Efficient assembly of α-methylene-γ-butyrolactones via a novel, tandem Claisen-ene rearrangement

A novel method for the rapid assembly of α-methylene-γ-butyrolactones, using a tandem Claisen-ene rearrangement as a key step, is presented. The importance of the structure of the Lewis acid promoters and the mechanism of action of Et2AlSPh are discussed.