Efficient Synthesis of an Enantiopure Thiasteroid by a Double Heck Reaction

Abstract

The thiaestrane 7 was synthesized by two sequential Heck reactions starting from the thiophene derivatives 8a–8c, which contain a ( Z )-halogenovinyl group, and the enantiopure hydrindene 2a. The first intermolecular Pd-catalyzed reaction leads to 11a and 11b in a highly regio- and diastereoselective manner. A subsequent intramolecular Heck reaction catalyzed by the palladacycle 4 then gave the thiasteroid 7 with an unusual cis -junction of the rings B and C.