Intermolecular charge transfer facilitated synthesis and spectral characterization of Schiff bases of a weak nucleophile 2,3-diamino-1,4-naphthoquinone

A new synthetic protocol for the formation of novel Schiff bases between a weak nucleophile, 2,3-diamino-1,4-naphthoquinone and aldehydes has been developed with addition of hexamethylbenzene (HMB). The driving force for the reaction is the intermolecular CT interaction between HMB and DANQ resulting in enhancement of nucleophilicity as evidenced from spectral and ab initio calculations. The structure of the compounds was confirmed by UV-vis, IR, H-1 NMR, C-13 NMR and elemental analysis. The advantages of this procedure are mild reaction conditions, high yield of products, operational simplicity and easy work-up procedures.