An Overview on the Catalytic Strategies for the Synthesis of Benzodiazines.

In recent decades, N-heterocycles have emerged as a crucial class of organic compounds with wide-ranging applications in pharmaceuticals and agrochemicals. Among them, benzodiazines, containing a benzene ring fused with a six-membered diazine containing both nitrogen atoms in the same ring, are of particular significance. Their structural compactness, synthetic versatility, and favorable physicochemical characteristics render them valuable as drug candidates, chemical probes, and intermediates in organic synthesis. Representative members of this class are cinnoline, phthalazine, quinazoline, and quinoxaline that exhibit numerous pharmacological properties, namely anticancer, antimicrobial, anti-inflammatory, anticonvulsant, antimalarial, antioxidant, antihypertensive, and other activities. Although the synthesis of each scaffold has been reviewed individually in the literature, benzodiazines as a broader class remain comparatively underexplored. The present work summarizes recent developments in the synthesis of benzodiazines, with emphasis on methodologies utilizing diverse catalysts such as solid acid catalysts, nanocatalysts, transition-metal catalysts, and ionic liquid-based catalysts. These strategies commonly employ precursors including 2-nitrobenzyl alcohols, 2-alkynylanilines, o-phenylenediamines, and o-alkyl benzophenones, which react with benzylamines, nitrosoarenes, 1,2-dicarbonyls, and di-tert-butyl azodicarboxylate, respectively. This overview aims to stimulate further exploration in the synthesis and applications of benzodiazines.