Acyl Isothiocyanates of 2-Allyl- and 2-Benzylmaleopimarimide: Synthesis of 1,3,4-Thiadiazoles

New linear hydrazinocarbonothioyl derivatives of maleopimarimides were synthesized in high yields by the interaction of acyl isothiocyanates of 2-allyl- and 2-benzylmaleopimarimides with acetohydrazide and hydrazide of 4-methoxybenzoic acid. 1,3,4-Thiadiazole derivatives were synthesized by boiling hydrazinocarbonothioyl derivatives of maleopimarimides with a catalytic amount of concentrated H₂SO₄ in ethanol. The structure of the synthesized compounds was determined using ¹H,¹³C NMR, ¹H–¹³C HSQC, ¹H–¹³C HMBC, COSY, NOESY, and ¹H-¹⁵N HMBC spectroscopy methods.