An improved process for preparing imidazoles by contacting glyoxal or methyl substituted derivatives thereof, formaldehyde, and an ammonium salt of an acid having an ionization constant greater than 1 .times. 10.sup.-.sup.3.
A process for the preparation of 4-methylimidazoles by reacting methylglyoxal with ammonia and an aldehyde in aqueous solution, wherein the reaction is carried out at a pH of above 7 and either the reactants are all brought into contact simultaneously or the aldehyde and the methylglyoxal are added simultaneously to the aqueous ammonia solution.
The method is for manufacturing imidazoles corresponding to the general formula: ##STR1## in which R represents hydrogen or an alkyl radical of 1 to 17 carbon atoms. Glyoxal is condensed with an aliphatic aldehyde and ammonia, in a hydroalcoholic medium at a pH comprised between 6 and 8. The glyoxal is in the form of its bisulfite combination and the ammonia being supplied by an ammonium salt of a weak acid.
A process for the preparation of 5-methyl-4-imidazolecarboxylic acid esters from acetoacetic acid esters. The products of this process are useful as intermediates for preparing cimetidine.
Imidazoles may be manufactured by reacting a glyoxal, ammonia, an aldehyde, and optionally a primary amine, in the presence of a Bronsted acid whose pKa is approximately equal to the pKa of the ammonium cation of the primary amine, or if the primary amine is not present, to the pKa of the ammonium (NH.sub.4.sup.+) cation. The reaction may be used to make in relatively high yields a wide variety of imidazoles using relatively inexpensive starting materials. The imidazoles are useful as chemical intermediates.
A process for the preparation of 5-methyl-4-imidazolecarboxylic acid esters from acetoacetic acid esters. The products of this process are useful as intermediates for preparing cimetidine.
