Selective one-pot synthesis of asymmetric secondary amines via N-alkylation of nitriles with alcohols

The synthesis of asymmetric secondary amines (ASA) is commonly achieved by N-alkylation of primary amines with alcohols. Here, we investigated the ASA synthesis via the direct amination of alcohols with nitriles, which avoids the synthesis, separation and purification of the primary amines in a first step. Specifically, the ASA synthesis via N-alkylation of butyronitrile (BN) with primary (n-propanol, iso-butanol and n-octanol) and secondary (2-propanol, 2-butanol and 2-octanol) alcohols was studied on SiO2-supported Co, Ni and Ru catalysts. Competitive BN hydrogenation-condensation reactions formed dibutylamine (the symmetric secondary amine) and tertiary amines as main secondary products. On Co/SiO2, the ASA selectivities for BN/primary alcohol reactions were between 49 and 58% at complete BN conversion, forming dibutylamine and tertiary amines as byproducts. For BN/secondary alcohol reactions, Co/SiO2 formed selectively (ASA + dibutylamine) mixtures containing 78-85% of ASA, thereby showing that the alcohol amination with nitriles is an attractive alternative route for the synthesis of valuable asymmetric secondary amines. (C) 2019 Elsevier Inc. All rights reserved.