Benzoic acid, 2-hydrazinyl-, hydrochloride (1:1) → 8-Bromo-10H-benzo[4,5]furo[3,2-b]indole-1-carboxylic acid

To a solution of 5-bromo-3(2H)-benzofuranone (3.10 g, 14.6 mmol) [Ellingboe, J. et al., J. Med. Chem. 1992,35 (7), 1176-1183] in ethanol (100 mL) was added a solution of 2-hydrazinobenzoic acid hydrochloride (5.49 g, 29.1 mmol) in deionized water (200 mL). The mixture was stirred for one hour at room temperature and then allowed to sit while cooled (0° C.). Vacuum filtration and drying in vacuo afforded 3.65 g (72%) of the title compound as a brown solid: mp 195° C.(dec) which was used without further purification.