One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

摘要

Herein, we describe a novel approach for the practical synthesis of tetrasubstituted thiophenes 8 . The developed method was particularly used for the facile preparation of thienyl heterocycles 8 . The mechanism for this reaction is based on the formation of a sulfur ylide-like intermediate. It was clearly suggested by (i) the intramolecular cyclization of ketene N,S -acetals 7 to the corresponding thiophenes 8 , (ii) 1H NMR studies of Meldrum’s acid-substituted aminothioacetals 9 , and (iii) substitution studies of the methoxy group on Meldrum’s acid containing N,S -acetals 9b . Notably, in terms of structural effects on the reactivity and stability of sulfur ylide-like intermediates, 2-pyridyl substituted compound 7a exhibited superior properties over those of others.