Synthesis and Reactivity of Vinyl Quinone Methides

Article abstract of DOI:10.1021/jo00207a006

Vinyl quinone methides 4a and 4b were obtained in high yields by Ag2O oxidation of eugenol (3a) and of 2,6-dimethoxy-4-(2-propenyl)phenol (3b).Vinyl quinone methides (VQMs) reacted with alcohols, with phenols, and with acetic acid giving compounds 5 and 6.As the former rearranged to the latter in the reaction medium, the addition of the reported substrates to VQMs turned out to be wholly regioselective toward the formation of coniferyl and sinapyl derivatives 6.In contrast, addition of carbon nucleophiles (acetylacetone and EtNO2) to VQMs gave both compounds 7 and 8.By reaction of the acetates 6a and 6b (CR=CH3CO) with LiAlH4 it was possible to perform a novel synthesis of coniferyl and sinapyl alcohols (1a and 1b).Treatment of the same acetates with an aqueous solution of NaHCO3 reproduced VQMs 4, which by subsequent reduction with NaBH4, gave propenylphenols 2 and allylphenols 3.Formation of the latter compounds from coniferyl and sinapyl acetates via VQM is here proposed as a possible biosynthetic pathway.