One-pot synthesis of multi-substituted conjugated dienones by trapping allene carbocations with active ylides.

A Rh(II)/boron reagent co-catalyzed unprecedent transformation was established for the rapid construction of multi-substituted conjugated dienones under mild conditions by trapping allene carbocations with oxonium ylides from simple starting points in yields up to 85%. Two CC double bonds, one C-C and one C-O single bond were built in this one-pot reaction. The diversity-oriented strategy was also established to synthesize alkyne ether and dihydrofuran derivatives by a substrate-depended fashion.