GB753500A - N, n-dibenzyl ethylenediamine - Google Patents

Abstract

N,N1-dibenzyl ethylenediamine is prepared by hydrogenating N,N1-dibenzylidene ethylenediamine in the presence of a supported palladium catalyst. The hydrogenation may be carried out at normal or elevated temperatures and pressures, temperatures between about 20 DEG and about 45 DEG C. and pressures of about 0-300 pounds per square inch gauge being specified. The reaction may be carried out in an inert diluent such as methanol or ethanol and vigorous agitation is beneficial. The palladium catalyst is supported, for example, on charcoal or alumina, and 5 per cent palladium on alumina is specified. The amount of catalyst used preferably gives about 0.25-1 per cent of palladium by weight of N,N1-dibenzylidene ethylenediamine used. The hydrogenation product contains some 1:3-dibenzyl-2-phenyltetrahydroimidazole which is decomposed by acids to give N,N1-dibenzyl ethylenediamine and benzaldehyde. The hydrogenation product is therefore hydrolysed with, for example, sulphuric or acetic acid, the benzaldehyde removed, and the N,N1-dibenzyl ethylenediamine salt recovered. The salt may be purified by liberation of the free base, extraction of the base by a solvent such as butyl acetate, treatment of the base solution with decolourizing carbon, and the extract treated with an acid to give the corresponding salt. In examples (1) and (2) the hydrogenation is carried out in methanol using a palladium or alumina catalyst, at a temperature of about 30-45 DEG C. and at a pressure of 3.4 atmospheres until absorption of hydrogen ceases, the methanol is removed by distillation in vacuo and the residue boiled with sulphuric or acetic acid, the salt being obtained on cooling; (3) under conditions similar to those used in (1) and (2) a 5 per cent palladium on alumina catalyst is compared with the corresponding platinum catalyst; (4) the hydrogenation is carried out as in (1) but largely at 0 pound per square inch gauge and at 28 DEG C.