Photocatalytic three-component radical cascade: a general route to heterocyclic-substituted alkyl sulfones

Abstract

A photoredox-catalyzed three-component radical cascade reaction of β,γ-unsaturated oximes/hydrazones, the sulfur dioxide surrogate of DABCO·(SO₂)₂ and alkenes under mild conditions is developed, affording diverse isoxazoline/dihydropyrazole-substituted aliphatic sulfones in good to excellent yields. This photoinduced radical sulfonylation via the insertion of sulfur dioxide shows good functional group compatibility and excellent regioselectivity. A plausible mechanism is proposed, which involves a radical cascade process with the insertion of sulfur dioxide initiated by an O/N-centered radical from the corresponding β,γ-unsaturated oximes/hydrazones.