AIBN-Mediated Radical Cascade Synthesis of Maleimide-Fused Thiochromenes

A radical cascade reaction has been established for the efficient synthesis of an entirely new class of heterocycles, i.e., maleimides-fused thiochromenes. The cascade reaction between aryl thiols and styryl diazo imides is initiated by a radical initiator, i.e., AIBN, to generate thiyl radical, which undergoes a chemoselective intermolecular addition to the C═C bond to generate other radical species, which further cyclize with the liberation of dinitrogen. The synthetic approach allows rapid access to the diverse thiochromenes in good yields under mild reaction conditions.