Tandem Gold Self‐Relay Catalysis for the Synthesis of 2,3‐Dihydropyridin‐4(1 H)‐ones: Combination of σ and π Lewis Acid Properties of Gold Salts

The dual ability of gold salts to act as π‐ and σ Lewis acids has been exploited in a tandem self‐relay catalysis. Thus, triphenylphosphanegold(I) triflate mediated the intramolecular carbonyl addition of the amide functionality of homoprogargyl amides to a triple bond. The formation of a σ complex of the gold salt with the intermediate oxazine promoted a nucleophilic addition followed by a Petasis–Ferrier rearrangement. This tandem protocol, catalyzed by the same gold salt under the same reaction conditions, gave rise to the efficient synthesis of 2,3‐dihydropyridin‐4‐(1 H)‐ones, which contain a cyclic quaternary α‐amino acid unit. The asymmetric version was performed by generating the starting materials from the corresponding sulfinylimines.