A rapid and efficient method for the reduction of quinoxalines

Abstract

Mono and di-substituted alkyl and aryl quinoxalines are rapidly reduced in high yield to their respective 1,2,3,4-tetrahydro-derivatives by borane in THF solution. In the case of the 2,3-di-substituted compounds, reduction is stereoselective yielding exclusively the cis-isomers. Sodium borohydride in acetic acid also reduces alkyl and aryl quinoxalines, but proceeds with lower yields and often produces side products. Sodium borohydride in ethanol reduces quinoxaline and 2-methylquinoxaline in high yield; however, the reaction is very slow, whereas 2,3-dialkyl and 2-aryl quinoxalines are not efficiently reduced by sodium borohydride in ethanol.