Bromolactonisations and syntheses towards cyclitols

Abstract

A convenient, high yielding synthesis of bromolactones from unsaturated carboxylic acids has been achieved employing bromine and thallous carbonate. Several methods of bromolactonisation have been compared for a series of substrates. In general the new method affords a higher yield of the bromolactone. Various strategies to effect singlet oxygen addition to isoprene have been investigated. A new route to the stereoisomers of 1,4-diacetoxy-2-methyl-1,3-butadiene has been developed resulting in an improved yield. The Diels-Alder reactions of these isomers and 1,2-diphenylsulfonylethylene were unsuccessful.