Three-component couplings for the synthesis of pyrroloquinoxalinones by azomethine ylide 1,3-dipolar cycloaddition chemistry

1-Methyl-3,4-dihydroquinoxalin-2(1H)-one was heated with a range of aldehydes to generate intermediate azomethine ylides which underwent 3 + 2] cycloaddition reactions with N-methyl or N-phenylmaleimide to give substituted tetrahydropyrroloquinoxalinones. Only one (racemic) stereoisomer was formed in each case and the stereochemical outcome was verified by single crystal X-ray analysis. The products from this multicomponent reaction could be oxidised with DDQ to the pyrroloquinoxalinones.