Ball-Milling Technique for the Straightforward Synthesis of Nitriles from Aldehydes Using Poly(N-vinylimidazole): Is the Mechanochemical Procedure a Practical Metal- and Solvent-Free Synthetic Method?

Poly(N-vinylimidazole) is a synthetic functional polymer with good biocompatibility and biodegradability. This work demonstrated that it is an efficient and highly recyclable heterogeneous catalyst for preparing nitriles from aldehydes under metal free, halogen-free, and solvent-free conditions. The corresponding aliphatic and aromatic species contain different functional groups, and heteroaromatic and alpha,beta-unsaturated nitriles were isolated in good to high yields at room temperature using the planetary ball milling technique in the open air. Some merits can be implied for the new mechanosynthesis of nitriles, including (a) the good to high yields of various aldehydes, (b) avoidance of the use of toxic, costly metal-containing catalysts, and (c) reactions in the absence of toxic, hazardous, and flammable organic solvents. Poly(N-vinylimidazole) showed excellent recoverability, and the catalyst could be reused several times after regeneration with no significant reduction in its catalytic efficiency.