Wet SiO₂As a Suitable Media for Fast and Efficient Reduction of Carbonyl Compounds with NaBH₃CN under Solvent-Free and Acid-Free Conditions

Abstract

Reduction of carbonyl compounds such as aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones and acyloins was carried out readily with NaBH3CN in the presence of wet SiO2 as a neutral media. The reactions were performed at solvent-free conditions in oil bath (70 -80 o C) or under microwave irradiation (240 W) to give the product alcohols in high to excellent yields. Regioselective 1,2-reduction of conjugated carbonyl compounds took place in a perfect selectivity without any side product formation.

Selective aldehyde reductions in neutral water catalysed by encapsulation in a supramolecular cage

“…Indeed, reductions of aldehydes to the corresponding alcohols by the mild reducing agent sodium cyanoborohydride are generally held to work effectively only in acidic solutions. 29 This suggested to us that if the aldehyde was indeed encapsulated by the anionic Fe 4 L 6 cage, and if such cages were indeed capable of stabilising protonated substrates (which might normally only form to a significant degree in acid solution), then reactions that would otherwise require acidic conditions might occur in the presence of cage, even though the medium outside the cage might be neutral (or even basic).…”

Sulfonic acid anchored on silica, SiO2@SO3H: A superior solid acid catalyst for quick and solvent‐free reductive‐deoxygenation of ketones with NaBH3CN

“…This situation puts some restrictions to use NaBH 3 CN for bench‐top and practical purposes. To overcome the mentioned drawbacks, we recently introduced wet SiO 2 as a solid acid promoter for reduction of carbonyl compounds with NaBH 3 CN under acid‐free and solvent‐free conditions . Although the reported method has own merits; however, the requirement for oil bath (70–80°C) conditions (accompanied with the prolonged reaction times) or microwave irradiation as an unconventional energy source are its disadvantages.…”

“…To overcome the mentioned drawbacks, we recently introduced wet SiO 2 as a solid acid promoter for reduction of carbonyl compounds with NaBH 3 CN under acid-free and solvent-free conditions. [23] Although the reported method has own merits; however, the requirement for oil bath (70-80 C) conditions (accompanied with the prolonged reaction times) or microwave irradiation as an unconventional energy source are its disadvantages. Therefore, keeping a new strategy in mind encouraged us to investigate the promoter activity of sulfonic acid anchored on silica as a new solid acid catalyst for enhancing the reducing capability of NaBH 3 CN.…”

A New and Convenient Method for Reduction of Oximes to Amines with NaBH3CN In the Presence of MoCl5/NaHSO4·H2O System

“…9 This success encouraged us to investigate reduction of oximes with NaBH 3 CN in the absence of any acidic conditions.…”