Arylsulfonylpyrroles from Reaction of Tosylmethyl Isocyanide (TOSMIC) with 3-Arylsulfonyl Acrylates as Michael Acceptors

Abstract

Ethyl 3-(arylthio)acrylates did not react with α-alkali metalated tosylmethyl isocyanide (TosMIC) to afford 4-(arylthio)pyrrole-3-carboxylic acid ethyl esters. Oxidation of thioethers to sulfones generated reactive 3-(arylsulfonyl) acrylates, which promptly underwent cycloaddition with TosMIC in the presence of base giving ethyl 4-(arylsulfonyl)pyrrole-3-carboxylates. Contrary to expectation, the use of ethyl 3-(5-chloro-2-nitrophenylsulfonyl)acrylate led to ethyl ester of 5-tosylpyrrole-3-carboxylic acid instead of the expected ethyl 4-(5-chloro-2-nitrophenylsulfonyl)pyrrole-3-carboxylate.