Acidic ionic liquids: highly efficient catalysts for one-pot four-component synthesis of pyrazolo [1,2-b] phthalazines under solvent-free conditions

摘要

A series of novel pyrazolo[1,2-b]phthalazine-2-carboxylate derivatives has been synthesized via one-pot four-component reaction of aromatic aldehyde, ethyl or methyl acetoacetate, hydrazine hydrate, and phthalic anhydride in the presence of acidic ionic liquids such as 3-methyl-1-sulfo-1H-imidazol-3-ium chloride, 1,3-disulfo-1H-imidazol-3-ium chloride, and triethyl(sulfo)ammonium chloride as the catalyst. This method involves particular advantages such as environmentally benign catalysts, high yields of product, reusability of ionic liquids with high activity, short reaction times, no hazardous solvent, and easy workup.