Electrophilic substitution of β,γ-unsaturated esters and ketones using phenyl vinyl sulphoxide as a vinyl cation synthon

Abstract

This paper describes a number of examples in which phenyl vinyl sulphoxide is used as a vinyl cation equivalent to react with sterically hindered, charge-stabilized anions derived from α-alkyl-β,γ-unsaturated ketones and esters. With the β,γ-enones (4), (7), and (22), the Michael addition proved to proceed effectively upon using a catalytic amount of base and t-butyl alcohol as solvent. Pyrolysis of the addition product and subsequent distillation in vacua afforded the β,γ;β′,γ′-dienones in good yields. The α,β-enone (1) and the β,γ-unsaturated esters (10) and (15) reactions were performed using sodium hydride as base in benzene. Pyrolysis of the Michael addition products (2), (11), and (16) yielded the β,γ;β′,γ′-dienone (3) and the β,γ;β′,γ′-unsaturated esters (12) and (17). The β,γ;β′,γ′-dienones (13), (14), (18), and (19) have been obtained by subsequent saponification of the two esters, conversion of the resulting carboxylic acids into the corresponding acyl chlorides, and reaction of the latter with dimethyl- or diphenyl-cuprate.