Palladium-Catalyzed Intermolecular Addition of Formamides to Alkynes

A novel palladium system for an intermolecular addition of formamides to alkynes has been developed. The reaction of formamides with internal alkynes in the presence of a palladium catalyst with acid chloride as an additive afforded (E)-alpha,beta-unsaturated amides regio- and stereoselectively. The same catalyst system realized the first example of the addition of formamides to terminal alkynes giving the corresponding alpha,beta-unsaturated amides bearing a terminal methylene moiety as major products. The present reaction was widely applicable to substrates with various functionalities. This method also could be applied to the reaction of N,N-disubstituted formamides with norbornene. A hydridopalladium species would be formed as a key intermediate with in situ generated HCl under the reaction conditions.