Diboron compounds as reductants in hydrogenation, hydrofunctionalization and deoxygenation reactions.

Reduction reactions are among the most commonly employed methods in organic synthesis, both in the laboratory and industry. Typical reductants include hydrogen gas, as well as metal-, silicon-, and boron-based hydrides. Although hydrogen gas is considered the greenest reductant, its production currently depends heavily on fossil fuel-derived processes. Metal-, silicon-, and boron-hydrides are effective but often inconvenient to handle, and their preparation is energy-intensive. In recent decades, the use of diboron compounds as reductants has gained increasing attention. These compounds can generate hydrogen gas from protic solvents effectively for hydrogenation reactions and can also be used for hydrofunctionalization and deoxygenation transformations. This review highlights various types of diboron compounds, elucidates their mechanisms in these transformations, and discusses representative examples from recent literature.