Protonation of the reactive intermediates produced in the reaction between alkyl isocyanides and dialkyl acetylenedicarboxylates by 4-methylbenzenesulfonic 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-enedioate derivatives, which react with water to produce dialkyl 2-({alkyl[(4-methylphenyl)sulfonyl]amino}carbonyl)-3-hydroxysuccinates.
alkyl isocyanide - dialkyl acetylenedicarboxylate - 4-methylbenzenesulfonic acid monohydrate - multicomponent reaction
