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

Abstract

The synthesis of asymmetric secondary amines (ASA) is commonly achieved by N-alkylation of primaryamines with alcohols. Here, we investigated the ASA synthesis via the direct amination of alcohols withnitriles, 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, isobutanoland n-octanol) and secondary (2-propanol, 2-butanol and 2-octanol) alcohols was studied onSiO2-supported Co, Ni and Ru catalysts. Competitive BN hydrogenation-condensation reactions formeddibutylamine (the symmetric secondary amine) and tertiary amines as main secondary products. OnCo/SiO2, the ASA selectivities for BN/primary alcohol reactions were between 49 and 58% at completeBN 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, therebyshowing that the alcohol amination with nitriles is an attractive alternative route for the synthesis ofvaluable asymmetric secondary amines.