Photocatalytic Regioselective [2 + 2 + 1] Radical Annulation of Alkenes with tert -Butyl Nitrite and gem -Dihalides.

A visible-light photocatalytic regioselective [2 + 2 + 1] radical annulation reaction of alkenes, tert -butyl nitrite, and gem -dihalides has been developed. The protocol provides an efficient and practical approach to obtain isoxazolines in good yields under mild conditions. Significantly, gem -dihalides serve as C1 synthons, while cheap tert -butyl nitrite acts as an ideal "N-O" synthon.