Synthesis of functionalized sulfonamides via multicomponent reaction of alkyl isocyanide and dialkyl acetylenedicarboxylate with 4-methylbenzenesulfonic acid monohydrate

Protonation of the reactive intermediates produced in the reaction between alkyl isocyanides and dialkyl acetylenedicarboxylates by 4-methyl benzenesulfonic acid monohydrate leads to vinylnitrilium cations, which undergo a nucleophilic reaction with the conjugate base of the 4-methylbenzenesulfonic acid to produce dialkyl (E)-2-(alkylimino) {(4-methylphenyl)sulfonyl]oxy}methyl)but-2-enedioates. These intermediates rearrange to dialkyl (E)2-({alkyl)[(4-methylphenyl)sulfonyl]amino}carbonyl)but-2-enedi- oate derivatives, which react with water to produce dialkyl 2(lalkyl[(4-methylphenyl)sulfonyl]aminolcarbonyl)-3-hydroxysuccinates.