New entry to a cis-fused bicyclic ring system by a [2,3]sigmatropic rearrangement via cyclic allylsulfonium ylides. Synthesis of the cis-2-oxa-9-vinyldecalin skeleton

Abstract

Rhodium(II) acetate-catalysed cyclisation of methyl 2-diazo-5-[2-methoxy-5-(2-phenylsulfanyl-ethylidene)tetrahydro-2H-pyran-4-yl]-3-oxopentanoate 4 proceeded in a stereoselective fashion to provide in a high yield cis-2-oxa-9-vinyldecalin derivative 5, the basic AB ring skeleton of vernolepin, by a [2,3]sigmatropic rearrangement via a nine-membered cyclic allyl sulfonium ylide.