Preparation of 3-cyano-4-(R-vinyl)-5,5-dimethyl-Δ3-butenolides and substituent effects on their infrared spectra

Abstract

Twenty nine 3-cyano-4-(R-vinyl)-5,5-dimethyl-Δ3-butenolides were prepared by condensation of 3-cyano-4,5,5-trimethyl-Δ3-butenolide with aliphatic and aromatic aldehydes. The wave numbers of C=O, C=N and C=C stretching vibrations of synthesized compounds were measured in trichloro- and tetrachloromethane. The spectral data were correlated with substituent conotants using Hammett-Brown and the improved and extended Seth-Paul-Van Duyse equation. The statistical results of correlations were compared with those of ethyl α-cyanocinnamates, ethyl benzoates and benzonitriles. The transmission factors for one and two C=C bonds were determined in the regions of π' = 0.46-0.57 and 0.27-0.37, respectively. In 3-cyano-4-(arylvinyl)-5,5-dimethyl-Δ3-butenolides a considerable conjugation exists between the arylvinyl moiety and both the C=O and C=N groups. On the other hand, in 3-cyano-4-(alkylvinyl)-5,5-dimethyl-Δ3-butenolides probably only the endocyclic C=C bond takes part in a marked resonance interaction with alkylvinyl group. A generally valid relationship was found between the slopes of ν(C=O) vs σ+ and ν(C=N) vs σ+ correlations for different types of compounds measured in CHCl3 and CCl4.