A Two-Step Preparation of α-Alkylidene γ-Lactones from γ-Lactones: A Synthesis of (+/-)-Ancepsenolide

Article abstract of DOI:10.1021/jo00225a052

γ-Butyrolactone, γ-valerolactone, and the cis lactone of 2-hydroxycyclohexaneacetic acid have been C-silylated via their respective lithium enolates with diphenylmethylchlorosilane.The resulting α-silylated γ-lactones can be deprotonated and condensed with aldehydes and ketones to give α-alkylidene γ-lactones in moderate to excellent yield.The enolate of the α-diphenylmethylsilyl cis lactone of 2-hydroxycyclohexaneacetic acid condensed with 1-butanal but not with benzaldehyde or acetaldehyde.