Mixture of 2-cyano-7-acetoxy-6-methoxy-3-(3,4,5-trimethoxybenzoyl)-benzo[b]furan (15 mg, 0.04 mmol) ammonium chloride (11 mg, 0.2 mmol) and sodium azide (13 mg, 0.2 mmol) in dry DMF (400 μL) was stirred at 110° C. for 4 hours. More sodium azide (15 mg, 0.23 mmol) was added and stirring was continued for 1 hour (tlc), quenched with saturated ammonium chloride solution and extracted with ethyl-acetate (10 mL×2). The organic layer was dried over magnesium sulfate and solvent was distilled and the crude was purified by silica gel plate to afford the title compound as creamy solid; (3.5 mg, 21%; 1H NMR (300 MHz, CDCl3) δ: 7.85(1H, NH), 7.26(d, J=8.54 Hz, 1H), 7.02(s, 2H, benzoyl Hs), 6.95(d, J=8.54 Hz, 1H), 5.74(b, 1H, OH), 3.97(s, 3H, OMe), 3.88(s, 3H, OMe), 3.82(s, 6H, 2×OMe).
