Solvent-free direct α-alkylation of ketones by alcohols catalyzed by nickel supported on silica–alumina?

Green Chemistry Pub Date: 2018-08-27 DOI: 10.1039/C8GC01958D

Abstract

The α-alkylation of acetophenone with benzyl alcohol through borrowing hydrogen has been studied using nickel catalysis. Ni/SiO2-Al2O3 was found to be the best catalyst for this transformation and the corresponding alkylated acetophenone was obtained with 93% isolated yield. Following the objectives of clean and sustainable chemistry, the reaction occurs under solvent-free conditions and requires only a catalytic amount of base. This protocol was next applied to a wide range of ketones and alcohols and the desired products were isolated with 18–86% yields (26 examples). The recovery and recyclability of the nickel catalyst was also investigated and it was found to be active over 5 runs without significant loss of activity. Surprisingly, the active catalyst appears to include an amorphous nickel hydroxide layer.

Graphical abstract: Solvent-free direct α-alkylation of ketones by alcohols catalyzed by nickel supported on silica–alumina
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