An Overview of 3d Metalla-Electrochemical Functionalization for Sustainable Organic Transformations (A Review)

摘要

Abstract To enhance the potency of molecular synthesis, selective oxidative alteration of otherwise inert C–H bonds via transition metal has perceived major attention in the field of coordination chemistry. Academicians wish to capitalize such Csp2–H bond activation/functionalization via cross-coupling such as amination, oxygenation, thiolation, annulation reaction, etc. Despite substantial progress, conventional oxidative C–H activations are generally dominated by precious 4d or 5d transition metal catalysts such as palladium, ruthenium, iridium, and rhodium and less towards economical 3d transition metals such as nickel, cobalt, copper, and manganese. Both approaches compromise the sustainable nature of the C–H activation protocol as it employs the stoichiometric amount of oxidant under a mild condition causing the selective issue of reductive elimination from the metal center and so forth thus forming by-products which is difficult to separate and thus reduce atom economy that limit catalyst turnover that is a major problem in C–H activation step. Favorable sustainability can be procured by the application of electrochemical tools as renewable resources on the stage of C–H activation chemistry catalyzed by transition metals thus, making the procedure environmentally benign. In this scenario, electro-organic mediated functionalization via 3d transition metals is a resource-economical alternative technique that inherits the general idea of economic sustainability due to its inexpensive nature, variable oxidation state, and high chemical reactivity towards various functional groups with unmet site selectivity in an organic molecule. Such electro-organic mediated functionalization via 3d transition metals inspires to develop of selective products via minimization of undesired side reactions which in turn excites the reaction developments on the enhanced energy efficiency of atom economy products with a wide range of functional groups tolerance and thus replacing classical reaction methods and chemical oxidants. This mini-review pays attention to the C–H activation/functionalization of the bond to C–C, C–N, and C–Miscellaneous (P, O, and S) bond linkage by employing different earth-abundant 3d transition metals such as nickel, copper, cobalt and manganese’s using the electrochemical tool until 2023.