2-(Methoxycarbonyl)thiophen-3-yl-diazonium Salts: Efficient Precursors for the Formation of C–C Bonds in Thiophene-Containing Heterocyclic Systems

A first application of 2-(methoxycarbonyl)thiophen-3-diazonium salts in the halothienylation of α,β-unsaturated functionalized compounds under Meerwein reaction conditions is presented. This process provides thiophene-containing building blocks that can then undergo cyclization reactions with bisnucleophiles to synthesize thiophene-3-yl-containing heterocyclic systems. In this way, substituted 2,3'-bithiophene compounds and thiophene-3-yl derivatives of 2-aminothiazole, 2-aminoselenazole, thiazolidine, and selenazolidine can be efficiently prepared.