Introducing new and effective catalysts for the synthesis of pyridazino[1,2-a]indazole, indazolo[2,1-b]phthalazine and pyrazolo[1,2-b]phthalazine derivatives

In this study, a new and effective catalyst for the synthesis of pyridazino[1,2-a]indazole, indazolo[2,1-b]phthalazine and pyrazolo[1,2-b]phthalazine derivatives was introduced. Triethanolammonium acetate ([TEAH][OAc]) accelerates the reaction in a one-pot and four-component condensation of aldehydes, hydrazine hydrate, succinic/phthalic anhydride, and 1,3-dicarbonyl compounds. The yield of the products is high, and the reaction conditions are mild and solvent-free. Furthermore, the model reaction was conducted in the presence of triethanolammonium sulphate ([TEAH][HSO4] and triethanolammonium formate ([TEAH][HCOO]) under various conditions. In addition, the catalyst is recyclable, therefore, it can be reused several times. The structure of the obtained products was confirmed by comparing the M.P., IR, and H-1 NMR. Advantages of this technique are as following: Synthesis of novel, green, and one-pot and four-component condensation (4CC) under solvent-free conditions at room temperature. The catalytic reaction is performed under mild and environmentally friendly conditions in short reaction times and excellent yields. The catalyst is easily recycled and exhibits good chemical and structural stability. (C) 2020 The Author(s). Published by Elsevier B.V.