An I₂-Catalyzed, Visible-Light Photoredox-Mediated Radical Conversion of α-Nitrocarbonyls to Nitrile Oxides: Catalytic Access to Isoxazolines and Isoxazoles from Alkenes and Alkynes

A visible light-mediated, I₂-catalyzed intermolecular transformation of alkenes, conjugated dienes, styrenes, and alkynes to isoxazolines and isoxazoles with α-nitrocarbonyls is reported. The reaction is also applicable to 1,1-disubstituted terminal, 1,2-disubstituted internal and trisubstituted alkenes, and tolerates various functional groups including epoxides, heterocycles, phosphates, alcohols, and thiocyanates. Mechanistic studies reveal that α-nitrocarbonyls are first converted to α-carbonyl radicals followed by their conversion to acyl nitrile oxides, which subsequently undergo [3 + 2] dipolar cycloaddition reactions with the unsaturated molecules.