Secondary aromatic amines crystalline derivatives

Schotten-Baumann reaction, 582, 584, 780, 784 see also Benzoates Sebacic acid, 469, 938,939 Secondary aliphatic amines, 413 crystalline derivatives of, 422 reactions of, 421, 1072 table of and derivatives of, 424 Secondary alkaryl amines, 562, 570, 571 Secondary aromatic amines, 559, 562 crystalline derivatives of, 652 reactions and characterisation of, 649 1173 ... 

Secondary amines can be prepared from the primary amine and carbonyl compounds by way of the reduction of the derived Schiff bases, with or without the isolation of these intermediates. This procedure represents one aspect of the general method of reductive alkylation discussed in Section 5.16.3, p. 776. With aromatic primary amines and aromatic aldehydes the Schiff bases are usually readily isolable in the crystalline state and can then be subsequently subjected to a suitable reduction procedure, often by hydrogenation over a Raney nickel catalyst at moderate temperatures and pressures. A convenient procedure, which is illustrated in Expt 6.58, uses sodium borohydride in methanol, a reagent which owing to its selective reducing properties (Section 5.4.1, p. 519) does not affect other reducible functional groups (particularly the nitro group) which may be present in the Schiff base contrast the use of sodium borohydride in the presence of palladium-on-carbon, p. 894. 

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