摘要:

Abstract2‐Isopropyl‐6‐phenyl‐ and 2,6‐diisopropyl‐pyridiniums with bulky 1‐substituents show temperature‐variable NMR spectra which are interpreted in terms of restricted rotation. 2‐Isopropyl‐4,6‐diphenylpyrylium can be deprotonated at the isopropyl group to give an anhydro base which forms new pyryliu

ISSN:0030-4921    

DOI:10.1002/omr.1270211002

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract13C nuclear magnetic resonance spectra were collected for a series of 5‐ and 6‐monoaromatic ring‐substituted benzonorbornadienes and 5‐, 6‐, 7‐, and 8‐monosubstituted benzonorbornen‐2‐ones.13C chemical shifts values were found to be useful in the differentiation of the four monosubstituted aromatic ring isomers of benzonorbornen‐2‐one (1). We found that the13C NMR spectrum of a substituted benzonorbornen‐2‐one (A) could be predicted with good accuracy (R2for each aromatic carbon ≥ 0.925) from a knowledge of the13C NMR spectrum of 1 and the appropriately substituted benzene. The substituents studied were NO2, NH2, I, CF3, CN, OCH3, and H. Correlation analysis showed that the carbonyl in A was effectively insul

ISSN:0030-4921    

DOI:10.1002/omr.1270211003

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract1,3,5‐Trineopentylbenzenes (TNB) with one or two benzylic substituents in each neopentyl group were synthesized. The substituents were F, Cl, Br, J, OCH3, OCOCH3, OSi(CH3)3and CH3and, in cases of disubstitution, F, Cl, Br, CH3and Cl, CH3and Br and SCH2CH2S. Barriers to internal Csp3Csp2(aryl) and Csp3Csp3rotation were estimated by13C and19F NMR band shape methods. Estimated barriers in the TNB series were found to be very close to those found for the corresponding mononeopentylbenzenes. For some of the compounds studied, molecular mechanics (MM) calculations were performed with the Allinger MMP1 program. Differences between calculated and experimental estimated barriers were found, and possible sources of these discrepancies in terms of parameters used in the MMP1 program are

ISSN:0030-4921    

DOI:10.1002/omr.1270211004

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract17O NMR chemical shifts and calculated (ab initioMO theory) electron densities are reported for a series ofpara‐substituted acetophenones, XC4H6COCH3, where X = NH2, OCH3, F, Cl, CH3, H, COCH3, CN, NO2. The17O shifts are very sensitive to theparasubstituent and cover a range of some 51 ppm. Donors induce upfield shifts and acceptors downfield shifts. The substituent chemical shifts (SCS) correlate precisely with σIand σR+using the Dual Substituent Parameter (DSP) method. The derived transmission coefficients ρIand ρRindicate that polar and resonance mechanisms contribute approximately equally to the observed substituent effects. The shifts also correlate well with calculated π‐electron densities (slope = 1500 ppm per electron) confirming their electronic origin. λ msxn→π*values are also reported, and the role of the average excitation energy, ΔE, in determining17O SCS values is discussed. It is concluded that variations in ΔEare minor and that the local Δ‐electron density is the dominant feature co

ISSN:0030-4921    

DOI:10.1002/omr.1270211005

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractNitrogen‐15 NMR data are reported for ten benzodiazepines, including the chemically useful drugs diazepam, oxazepam, clonazepam, flurazepam and chlordiazepoxide. Substituent effects for neighboring groups are presented and discusse

ISSN:0030-4921    

DOI:10.1002/omr.1270211006

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractA new method based on the combination of selective proton decoupling and INEPT is explained in detail. This technique, named selective INEPT (SEL‐INEPT), is a useful and sensitive method for the13C NMR assignment of methylene carbons with non‐equivalent protons. The13C NMR spectrum of monensin has been analysed by the application of this techni

ISSN:0030-4921    

DOI:10.1002/omr.1270211007

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe1H and13C spectra ofp‐substituted 1,3,5‐triarylbenzenes, 7‐ andp‐substituted 1,3,9‐triaryl‐9‐methyl‐fluorenes and 2‐, 10‐ andp‐substituted 6,12,13a‐triaryl‐12‐methylbenzo(6,7)cycloheptadieno[1,2,3‐jk]fluorenes have been examined.p‐Substituents were methoxy, methyl and fluorine groups. The1H spectra were recorded at 300 MHz and permitted assignments for the aromatic protons by selective proton decouplings. Partial assignment of the carbon atoms in t

ISSN:0030-4921    

DOI:10.1002/omr.1270211008

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractSome applications illustrating the use of zinc (II)meso‐tetraphenylporphyrin (ZnTPP) as a diamagnetic shift reagent are described. The complexation shifts (ΔP) in a series of substituted pyridines are shown to be determined by both the basicity of the coordinating nitrogen atom and steric effects ofortho‐substituents. The selectivity of ZnTPP (N»O) in the simplification of the spectra of multifunctional ligands is demonstrated. Addition of the reagent neither affects the rotamer populations of the Inderal side‐chain nor produces any distortion of the 2‐benzylmorpholine ring. In addition, the substrate‐reagent solution may be shaken with D2O to identify exchangeable protons. The application of ZnTPP in structural problems involving substituted imidazo[2,1‐b]thiazoles and 2‐benzyl‐1,3‐dioxopyrrolo[3,4‐c]pyridines allows unambiguous identification of the possible structural isomers. To overcome the solvent limitations of ZnTPP, the more soluble Co(III)TPPBr can be used successfully as a shift reagent in DMSO‐d6, CD3OD

ISSN:0030-4921    

DOI:10.1002/omr.1270211009

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe conformational analysis of the diastereomeric 2‐methylsulphinyl‐1‐phenylethanol and itsO‐methyl andO‐acetyl derivatives has been performed by1H NMR spectroscopy. The study of the influence of dilution and solvent polarity changes on the coupling constants has permitted the configurational assignment of each diastereoisomer. The role played by hydrogen bonding in the hydroxysulphoxides has also been studied by IR spe

ISSN:0030-4921    

DOI:10.1002/omr.1270211010

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

ISSN:0030-4921    

DOI:10.1002/omr.1270211001

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY