Three‐Component Alkylsulfonylation of 1‐Acryloyl‐2‐Cyanoindoles with Hantzsch Esters through Sulfur Dioxide Insertion

A three‐component alkylsulfonylation/cyclization/hydrolysis relay reaction of 1‐acryloyl‐2‐cyanoindoles with 4‐alkyl Hantzsch esters and Na₂S₂O₅ involving sulfur dioxide insertion has been established to access a series of alkylsulfonyl pyrrolo[1,2‐a]indolediones derivatives. With this method, a variety of primary and secondary alkyl radicals can be used for trapping sulfur dioxide and the corresponding alkylsulfonyl radical intermediates formed in situ, followed by alkyl sulfonyl radical addition, cyclization and hydrolysis. This reaction involves selective cleavage of a carbon‐carbon bond followed by successive formation of three new chemical bonds, in which the cyano group has dual roles as a radical acceptor and a carbonyl source.