Preparation and reactions of pyrrolo[1,2-a]quinoxalinesulphonic acids

Abstract

The major product of sulphonation of pyrrolo[1,2-a]quinoxaline at 130° is the 2-sulphonic acid. The nitro-group of the 1-nitro-3-sulphonic acid is very readily displaced by a chlorine atom by treatment either with concentrated hydrochloric acid or with lithium chloride in dimethylformamide. The corresponding reactions with hydrobromic acid and lithium bromide are more complex; for example, in hydrobromic acid, a mixture of 2,3-dibromo- and 1,2,3-tribromo-pyrrolo[1,2-a]quinoxalines is formed.