starting from readily available 2-substituted-4-methylthiazole-5-carboxylic acid hydrazide (1), the title compounds were prepared. the reaction of compound 1 (r=ch3) with formic acid yielded 1-(formyl)-2-(2,4-dimethylthiazole-5-carboxyl) hydrazine (2). refluxing the latter with phosphorous pentasulfide in xylene afforded compound 3, the reaction of compound 2 with phosphorous pentoxide afforded...
