Borane-Induced Dimerization of Arylallenes.

A series of arylallenes react with HB(C F ) in a 2:1 molar ratio to give the tail-to-tail 1,6-diaryl-2-boryl-hexa-1,5-diene coupling products. The reaction of the phenylallene substrate with HB(C F ) was shown to initially give the 2-boryl-3,4-diphenyl-1,5-hexadiene head-to-head coupling product which then rearranged, by a thermally induced Cope rearrangement, into the final product.