the relative chemical shift difference (Rδ) increased linearly with increasing substituent size. At 217 K, hindered internal rotation caused a multiplicity of resonances which were normally single peaks in the broad band1H decoupled 62.86 MHz13C spectrum of CH3NHCSNH(CH2)2NHCSNHCH3(2MTE) at room temperature. The trends in chemical shifts and populations were employed to assign tentatively the resonances of five of the six possible configurational isomers contributing to the 2MTE spectra at 217 K. The isomer populations are given. The13C NMR spectra reported here led to signal assignments ofZandEisomers which supported prior1H NMR results and contradicted more recent results of another13C NMR study ofN‐methylthiourea. The major peak of the exchange doublet occurs at relatively high field strengths in both met

ISSN:0030-4921    

DOI:10.1002/omr.1270210502

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra were recorded for isoxazolines and isoxazolidines from 2,4,6‐trimethylbenzonitrile oxide or α‐phenyl‐N‐phenyl nitrone as dipolarophiles with the thiophene and benzo[b]thiopheneS‐oxide andS,S‐dioxide series. The effects of the isoxazoline or isoxazolidine groups are not very different. Owing to the electronegativity of the oxygen atom, the main influence arises from the regioselectivity of the addition to the carbon atoms located at the α or β position

ISSN:0030-4921    

DOI:10.1002/omr.1270210503

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR signals were assigned for the complete set of the 26 theoretically possible isomers of methyl 5β‐cholanates having one to three hydroxy groups at positions C‐3, C‐7 and/or C‐12 in the nucleus. Substituent effects on the13C NMR shielding data serving to characterize the position and configuration of the hydroxy groups are

ISSN:0030-4921    

DOI:10.1002/omr.1270210504

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractAnalyses of the1H NMR spectra of fluorene, 2‐nitrofluorene, 1‐azafluorene, 2‐azafluorene, 4‐azafluorene, 7‐nitro‐4‐azafluorene and 1,4‐diazafuorene have been carried out using computer calculations and homo double resonance techniques. The relative signs and magnitude of the4J,5Jand6Jlong‐range coupling constants of the 9‐CH2group protons with the pyridine and phenylene ring protons have been measured by five‐ and six‐spin calculations. It was established that the presence of substituents and the N heteroatom has only a very weak effect on the values and signs of these coupling constants. The usual alternating signs of long‐range coupling constants involving π‐electron systems were confirmed, giving negative signs for even and positive signs for odd numbers of bonds sep

ISSN:0030-4921    

DOI:10.1002/omr.1270210505

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe analysis of the1H NMR spectra of 2,8‐dithia‐1,5‐diphosphabicyclo[3.3.0]octane, 2,8‐dithia‐1‐phospha‐5‐azabicyclo[3.3.0]octane and 2,8‐dithia‐1‐arsa‐5‐phosphabicyclo[3.3.0]octane is supported by means of 2D‐J‐resolved NMR measurements. The spectra suggest a preferred conformer with strong puckering of

ISSN:0030-4921    

DOI:10.1002/omr.1270210506

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR spectra of 1,4‐benzodiazepines, substituted differently at C‐7, are reported. With increasing electron demand of the substituent the signal of C‐2 is shifted upfield, an effect which is interpreted in terms of a π‐polarization of the carbonyl π‐electrons. This mechanism also seems to be of importance for the π‐electrons of the 5‐phenyl substituent and of the (N‐4)(C‐5) bond. Owing to the formation of hydrogen‐bonded self‐associates, compounds with a free amide group show concentration‐dependent shifts of some resonances. This is most obvious for C‐2, the proposed proton accepting site f

ISSN:0030-4921    

DOI:10.1002/omr.1270210507

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe1H and13C NMR chemical shifts of dibenzo[b,f]pentalene and its 5,10‐dimethyl derivative are presented and compared with those of the corresponding dilithium dianions. As probed by the relative13C NMR chemical shifts, the charge distribution within the dianion system is clearly dependent on the actual ion pair state. This condition is demonstrated by varying the solvent and temperature. The polarization of charge towards the pentalene carbons, i.e. the preferred cation positions, is observed on going to tight ion pair conditions. Further support for this model is gained from7Li NMR. The limitations of the use of1H and13C NMR chemical shifts to measure charge distributions within anion systems are discusse

ISSN:0030-4921    

DOI:10.1002/omr.1270210508

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe solution conformation of L‐6‐methylperhydroimidazo[1,5‐c]thiazole‐5,7‐dione (γ‐thiaprolinehydantoin) has been determined from an extensive1H and13C NMR study, allowing the extraction of vicinal inter‐proton and carbon‐hydrogen coupling constants. The major conformation of the thiazolidine ring is an envelope with C‐δ as the flapexo(δ−). In solution the preferred solid state (twist) conformer with C‐αexoand C‐βendo(αβT) is only a minor contributor.13C spin–lattice relaxation data reveal the flex

ISSN:0030-4921    

DOI:10.1002/omr.1270210509

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe conformations of thecisandtransisomers of 4,6‐diphenyl‐, 4,5‐diphenyl‐ and 5,6‐diphenyltetrahydro‐1,3‐oxazin‐2‐one and 4,5‐diphenylhexahydropyrimidin‐2‐one, and of some of theirN‐substituted derivatives, have been studied by1H NMR. Conformers with 4a, 6e‐, 4a, 5e‐ and 5a, 6e‐phenyl groups are preferred in the respective isomers of the N‐H oxazinones, confirming a half‐chair conformation of the ring. Allylic strain caused byN‐substituents shifts strongly the a,e⇌e, a equilibria intrans‐4,6‐diphenyl‐ andcis‐4,5‐diphenyl‐oxazinones, but only moderately the e,e⇌a,a equilibria in the compounds withtrans‐vicinal phenyl groups. In the latter, the diaxial conformation is preferred only in the case of bulkyN‐substituents. The diaxial conforma

ISSN:0030-4921    

DOI:10.1002/omr.1270210510

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract1H NMR Parameters are reported for five 1,4‐dithiepan‐6‐ones. 1,4‐Dithiepan‐6‐one 1‐oxide exists in solution as an equilibrium involving two different twist‐chair conformations, which contrasts with its conformational behaviour in the solid state. Twist‐chair conformers are also adopted by other members of the series, the favoured form varying with ring substitution. The SO bond in 1,4‐dithiepan‐6‐one 1‐oxide and in its 5,5‐dimethyl analogue exhibit a prefer

ISSN:0030-4921    

DOI:10.1002/omr.1270210511

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY