Carbon-carbon bond forming reactions of acetylenic esters and ketones within frustrated phosphane/borane Lewis pair frameworks.

The three-component reactions of bulky diarylbutenylphosphanes with dimethyl acetylenedicarboxylate (1a) and the strong boron Lewis acid B(C6F5)3 give the ylide-substituted cyclopropane derivatives 26. The acetylenic ester 1a and ketone 1b react with oligomethylene bridged frustrated phosphane/borane Lewis pairs to give the bicyclic C-H insertion/C-C coupling reaction products. The formal carbene products are formed by means of stepwise sequences involving polar intermediate.