Transition-metal-catalyzed regioselective CN bond formation of benzotriazoles

Benzotriazoles are privileged heterocyclic scaffolds with broad applications across pharmaceutical, agrochemical, and materials sciences. However, regioselective N-functionalization remains a persistent challenge due to the inherent tautomeric equilibrium between the 1H- and 2H-forms. Because classical electrophilic substitutions often favor N 1 -substituted products, selective access to the synthetically and biologically valuable N 2 -functionalized benzotriazoles remains comparatively challenging. Over the period from 2009 to 2026, transition-metal catalysis, together with selected Lewis-acid-mediated strategies, has emerged as a powerful approach to override intrinsic substrate preferences and enable catalyst-controlled access to both N 1 - and N 2 -functionalized benzotriazoles. This review provides a comprehensive overview of recent advances in transition-metal-catalyzed regioselective C N bond formation of preformed benzotriazole frameworks, together with selected Lewis-acid-mediated systems that provide mechanistic insight into N 1 /N 2 control. We systematically discuss diverse reaction manifolds, encompassing transformations with alkenes and alkynes, cross-coupling with (hetero)aryl electrophiles, reactions with alcohols, Michael-type additions to activated alkenes, carbene-transfer reactions, and other C(sp 3 )–N bond-forming reactions. Particular emphasis is placed on how coordination environments, through the combined effects of metal identity, ligand architecture, additives, and reaction parameters, control or switch N 1 /N 2 selectivity. In selected systems, these factors also determine whether the product distribution is controlled by kinetic product formation or by subsequent equilibration. By summarizing the underlying mechanistic pathways, transition-state models, and the experimental and computational evidence supporting them, this review provides a mechanistically grounded framework for the rational design of regioselective functionalizations. Finally, remaining challenges and future opportunities, including asymmetric N 2 -functionalization, the utilization of earth-abundant metals, green synthetic methodologies, and machine learning-guided data-driven discovery, are outlined to further expand the potential of these vital heterocycles.