Sulfamic Acid: A Mild, Efficient, and Cost-Effective Catalyst for Synthesis of Indoloquinoxalines at Ambient Temperature

<div><p></p><p>A simple, cost-effective method for synthesis of indoloquinoxalines from isatin and <i>o</i>-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.</p> </div>