Mechanistic Insights Into Catalyst‐Assisted Green Synthetic Approaches Toward Biologically Active 2‐Substituted Benzazoles

ABSTRACT

The development of efficient and environmentally benign synthetic methodologies for biologically active heterocycles remains a central goal in modern organic and medicinal chemistry. Benzazoles, including benzimidazoles, benzoxazoles, and benzothiazoles, constitute an important class of fused heterocycles containing nitrogen, oxygen, and sulfur atoms, with wide‐ranging pharmacological and industrial applications. This review provides a comprehensive overview of recent advances in green synthetic strategies for 2‐substituted benzazoles via condensation of o ‐amino‐, o ‐hydroxy‐, and o ‐mercaptoanilines with non‐aldehyde‐based building blocks, including carboxylic acids and derivatives, orthoesters, primary alcohols, primary amines, aryl/alkyl nitriles, isocyanates, isothiocyanates, β ‐dicarbonyl compounds, carbodiimides, and methyl arenes. Special emphasis is placed on catalyst‐driven transformations involving heterogeneous nanocatalysts, organocatalysts, and recyclable solid‐supported systems under sustainable conditions. Emerging green methodologies, including microwave‐assisted, ultrasound‐assisted, photocatalytic, and electrocatalytic approaches, are also critically discussed. Unlike previous reviews focused mainly on aldehyde‐based routes or individual benzazole subclasses, this work uniquely integrates non‐aldehyde synthetic strategies across all major benzazole frameworks, highlighting catalytic roles, mechanistic insights, and key green chemistry metrics.