Rhodium-NHC-Catalyzed gem-Specific O-Selective Hydropyridonation of Terminal Alkynes.

Abstract

The dinuclear complex [Rh(μ‐Cl)(η2‐coe)(IPr)]2 is an efficient catalyst for the O‐selective Markovnikov‐type addition of 2‐pyridones to terminal alkynes. DFT calculations support a hydride‐free pathway entailing intramolecular oxidative protonation of a π‐alkyne by a κ1 N‐hydroxypyridine ligand. Subsequent O‐nucleophilic attack on a metallacyclopropene species affords an O‐alkenyl‐2‐oxypyridine chelate rhodium intermediate as the catalyst resting state. The release of the alkenyl ether is calculated as the rate‐determining step.