Synthesis of 1,1′-Biindenes and 3,3′-Biindenes

Abstract

1,1′-Biindenes 2, conveniently prepared from indenyllithiums by treatment with copper(II) chloride, are quantitatively isomerized to the corresponding 3,3′-biindenes 3 by heating in triethylamine/pyridine. Both d, l and meso isomers of 2 react to form 3, the rate of reaction of the meso form, however, is substantially faster.