TEA (78 mg, 0.55 mmol) and DMAP (10 mg) were added to a solution of 4,5-difluoro-6-(2-fluoro-4-iodo-phenyl)-6,8-dihydro-imidazo[4′,5′:3,4]benzo[1,2-d]oxazol-7-one (I-15a: 80 mg, 0.178 mmol) in dry DCM (5 mL) at 0° C. and the resulting mixture was stirred for 15 minutes. This was followed by the addition of cyclopropanesulfonyl chloride (39 mg, 0.27 mmol) and stirring was continued for a further 3 hours at room temperature. The reaction was monitored by TLC (50% ethyl acetate in hexane). The reaction mixture was partitioned between water (50 mL) and ethyl acetate (50 mL). The organic layer was washed with brine, dried over anhydrous Na2SO4 and concentrated to afford the crude product. Purification by column chromatography on silica gel (20-30% ethyl acetate in hexane) afforded 65 mg of the product (65% yield). H1NMR (CDCl3, 300 MHz): δ 8.14 (s, 1H), 7.72-7.65 (m, 2H), 7.28-7.24 (m, 1H), 3.35-3.25 (m, 1H), 1.75-1.60 (m, 2H), 1.35-1.25 (m, 2H).
