Process for preparing symmetrical and unsymmetrical N,N-dihydrocarbylhydroxylamines

A process for preparing an N,N-dihydrocarbylhydroxylamine of the general formula (I):

• wherein R1, R2, R3 and R4 each independently represent a moiety selected from the group consisting of branched or unbranched aliphatic, cycloaliphatic, heteroaromatic and aromatic radicals having from 1 to 32 carbon atoms, or R1 and R2 and/or R3 and R4 are joined to form a ring having a total of from 3 to 12 carbon atoms, the process comprising:
• a) reacting hydroxylamine H2NOH or a salt of hydroxylamine with a compound of the general formula (II) or (III)
• where R1, R2, R3 and R4 are as defined in formula (I) to form an oxime intermediate,
• b) hydrogenating the oxime intermediate in the presence of a catalyst comprising a noble metal to a hydrogen consumption of from 60 to 130 mol % of theory, to form a corresponding monohydrocarbylhydroxylamine or a salt of the corresponding monohydrocarbylhydroxylamine, and
• c) reacting the monohydrocarbylhydroxylamine or salt thereof with a compound of the general formula (II) or (III) with hydrogenation of the reaction mixture in the presence of a catalyst comprising a noble metal to a hydrogen consumption of from 60 to 130 mol % of theory, forming a corresponding dihydrocarbylhydroxylamine or a salt of the corresponding dihydrocarbylhydroxylamine,
• with the proviso that where a salt of hydroxylamine is reacted with a compound of the general formula (II) or (III), the process further comprises reacting of the salt of dihydrocarbylhydroxylamine with a base.