Reactions of geranyl and farnesyl halide, and their geometricalisomers with chlorotris(triphenylphosphine)cobalt(I) gave the corresponding geometrically pure coupling products under mild and non-basic conditions. Squalenes were stereospecifically synthesized by this method.
The RuO4-catalyzed oxidative polycyclization of digeranyl, a Cs-symmetric tetraene possessing a repetitive 1,5-diene structural motif, has been studied. The required substrate has been synthesized by Ti(III)-mediated tail-to-tail homocoupling of geranyl bromide. The process afforded two hitherto unknown isomeric tris-tetrahydrofuran products possessing unexpected all-threo cis–trans–cis and cis–trans–trans