Carbofunctionalization of Terminal Alkynes via Rhodium Catalysis Enabling Formations of Four Different Bonds

Described here is the oxygenative carbofunctionalization of terminal alkynes mediated by combined rhodium catalysis that enables regioselective quadruple formation of C-C, C-H, C-O, and C-heteroatom bonds. Mechanistic studies suggest that a disubstituted rhodium vinylidene complex is generated upon C-C bond formation at the terminal alkyne with tethered electrophiles such as alkyl halides, aldehydes, imines, and Michael acceptors. Subsequent intermolecular transfer oxygenation of the rhodium vinylidene with pyridine N-oxide generates a rhodium-complexed ketene intermediate that reacts with a variety of heteroatom nucleophiles to give rise to cyclic carboxylic acid derivatives.