The reaction of carbonyldiimidazole with alcohols to form carbamates and N-alkylimidazoles

The reactions of non-benzylic primary and secondary aliphatic alcohols with carbonyldiimidazole (CDI) afford the corresponding carbamates but not N-alkylimidazoles. For benzylic primary alcohols, formation of N-alkylimidazoles proceeds reasonably at 170 °C in several different solvents and occurs by way of the initially formed carbamate. However, under these rather forcing conditions, or even at lower reaction temperatures, elimination is a significant side reaction for benzylic secondary alcohols with β-hydrogen atoms. With one exception, reactions of six N,N-disubstituted β-aminoalcohols with CDI to form N-alkylimidazoles proceed under relatively mild conditions and may occur by way of an aziridinium intermediate.