Steroids and steroid analogues from Stille-Heck coupling sequences

Abstract

Tricyclic 1,3,5-hexatrienes were prepared from 4-substituted 2-bromocyclohexenyl triflate, enantiomerically pure hexahydroindenylstannanes, and tert-butyl acrylate in a sequence of Stille and Heck reactions. In the example shown, an enantiomerically pure steroid with protected functionalities in the 3-, 7-, and 17-positions is formed in a 6π-electrocyclization upon heating at 220°C.