Cobalt-catalyzed amination of 1,3-cyclohexanediol and 2,4-pentanediol in supercritical ammonia

The one-step procedure of amination of bifunctional secondary alcohols to d iamines has been investigated in a continuous fixed-bed reactor. Applicatio n of supercritical NH3 as a solvent and reactant suppressed catalyst deacti vation and improved selectivities to amino alcohol intermediates, whereas s electivities to diamines remained poor (8-10%). The main reason for the low diamine selectivity of 1,3-dihydroxy compounds is water elimination leadin g to undesired monofunctional products via alpha,beta-unsaturated alcohol, ketone or amine intermediates. This side reaction does not occur with 1,4-d ihydroxy compounds which afford high aminol and diamine selectivities under similar conditions. Amination of secondary diols with ammonia was found to be faster, but less selective than that of the corresponding primary 1,3-p ropanediol.