Ruthenium hydroxide supported on magnetic nanoparticles: a benign aqueous protocol for hydration of nitriles

Amides are an important class of compounds in the chemical and pharmaceutical industry (1,2). Conventionally, amides have been synthesized by the hydration of nitriles, catalyzed by strong acids (3) and bases (4). Many by-products such as carboxylic acids are produced due to hydrolysis of the starting nitriles and amides under these conditions. Also, several sensitive functional groups do not tolerate such harsh conditions, which results in a decrease in the selectivity of the reaction protocol. Numerous processes using homogeneous metal complexes have been reported for this hydration protocol (5). However, these suffer from various drawbacks, such as difficulty in separation of product and catalyst from the reaction mixture, as well as the use of inert atmosphere for handling air-sensitive metal catalysts. Heterogeneous systems have been reported, such as alumina (6), potassium fluoride-doped Al2O3 (7) and phosphates (8), silica-supported manganese oxides (9), modified hydroxyapatite (10), and ruthenium hydroxide coated on alumina and ferrites (11). However, turnover numbers of these protocols are still small and reusability of the catalyst is intricate. A recently developed hydration protocol in pure water is good in terms of reaction conditions and product yield (12), but it still needs traditional work-up using toxic organic solvents to isolate the product and uses expensive ruthenium complexes as catalysts.