On the coupling of aryldiazonium salts with N,N-disubstituted 2-aminothiophenes and some of their carbocyclic and heterocyclic analogues

Abstract

As exemplified with the morpholino derivatives 7, N,N-disubstituted 2-aminothiophenes couple, depending on the substitution pattern at C(5), with aryldiazonium salts 1 either at their C(3) or C(5) position yielding the corresponding 3-arylazo-2-morpholinothiophenes 9 or, under elimination of the substituent at C(5), 5-arylazo-2-morpholinothiophenes 10. This reaction contrasts to the behaviour of 5-morpholinothiazoles 8 and dimethylaniline 13 towards the same diazonium salts 1 which are unable to couple with these compounds if their C(5) or C(4) position, respectively, is not substituted by H, COOH or CHO.