SYNTHESIS AND APPLICATION OF 5-ARYLAZOTHIOPHENE DERIVATIVES

Synthesis of 5-(hetoarylazo or arylazo)thiophene derivatives (6a-g) was achieved by diazotization of ethyl 5-amino-2,4-bis(ethoxycarbonyl)-3-thiopheneacetate (3) using nitrosyl hydrogensulfate, coupling with suitable heterocyclic hydroxy and N,N-dialkyl-substituted arylamines which resulted in thiophene azo dyes. The key intermediate 3, used as the diazonium component, was synthesized in one pot and in excellent yield from diethyl 3-oxopentanedioate, sulfur and ethyl cyanoacetate following the Gewald Synthesis. The dyes when applied as disperse dyes on polyester fibres gave excellent results.