Patent ID: 6353115
Filing Date: 2002-03-05
Classification: C07D

Abstract:
A process for preparing carbonyldiimidazoles of the formulae Ia, Ib, Ic or mixtures thereof where R1 is hydrogen or a C1-4-alkyl radical and R2 is hydrogen or a methyl radical, by reacting at least one imidazole of the formulae IIa and IIb in which R1 and R2 have the abovementioned meaning, with phosgene in an inert solvent, which comprises adding to the reaction mixture, based on the imidazoles, stoichiometric amounts of an organic nitrogen base which has a lower pKb than imidazole, wherein the carbonyldiimidazole which is formed is crystallized out by cooling the reaction mixture and is removed as solid, while the hydrochloride which is formed from the nitrogen base remains in the organic solution, the hydrochloride of the nitrogen base is neutralized with a stronger aqueous organic base to return to the free base, which remains in the organic solvent, and wherein the liberated nitrogen base in the organic solvent is separated from the aqueous phase and recycled to the synthesis, wherein the nitrogen base employed is a tertiary amine of the general formula NR3 where the R radicals are each, independently of one another, branched or unbranched C1-10-alkyl, or two of the radicals form with one nitrogen atom a 5- or 6-membered heterocycloaliphatic or heteroaromatic ring.