Catalytic Synthesis of Amines A Reductive Amination Process

Abstract

The objective of present work was to develop a method for N-alkylation of amines using newlineautohydrogen transfer reaction. The implicity of the reaction, easy of application, available starting material, no net oxidation-reduction, fewer reaction steps, greener in terms of the limited byproducts and with a wide range of catalyst system developed makes the reaction a preferred choice for a chemist and industrialist. Raney nickel was chosen as the catalyst for the study. Three grades of Raney Nickel (W4, T4 and W7) were Prepared, Characterized and newlineEvaluated for its efficiency for N-alkylation of Aniline with Benzyl alcohol. A suitable newlineanalytical method was developed on Gas chromatography and validated. The developed newlinemethod was used for reaction monitoring. The difference in the reactivity of the different newlinegrades could be attributed to the Aluminum content in the catalyst. On studying the reaction mechanism it was observed that the reaction follows dehydrogenation of alcohol to aldehyde, followed by condensation of aldehyde with amine to form imine and in the final step the imine is reduced to N-alkylated amine using the hydrogen released in dehydrogenation step. The dehydrogenation and hydrogenation step were catalyst dependent steps. On comparing the rate of reaction it was observed that dehydrogenation was the rate limiting step. The reaction parameters were optimized to obtain maximum yield. On removing water from the reaction the selectivity of the reaction was enhanced. The increase in catalyst concentration resulted in increased yields. At lower concentration of alcohol imine was the newlinemajor product formed and at higher concentrations dialkylation of the amines takes place. Various aprotic solvents have been used and the effects on the yield were studied, it was observed that xylene was the preferred solvent. Addition of base to the reaction retarded the reaction rate.