Bromination of Substituted Pyrazolo[4,3-c]pyrazoles

Pyrazoles and their fused derivatives are very versatile and widely applicable in various industries, including chemical, pharmaceutical, and agricultural. Pyrazolo[4,3-c]pyrazoles are insufficiently represented in the literature class of fused heterocyclic compounds. They have already been described as promising high-energy materials, yet their biological activities have received little investigation. The work focused on the bromination of pyrazolo[4,3-c]pyrazoles, which contain functional groups important in biologically active molecules and can be further modified. We have performed the bromination of pyrazolo[4,3-c]pyrazoles for the first time. The bromination of 1,3-dimethyl-1,4-dihydropyrazolo[4,3-c]pyrazole using various reagents was performed. Even when different bromination agents were used, the target product yield was high in all cases. It has been established that the best results for halogenation were achieved with bromine in acetic acid in the presence of sodium acetate. The bromination of other pyrazolo[4,3-c]pyrazole derivatives was carried out under these conditions. These reaction conditions provided high yields of the target products and were tolerant to some functional fragments of the molecules.