Robust Cobalt(II)Porphyrin Catalyzed Stereo‐Divergent Coupling of Phosphorous Ylides

Comprehensive Summary A visible‐light‐driven, cobalt(II) porphyrin‐catalyzed aerobic oxidative coupling of phosphorus ylides to 1,4‐enediones is reported. This photocatalytic system is highlighted by its exceptionally low catalyst loading (2.5 × 10 −3 mol%) and short reaction time, achieving a turnover number (TON) of up to 19800 and a turnover frequency (TOF) of up to 39600 h −1 —values rarely attained in photocatalytic transformations. Moreover, the stereoselectivity of this reaction can be precisely modulated by varying the irradiation wavelength. A broad substrate scope, including various heterocycles such as indoles, thiophenes, and thiazoles, is well tolerated. Mechanistic studies reveal the involvement of singlet oxygen ( 1 O 2 ) and superoxide anion (O 2 •‐ ), and a sequential pathway involving the oxidation of the phosphorus ylide to 2‐oxo‐2‐arylacetaldehyde, and followed by a Wittig reaction. Besides, a blue LED‐triggered isomerization of ( E )‐1,4‐enediones is responsible for ( Z )‐products formation. This work demonstrates the potential of metalloporphyrin as highly efficient and robust photocatalysts for organic synthesis.