Palladium-Catalyzed Decarboxylative Coupling of Alkynyl Carboxylic Acids and Alkenyl Tosylates for the Synthesis of Enynones.

A palladium-catalyzed decarboxylative coupling reaction was developed for the synthesis of 3-(1-alkynyl)-2-cyclohexen-1-ones. A variety of alkynyl carboxylic acids were coupled with 3-oxocyclohexenyl tosylates to afford the corresponding enynones in good to excellent yields. The developed catalytic system is phosphine free and showed good tolerance toward various functionalities such as chloride, cyano, nitro, ester, aldehyde, and alcohol groups. In addition, phenylpropiolic acid exhibited higher reactivity in the reaction with alkenyl toslyate than phenyl acetylene.