Lewis acid–catalyzed green synthesis and biological studies of pyrrolo[3,4‐c]pyrazoles in aqueous medium

An environmentally benign approach in aqueous medium by means of Lewis acid catalyst affords a wide spectrum of pyrazoline derivatives in satisfactory yields. [3+2] cycloaddition reactions of substituted azomethine‐N‐imines to maleimide in aqueous medium at relatively high concentrations of Lewis acid catalyst have emerged as an environment friendly alternative to conventional solvents. Promising catalytic activity has been revealed by Lewis acid like Cu (NO3)2 in aqueous medium. The obvious features of this synthetic protocol were short reaction time, high efficiency, less hazardous synthesis by benign solvent, catalysis, modest workup, and a clean reaction methodology.