Unexpected products from the reaction of different compounds with hydrazine hydrate or aryl thiosemicarbazides

Abstract The reaction of 2,5-dihydroxyacetophenone I or 1-(1,4-dihydroxynaphthalen-2-yl)ethanone II with various 4-aryl thiosemicarbazides did not yield the expected 4-aryl-1-[1-(2,5-dihydroxyphenyl)ethylidene]thiosemicarbazides III nor 4-aryl-1-[1-(1,4-dihydroxy-naphthalen-2-yl)ethylidene]thiosemicarbazides IV , respectively. However, unexpected products were formed namely, N 1 , N 2 -bis[1-(2,5-dihydroxyphenyl)ethylidene]hydrazine V or N 1 , N 2 -bis[1-(1,4-dihydroxynaphthalen-2-yl)ethylidene]hydrazine VI , respectively. Also, an unexpected product N 1 , N 2 -bis(2,5-dimethoxybenzylidene)hydrazine XI was obtained when heating under reflux diethyl 2-(2,5-dimethoxybenzylidene)propanedioate VII or ethyl 2-cyano-3-(2,5-dimethoxyphenyl)propenoate VIII with 99% hydrazine hydrate in ethanol. The mechanisms of these reactions were proposed.