Unsymmetrical salen-type ligands: high yield synthesis of salen-type Schiff bases containing two different benzaldehyde moieties
作者:E.Joseph Campbell、SonBinh T Nguyen
DOI:10.1016/s0040-4039(00)02226-7
日期:2001.2
Salen-type Schiff base ligands incorporating two different benzylidene moieties and a diamine backbone were synthesized in high yield (80-90%) under mild conditions via a stepwise approach. Tn the first step, anhydrous hydrochloric acid was used to selectively protect one amino group of the vicinal diamine backbone. The resulting ammonium salt was added to a substituted benzaldehyde providing access to a mono-imine product. This compound reacted with an equivalent of a different benzaldehyde in the presence of triethylamine to afford an unsymmetrical salen-type ligand. This synthetic method allows facile access to a plethora of salen-type Schiff base ligands with easily tunable steric and electronic properties. (C) 2001 Elsevier Science Ltd. All rights reserved.