V. Vijayabaskar

1H, 13C and 17O NMR study of substituent effects in 4‐substituted phenylthiol esters

The 1H and 13C NMR spectra of 4‐substituted phenylthiol acetates, benzoates and cinnamates and the 17O NMR spectra of a few thiol acetates were measured. The 13C chemical shifts of C‐1 of the thiol esters when correlated with appropriate substituent‐induced chemical shifts (SCS) of monosubstituted benzenes reveal an enhancement of substituent effect at C‐1. Several good dual substituent parameter (DSP) correlations of 13C chemical shifts with σ1 and σR parameters were obtained for the carbons para to the substituent and the carbonyl carbons of all the three series of thiol esters display inverse substituent effects, indicating π‐polarization of the thiol ester functionality by the dipole of the substituent.

Synthesis and multinuclear NMR study of (E)-s-trans -1-acetyl-5-aryl-3-styryl-2-pyrazolines

The reaction of triarylideneacetylacetones with hydrazine hydrate in acetic acid affords an excellent yield of (E)‐s‐trans‐1‐acetyl‐5‐aryl‐3‐styryl‐2‐pyrazolines via decinnamoylation. The structures of these compounds were elucidated using 1H, 13C and two‐dimensional NMR techniques such as H,H‐COSY, C,H‐COSY, NOESY and HMBC. 15N NMR data for these compounds were also obtained and the results are discussed. Copyright

Synthesis and 1H and 13C NMR study of the stereochemistry of (E )‐2‐acetyl‐3‐aryl‐7‐arylidene‐3,3a,4,5,6,7‐hexahydroindazoles

The reaction of 2,6‐diarylidenecyclohexanones with hydrazine hydrate in glacial acetic acid resulted in the formation of diastereomers of (E)‐2‐acetyl‐3‐aryl‐7‐arylidene‐3,3a,4,5,6,7‐hexahydroindazoles. The relative configurations of these diastereomers were unambiguously assigned using 1H and 13C NMR spectroscopic methods.

A proton and carbon NMR spectroscopic study of 5‐substituted acenaphthenes

The proton and carbon NMR spectra of eight 5‐substituted acenaphthenes were obtained. The 13C chemical shifts of C‐6 and C‐2a of these compounds were compared with those of carbons located at structurally similar positions in 1‐substituted naphthalenes (viz. C‐8 and C‐4). The 13C chemical shifts of C‐2a were also analysed using the dual substituent parameter (DSP) equation. The results revealed (i) diminished steric interactions between the 5‐substituent and the adjacent peri‐carbon (C‐6) and (ii) an enhanced transmission of both polar and resonance effects to the carbon para (C‐2a) to the variable substituent, X, in acenaphthenes relative to the corresponding carbons (C‐4) in 1‐substituted naphthalenes. The higher ρI and ρR values observed for C‐2a of acenaphthenes suggest higher polarizability in this system than in naphthalenes. AM1 calculations of charge also showed enhanced substituent effects in the case of most of the substituents in the acenaphthene system.