Influence of catalyst type, solvent, acid and base on the selectivity and rate in the catalytic debenzylation of 4-chloro-N,N-dibenzyl aniline with Pd/C and H-2

The influence of catalyst type, solvent, and acid/base modifiers on the catalytic debenzylation of 4-chloro-N,N-dibenzyl aniline with Pd/C and H-2 was studied. Under the reaction conditions investigated, the catalyst-type had no significant effect. Solvents: In neutral apolar solvents, the over-all reaction was slow and the main product isolated after 1.9 mol H-2-uptake was always 4-chloroaniline. No high intermediary concentration of 4-chloro-N-benzyl aniline (monodebenzylation product) was found. In polar solvents, both debenzylation and dehalogenation were much faster. After 1.9 mol H-2-uptake, significant amounts of the dehalogenation product aniline were found. Catalytic amounts of strong acids significantly increased the rate for debenzylation and dehalogenation was suppressed. With equimolar amounts of strong acid, the debenzylation was slower, but high intermediary amounts (> 80%) of the monodebenzylation product could be isolated. A kinetic model to rationalize these effects was developed.