A versatile synthesis of 4,5-dihydropyrrolo[1,2-a]quinoxalines

The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.