Synthesis and conjugate additions of 2,3,4,9-tetrahydro-1H-xanthene-1,9-diones

Abstract

An efficient two step procedure for the synthesis of 2,3,4,9-tetrahydro-1H-xanthene-1,9-diones is described. A study of their conjugate additions has shown them to be efficient Michael acceptors. Reaction of 2,3,4,9-tetrahydro-1H-xanthene-1,9-dione with tris(methylthio)methyllithium, followed by mercury(II) catalysed methanolysis, gave methyl 1-hydroxy-9-oxo-3,4,4a,9-tetrahydro-2H-xanthene-4a-carboxylate, the nucleus of the secalonic acids and other natural products