Application of Ynamides in the Synthesis of 2-(Tosylamido)- and 2,5-Bis(tosylamido)thiophenes

Abstract

A step-economic and metal-catalyst-free synthesis of 2-(tosylamido)- and 2,5-bis(tosylamido)-thiophenes from nonsymmetrical 1,3-butadiynamides and symmetrical 1,3-butadiyne-1,4-diamides is reported. The reaction proceeds in the presence of Na2S·9H2O (2-3 equiv) under mild reaction conditions (50 °C) and is facilitated by polarized carbon-carbon triple bonds in ynamides. This new approach to thiophenes based on the chemistry of ynamides was applied to the synthesis of a bis(tosylamido)-capped terthiophene having a string of N,S-heteroatoms embedded in a highly π-conjugated molecular frame.