Debenzylation transfer hydrogenolysis

N,N-Debenzylation was accomplished by Pd/C and HC02NH4.349 Debenzy-lation of an N,N-dibenzyltryptamine derivative was sluggish and incomplete using Pd/C as the catalyst. In contrast, transfer hydrogenolysis using ammonium formate-formic acid in the presence of Pd black efficiently afforded the free tryptamine (27) (Scheme 4.102).350... 

Dibenzylpyrimidine 387 was monodebenzylated under transfer hydrogenolysis conditions to give 388 in 60% yield (Scheme 115).[ The imide benzyl group was slower to react but did get ranoved after 48 h at reflux and 300 wt % catalyst loading to give the completely debenzylated product in 78% yield. 

Nitrogen on heterocycles has frequently been protected as the Af-benzyl derivative. Thus, 2-benzylimidazole 399 was successfully debenzylated to 400 in excellent yield (Scheme 118).[i i It should be noted that the benzylic ketone in 399 was not hydrogenated. Transfer hydrogenolysis with ammonium formate was also effective for the removal of the benzyl group in A -benzyl-2-methylimidazole. 

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