chemoreduction

Chemo- reduction is the chemical reduction of a substrate by reagents that donate electrons or hydrogen equivalents in a purely chemical process, as opposed to electrochemical or photochemical methods. It encompasses a range of strategies that convert oxidized functionalities into reduced products through direct chemical reagents.

Common reductants used in chemoreduction include hydride donors such as sodium borohydride (NaBH4) and lithium aluminum hydride (LiAlH4), as well as more specialized reagents like diisobutylaluminum hydride (DIBAL-H) and borane complexes. Catalytic hydrogenation, which uses molecular hydrogen (H2) in the presence of a metal catalyst, is another major class of chemical reductions. Other approaches involve hydrosilanes, zinc/HCl, iron and nickel catalysts, and various metal oxides or salts that facilitate electron or hydride transfer. The choice of reagent depends on the substrate’s functional group and the desired degree of reduction.

Typical targets for chemoreduction include carbonyl groups (aldehydes and ketones) reduced to alcohols, esters and carboxylic acids to alcohols, nitro groups to amines, and imines to amines. Alkenes and some arenes can also be reduced under specific conditions, such as catalytic hydrogenation. Reaction selectivity, chemoselectivity, and functional-group tolerance are important considerations, often requiring protecting groups or tailored conditions.

Chemo- reduction plays a central role in organic synthesis, pharmaceutical development, and material science. Its practical implementation requires careful control of reagents, solvents, temperature, and workup to achieve the desired transformation with safety and efficiency.