A Novel Synthesis of Allenic Lactones by Use of the [2,3]Sigmatropic Rearrangement of Cyclic Propargylsulfonium Ylides

Abstract The [2,3]sigmatropic rearrangement of the cyclic propargylsulfonium ylides generated from ethyl 5-phenylthio-3-pentynyl and ethyl 6-phenylthio-4-hexynyl diazomalonates provided the novel allenic lactones, 2-ethoxycarbonyl-2-phenylthio-3-vinylidene-5-pentanolide and 6-hexanolide, respectively.