The conversions of isothiazolium salts into thiophenecarboxylic ester derivatives

Several 3-aminothiophene-2-carboxylic ester derivatives are made by reaction of potassium 3-ethoxy-3-oxopropanoate with isothiazolium salts or by reaction with 2-ethoxy-2-oxoethylidenedimethylsulfurane. In the latter case deaminated products are also isolated. These products are consistent with initial nucleophilic attack on the sulfur atom of the isothiazolium salt. In one case a pyrrole derivative is formed by a novel rearrangement of an intermediate aziridine derivative. Some further derivatives of 3-benzylaminobenzo[b]thiophene are described.