The reactions of lead tetra-acetate with substituted benzothiazolylhydrazones

Abstract

In the reaction of benzothiazolylhydrazones of some aromatic aldehydes with lead tetra-acetate the presence of a sulphur atom in the potential cyclisation site of the heteroaryl moiety inhibits the cyclisation reaction. Thus, the reaction of substituted benzothiazolylhydrazones involves an acetoxylation of the hydrazone and not a cyclisation reaction as had previously been reported. Cyclisation of the hydrazone to a triazolobenzothiazole moiety does, however, occur as a minor competitive process. A convenient route for converting the acetoxylated products to cyclised triazolobenzothiazoles has been developed thereby overcoming the most serious limitation in the use of the lead tetra-acetate–hydrazone reaction in the benzothiazole series.