The mixed heterocycles of the type Triazole, Thiadiazole, Oxazoles are very interesting chemical compounds in scientific research because of their potential of application in different fields, for this reason their synthesis has become a very important subject.

Our work aims to synthesize a new series of mixed heterocycles from terephthalic acid, which can be easily converted to monoalkyl terephthalate with good yields, via a two-step procedure. Treatment of monoalkyl terephthalate with SOCl₂ provides methyl terephthalaoyl chloride, which reacts with thiosemicarbazide to give methyl 4-(2-carbamothioylhydrazine-1-carbonyl)benzoate, which is then used to synthesize the 1,2,4-triazole and 1,3,4-thiadiazole heterocycles.