Elimination–addition. Part XXII. Addition of enolates to allenic sulphonium salts; a new general furan synthesis

Abstract

Furans are produced by reactions of β-keto-esters, β-diketones, and β-keto-sulphones with allenic sulphonium salts. Procedures are simple and yields are high. 2,3,4-Trisubstituted furans are typically produced by this method, which thus complements synthesis of 2,3,5-trisubstituted furans from prop-2-ynyl halides and β-keto-esters. Mechanistic aspects of the synthesis are briefly discussed.