Gold catalysed Cyclisation of tert-Butyl Allenoate: General Entry into 2,4-Functionalised Butenolides

Abstract

AuCl3 efficiently catalyzes cylcization of tert-butyl allenoates into gamma-butenolides. Advantage of directly using allenic ester precursor instead of corresponding acid is demonstrated in the synthesis of a variety of 2,4-disubstituted butenolides. A low catalyst loading and mild reaction condition makes this process an attractive alternative over conventional methods using strong Lewis acids.