Formation of Pyrido[3, 2-f]quinoxalines by Reaction of 6-Amino-2, 3-dimethylquinoxaline with Aldehydes

Abstract

The reaction of 6-amino-2, 3-dimethylquinoxaline (1) with acetaldehyde in ethanol proceeded at refluxing temperature to give 10-ethoxy-2, 3, 8-trimethyl-7, 8, 9, 10-tetrahydropyrido[3, 2-f]quinoxaline (2), which was converted to 2, 3, 8-trimethylpyrido[3, 2-f]quinoxaline (4) and 2, 3, 8-trimethyl-7, 8, 9, 10-tetrahydropyrido[3, 2-f]quinoxaline (5) in an acidic medium. Crotonaldehyde also reacted smoothly at room temperature with 1 to afford several pyrido[3, 2-f]quinoxaline derivatives along with 4 and 5.