Synthesis of a New Series of N,N’-Dimethyltetrahydrosalen (H2 [H2Me]salen) Ligands by the Reductive Ring-Opening of 3,3'-Ethylene-bis(3,4-dihydro-6-substituted-2H-1,3-benzoxazines)

A new series of N,N'-bis(2'-hydroxy-5'-substituted-benzyl)-N,N′-dimethylethane-1,2-diamines (N,N'-dimethyltetrahydrosalen) ligands were prepared in good yield by reduction of the respective 3,3'-ethylene-bis(3,4-dihydro-6-substituted-2H-1,3-benzoxazine) precursors with sodium borohydride . The ligands were characterized by IR, NMR, and elemental analysis, which showed the compounds to be consistent with the proposed structures. Ring-opening reactions of bis-1,3-benzoxazines in the presence of sodium borohydride to produce N,N’-dimethylated tetrahydrosalens (H2 [H2Me]salen) have not been reported in the literature.