Hydrochloric Acid → Isobutyl (2-chloropyridin-3-yl)sulfonyl(3-methoxy-5-methylpyrazin-2-yl)carbamate

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Reaction Steps

Sodium hydride (60% dispersion in oil; 0.083 g) was added to a stirred solution of isobutyl N-(3-methoxy-5-methylpyrazin-2-yl)-carbamate (0.451 g) in dry N,N-dimethylformamide (DMF; 8 ml) at 4° C. The mixture was stirred whilst warming to ambient temperature over 1 hour, was recooled to 4° C. and 2-chloropyridine-3-sulphonyl chloride (0.40 g) was added in portions over 2 minutes. The mixture was allowed to warm to ambient temperature and stirred a further 30 minutes. Water (40 ml) was added, followed by 1M hydrochloric acid to acidify. This mixture was extracted with ethyl acetate (4×15 ml) and the organic extracts were washed with water (10 ml) and saturated sodium chloride solution (10 ml) and then dried (MgSO4). Volatile material was removed by evaporation and the residue was purified by gradient elution with 0-35% ethyl acetate/hexane through a silica gel Mega Bond Elut column and triturated with ether to give 2-chloro-N-isobutoxycarbonyl-N-(3-methoxy-5-methylpyrazin-2-yl)-pyridine-3-sulphonamide (0.34 g) as a solid, m.p. 99-101° C.; 1H NMR (CDCl3): 0.7 (d, 6H), 1.7 (m, 1H), 2.5 (s, 3H), 3.8 (d, 2H), 4.0 (s, 3H), 7.45 (dd, 1H), 7.9 (s, 1H), 8.6 (dd, 1H), 8.7 (dd, 1H); mass spectrum (+ve ESP): 415 (M+H)+.

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