Facile Synthesis of Naphtha-quinoxaline Derivatives from ß-lapachone Using Graphene Oxide as Catalyst.

OBJECTIVE: To develop efficient method for the synthesis of naphtha-quinoxaline derivatives via the reaction of ß-lapachone with various 1,2-diamines. METHODS: A mixture of ß-lapachone (1mmol), 1,2-diamine (1mmol) and graphene oxide (20mg) in methanol (3mL) was heated at 60°C, under constant stirring for appropriate time. After completion of the reaction, the catalyst was filtered off, washed with ethyl acetate (3x3mL) and the combined filtrate was washed with H2O, dried (anhy. Na2SO4) and concentrated under vacuum. The residue was chromatographed over a column of silica gel eluting with a mixture of hexane and ethyl acetate in different ratios, to afford the desired product. All synthesized compounds were assigned with the help of analytical and 1H, 13C NMR, IR, and mass spectral studies. RESULTS: To establish the catalytic role of GO in the synthesis of naphtha-quinoxaline derivatives, the reaction of ß-lapachone with 3,4-diaminotoluene was selected as a model reaction. The catalytic activity of graphene oxide in comparison with other catalysts like acidic resin amberlyst-15 and solid acid catalyst like montmorillonite K-10 were studied. The reaction was also observed in various solvents such as water, acetonitrile, toluene, dichloromethane, ethanol and 1,4-dioxane using GO as a catalyst. Excellent yields were obtained at 60°C in methanol. The efficacy of the present protocol was investigated by the reaction of ß- lapachone with other 1,2-diamines. CONCLUSION: An attractive green metal free carbocatalyst Graphene Oxide (GO) has been successfully utilized for the expedient synthesis of naphtha-quinoxaline derivatives. GO showed high catalytic activity which is attested by the desired products being produced in shorter time. The main advantage of this method is the reusability of the catalyst which makes the procedure sustainable.