Design, synthesis and insecticidal activity of new 1,3,4-thiadiazole and 1,3,4-thiadiazolo[3,2-a]pyrimidine derivatives under solvent-free conditions

5-(3-Chlorophenyl)-1,3,4-thiadiazol-2-amine 2 was synthesized and employed to synthesize new 1,3,4-thiadiazole and 1,3,4-thiadiazolo[3,2-a]pyrimidine derivatives via reactions with variant electrophilic reagents under solvent-free conditions. The chemical structures of these novel compounds were elucidated scrupulously by aiding elemental data and spectroscopic techniques. The synthesized compounds were evaluated for the insecticidal activity against cotton leaf worm (Spodoptera littoralis). It was realized that the insecticidal activity of 1,3,4-thiadiazolo[3,2-a]pyrimidine derivatives emerged remarkable results comparable with 1,3,4-thiadiazole derivatives against cotton leafworm (Spodoptera littoralis).