Site‐Selective γ‐Trihalomethylation and γ‐Dihalomethylidenation of Silyl Dienol Ethers under Organophotoredox Catalysis
Résumé
Abstract We report a general remote tribromo‐ and trichloromethylation process using CBr 4 and CBrCl 3 as ready available sources of trihalomethyl radicals. This method operates under mild and metal‐free photocatalyzed conditions and enables the access to γ‐trihalomethylated enals with complete regioselectivity in up to 71 % isolated yield. Importantly, this protocol is easily adapted to the selective one‐pot synthesis of the corresponding γ‐dihalomethylidenated enals in up to 49 % overall yield. Mechanistic studies are in favor of a radical chain propagation initiated by an oxidative quenching of the photocatalyst.