THE MECHANISMS OF THE FORMATION OF BY-PRODUCTS IN THE CATALYTIC SYNTHESIS OF C-ALKYLIMIDAZOLES FROM DIAMINES AND CARBOXYLIC-ACIDS

The formation of 1-ethyl-2-methylimidazole (I-Et-2-MI) and 1-ethyl-2-m ethylimidazoline (1-Et-2-MIN), intermediates in the synthesis of 2-met hylimidazole (2-MI) from ethylenediamine (EDA) and AcOH in the presenc e of a platinum-on-alumina catalyst, was studied. Using (CH3COOH)-C-14 the incorporation of two acetate units into 1-Et-2-MI and 1-Et-2-MIN molecules was demonstrated. The same products were also obtained on de hydrogenation of 2-methylimidazoline (2-MIN) under mild conditions (22 0-230-degrees-C). A part of the latter is transformed to N-ethyl ethyl endiamine (EEDA) and EDA. These facts indicate that both 1-Et-2-MI and 1-Et-2-MIN result from hydrogenolysis of the imidazoline ring with su bsequent ethylation. A reverse reaction, the C5-cyclization of EEDA, w as also observed. The formation of 2-MI is favored by increasing tempe rature.