Abstract
A simple, cost-effective method for synthesis of indoloquinoxalines from isatin and o-phenylenediamine employing a catalytic amount of sulfamic acid at ambient temperature is reported. Moreover, the method is applicable for a variety of isatins, ninhydrin, 4-hydroxynaphthaquinone, and 1,2-diketones. The key features of the protocol include rapid reactions with good yields, simple workup procedure, and easy isolation of products.
GRAPHICAL ABSTRACT
Notes
a Isolated yields.
b As catalyst is insoluble in water, extraction of reaction mixture with ethyl acetate is carried out for isolation of product.
Notes. Reaction conditions: Isatin/acenaphthoquinone/2-hydroxynaphthoquinone/ninhydrin (1 mmol), o-phenylene diamine (1 mmol), sulfamic acid (20 mol%), ethanol 10 mL; temp. = RT.
a Isolated yields.