Functionalization of 2-Phenylsulfonyl 1,3-Dienes via Cyclopropanation and Epoxidation. Synthesis of Oxabicyclic Systems via BF3-Induced Rearrangement of Epoxide Derivatives

Article abstract of DOI:10.1021/jo00117a006

Regioselective cyclopropanation and epoxidation of 2-phenylsulfonyl 1,3-dienes using dimethyloxosulfonium methylide ((CH3)2SOCH2) and m-chloroperbenzoic acid (m-CPBA) gave access to 3,4-epoxy-1,2-methylene-2-phenylsulfonyl alkenes.The Lewis acid-catalyzed rearrangement of these substrates using BF3*OEt2 or LiClO4 was studied.The outcome of the rearrangement appeared to be very much dependent on substrate stereochemistry and substitution pattern, since both ketones and bicyclic ethers (the oxo analogue of the tropa alkaloid skeleton) were isolated.Further functionalization of one of the bicyclic ethers (3-(phenylsulfonyl)-8-oxabicyclo<3.2.1>-2-octene) was undertaken, proceeding with excellent stereoselectivity in all the cases investigated.This opens a way for synthesis of cis-2,5-disubstituted tetrahydrofurans.