From Activation to Assembly: Multifunctional Reagents Enabling Step and Atom Economy in Modern Synthesis

The strategic design of multifunctional reagents has emerged as a powerful paradigm in modern organic synthesis by integrating activation, fragment delivery, and reaction control within a single chemical entity. This review examines advances from 2005 to 2025, highlighting the evolution of multifunctional reagents from classical systems such as DMSO, DMF, dimethyl carbonate, and isocyanides to sophisticated platforms including silylated lactams, vinylene carbonates, aryldiazonium salts, N-alkoxy- and N-alkenoxypyridinium species, bifunctional polymer-supported systems, and inorganic redox mediators. The discussion is organized by reagent architecture and activation mode, covering molecular, heterogeneous, photochemical, and catalyst-programmable systems. Across cascade reactions, multicomponent processes, and late-stage functionalizations, these reagents enable compression of multistep sequences, improved chemoselectivity, and enhanced step and atom economy. Mechanistic insights from kinetic, spectroscopic, isotopic, and computational studies reveal how integrated functionalities such as internal acid or base activation, redox mediation, and proximity effects govern reactivity across radical, ionic, and photochemical pathways. Comparative analysis underscores trade-offs between efficiency, scalability, and cost, while highlighting challenges in reagent synthesis and process translation. Overall, multifunctional reagent design provides a unifying framework for sustainable and efficient molecular construction in both academic and industrial settings.