Visible light-mediated gold-catalyzed alkynylative cyclization of allenoates with iodoalkynes for the synthesis of β-alkynyl-γ-butenolides
A method for the tandem cyclization/alkynylation of allenoates with iodoalkynes via gold catalysis under light irradiation is described. This transformation features a broad substrate scope, good functional group tolerance, and compatibility with heterocyclic substrates. The reaction proceeds smoothly at room temperature by using cheap, readily available acriflavine (ACF) as a photocatalyst, and offers β-alkynyl-γ-butenolides derivatives in moderate to good yields. Initial mechanistic studies suggest that a vinylgold(I) complex acts as a key intermediate, which would undergo photosensitization from the ACF singlet excited state. The corresponding energy transfer would promote the oxidative addition of the iodoalkyne partner to deliver C(sp2)–C(sp) coupling products after reductive elimination.
Yuanhao He, Yu Zhong, Maria Ballarin Marion, Jorge C. Herrera Luna, Wanping Ma, Yanfei Hu, Cyril Ollivier, Virginie Mouriès-Mansuy, Louis Fensterbank, Fen Zhao,* Zhonghua Xia* and Baomin Fan
Org. Chem. Front., 2024,11, 5695-5702