Preparation, Crystal Structures, and Spectroscopic and Chemical Properties of 2,4,6-Trifluorophenyl- or 4-(Methoxycarbonyl)phenyl-Substituted (E)-1-(3-Guaiazulenyl)ethylene and (2E,4E)-1-(3-Guaiazulenyl)-1,3-butadiene Derivatives

Abstract

Abstract Wittig reactions in general provide a mixture of E and Z geometric isomers, while reactions of 2,4,6-trifluorobenzaldehyde [and (E)-3-(2,4,6-trifluorophenyl)propanal] with the Wittig reagent (3-guaiazulenyl)triphenylphosphonium bromide in ethanol containing NaOEt at 25 °C for 24 h under argon give only new E (and 2E,4E)-forms selectively, i.e., (E)-1-(3-guaiazulenyl)-2-(2,4,6-trifluorophenyl)ethylene and (2E,4E)-1-(3-guaiazulenyl)-4-(2,4,6-trifluorophenyl)-1,3-butadiene. For comparative purposes, Wittig reactions of methyl 4-formylbenzoate, 4-(dimethylamino)benzaldehyde, methyl 4-[(E)-2-formylethenyl]benzoate, and (E)-3-[4-(dimethylamino)phenyl]propanal: namely, possessing an electron-withdrawing (–COOCH3) {or an electron-donating [–N(CH3)2]} group at the C-4 position of the benzene ring, with (3-guaiazulenyl)triphenylphosphonium bromide in methanol (or ethanol) containing NaOMe (or NaOEt) at 25 °C for 24 h under argon afford a mixture of the corresponding geometric isomers respectively. Along with spectroscopic properties and crystal structures of the isolated products, the chemical behavior of those products toward 1,1,2,2-tetracyanoethylene (TCNE) in benzene at 25 °C for 24 h under argon is reported with a view to comparative study.