One-Pot Synthesis and Functionalization of Polyynes via Alkylidene Carbenoids

A one-pot, two-step method for the synthesis of diynes and triynes is reported. The reaction of a dibromoolefinic precursor with BuLi effects a Fritsch-Buttenberg-Wiechell rearrangement and generates a lithium acetylide intermediate, which is then trapped with a variety of electrophiles to produce substituted diynes and triynes. Alternatively, transmetalation from the lithium acetylide to give a zinc acetylide provides a nucleophilic coupling partner for aryl iodides in the presence of palladium to form symmetrical or unsymmetrical diynes and triynes via the Negishi coupling.