Design and Synthesis of Two Aromatic Amines with Dendritic Structure

The design and synthesis of two aromatic amines with dendritic structures, i.e. 3,4,5-tribenzyloxyaniline (3,4,5-G₁-NH₂) and 2,5-dibenzyloxyaniline (2,5-G₁-NH₂), were conducted. A coupling reaction of three or two equivalents of benzyl bromide to one equivalent of methyl hydroxybenzoate generated methyl 3,4,5-tribenzyloxybenzoate (3,4,5-G₁-COOCH₃), methyl 2,5-dibenzyloxybenzoate (2,5-G₁-COOCH₃) and 2,6-dibenzyloxybenzoate (2,6-G₁-COOCH₃) in high yields. All G₁-COOCH₃ derivatives were studied by X-ray analysis. The results show that these dendrons have sufficient volume to be used as the fine ligands for certain catalysts. The amide intermediates (benzamide, G₁-CONH₂) were obtained by reaction between ammonia and G₁-COOCH₃. Interestingly, 2,6-dibenzyloxybenzamide (2,6-G₁-CONH₂) can not be prepared in the same condition, which may be due to the overlarge steric block. Sodium hypochlorite was an effective oxidant to generate methyl carbamates G₁- NHCO₂CH₃.