Toward Renewable Amines: Recent Advances in the Catalytic Amination of Biomass-Derived Oxygenates

Synthesis of high-value-added chemicals from biomass and/or biomass-derived platform molecules is considered an important strategy to mitigate the global dependency on fossil resources and include renewable resources in a circular economy. In recent years, the synthesis of bio-based plastics has received significant attention as a potential alternative to conventional industrial processes. Thus, a lot of effort has been put into the development of not only different classes of biomonomers but also bio-based drop-in chemicals. Amine-derived molecules, especially alcohol-amines, diamines, and N-heterocyclic amines, are the most important classes of functional monomers for the production of polyamides, polyimides, polyurethanes, and polyureas. Additionally, these amines are extensively used in pharmaceuticals. In this review, we will give a concise overview of the up-to-date methods for the production of industrially important amines from biomass-derived oxygenates. Special attention will be given to the catalytic amination of biomass aldehyde- and alcohol-based oxygenates, reaction mechanism, catalyst stability, as well as their specific challenges and opportunities. We anticipate this critical and comprehensive review to provide detailed insights into the synthesis of bio-based amines and guide the development of effective greener synthetic methodologies

Modulating Catalytic Selectivity by Base Addition in Aqueous Reductive Amination of 1,6-Hexanediol Using Ru/C

Efficient base-modulated product selectivity in the aqueous-phase Ru/C-catalyzed reductive amination of 1,6-hexanediol (HDO) was reported by performing the reaction at mild conditions (463 K, 25 bar H2). High selectivity of amines could be controlled by the addition of different bases; for example, Cs2CO3 addition gave a high yield of 6-amino-1-hexanol (AH, 26%). However, the addition of Ba(OH)2 resulted in the formation of high yield of secondary amination products, hexamethylenediamine (HMDA, 34%) and azepane (26%). The hydroxide base, especially Ba(OH)2, aids in the initial conversion of HDO to AH by significantly decreasing the apparent activation energy from 68 to 48 kJ mol–1. A closer analysis of the formation of secondary products (azepane and HMDA) revealed a faster reaction between NH3 and the carbonyl-containing intermediate by the addition of Ba(OH)2 into the reaction solution