ContinuousN-alkylation reactions of amino alcohols using γ-Al2O3and supercritical CO2: unexpected formation of cyclic ureas and urethanes by reaction with CO2.
The use of γ-Al2O3as a heterogeneous catalyst in scCO2has been successfully applied to the amination of alcohols for the synthesis ofN-alkylated heterocycles. The optimal reaction conditions (temperature and substrate flow rate) were determined using an automated self-optimising reactor, resulting in moderate to high yields of the target products. Carrying out the reaction in scCO2was shown to be beneficial, as higher yields were obtained in the presence of CO2than in its absence. A surprising discovery is that, in addition to cyclic amines, cyclic ureas and urethanes could be synthesised by incorporation of CO2from the supercritical solvent into the product.
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
Emilia S
ES
Streng
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
Darren S
DS
Lee
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, 199 Taikang East Road, Ningbo 315100, China.
Michael W
MW
George
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
Martyn
M
Poliakoff
N-alkylation; continuous flow; heterocycle; self-optimisation; supercritical CO2