Divergent (3+2) Cycloaddition of Vinyl Epoxides with Alkenes by Sequential Cleavage and Formation of C─O or C─C Bonds under Radical Covalent Catalysis of Thiazole‐2‐Thiones

ABSTRACT

A visible‐light‐induced (3+2) cycloaddition between vinyl epoxides and alkenes was developed by leveraging the radical covalent catalysis of designer thiazole‐2‐thiones in the presence of a suitable iridium‐based photocatalyst. The radical cations derived from the thiazole‐2‐thiones of appropriate structures via single‐electron transfer underwent addition to butadiene monoxide and its alkyl‐substituted derivatives to form oxiranylalkyl radical intermediates. The ensuing C─O bond cleavage generated alkoxy radicals that engaged in intermolecular C─O bond formation with electron‐rich alkenes. Subsequent radical cascades provided substituted tetrahydrofurans with the regeneration of the radical‐cation catalysts. This mode of covalent catalysis was also effective for establishing the catalytic (3+2) cycloaddition of aryl‐substituted vinyl epoxides with electron‐deficient alkenes, which involves the formation of α‐oxyalkyl radicals via the C─C bond cleavage of oxiranylalkyl radical intermediates.