Hydroaminocarbonylation of Alkynes to Produce Primary α,β-Unsaturated Amides Using NH₄HCO₃ Dually as Ammonia Surrogate and Brønsted Acid Additive

By using NH₄HCO₃ dually as ammonia surrogate and Brønsted acid additive, the production of primary α,β-unsaturated amides via hydroaminocarbonylation of alkynes was accomplished efficiently. The advantages of using the solid and inexpensive NH₄HCO₃ included: (1) the facile and clean manipulation without presence of stinky gaseous NH₃ or liquids organic amines, (2) the inhibition of the subsequent dehydration and hydrolysis of amides due to its weak basicity, and (3) the facilitated formation of Pd−H catalytic active species by the released H₂CO₃ serving as a weak Brønsted acid additive. In addition, the diphopshine of Dppp with the natural bite angle (β_n) of 91° was found indispensable to spur the performance of the palladium catalyst for this reaction. Both terminal and internal phenylacetylene derivatives could be used as the substrates, affording the corresponding primary α,β-unsaturated amides in good yields along with excellent regio-selectivities to the branched ones.