Sodium Dithionite → N-[(4aR,6R,8aS)-8a-(5-bromo-2,4-difluorophenyl)-6-(hydroxymethyl)-4,4a,5,6,8,8a-hexahydropyrano[3,4-d][1,3]thiazin-2-yl]benzamide

Participants

Reaction Steps

A solution of C9 (3.22 g, 5.48 mmol) in ethyl acetate (100 mL) was treated with a solution of sodium bromate (4.14 g, 27.4 mmol) in water (66 mL). To the well stirred biphasic system was added a solution of sodium dithionite (4.77 g, 27.4 mmol) in water (134 mL) drop-wise over 30 minutes. The reaction mixture was stirred for 90 minutes and then diluted with ethyl acetate (500 mL). The organic layer was removed and the aqueous was extracted with ethyl acetate (3×100 mL). The combined organics were then washed with an aqueous solution of sodium thiosulfate pentahydrate (3×300 mL), brine (300 mL), and then dried over sodium sulfate, filtered and concentrated in vacuo. Silica gel chromatography (Gradient: 0% to 100% ethyl acetate in heptane) provided the product as a white solid. Yield: 1.77 g, 3.57 mmol, 65%. LCMS m/z 499.1 [M+H+], Br isotopic pattern. 1H NMR (400 MHz, CD3OD), characteristic peaks: δ 8.11 (d, J=6.5 Hz, 2H), 7.64 (t, J=7.9 Hz, 1H), 7.53-7.57 (m, 1H), 7.44-7.48 (m, 2H), 7.24 (dd, J=12, 8.3 Hz, 1H), 4.09 (dd, J=11.6, 1.9 Hz, 1H), 3.9 (d, J=11.9 Hz, 1H), 3.72-3.77 (m, 1H), 3.58 (d, J=5.1 Hz, 2H), 3.11-3.19 (m, 1H), 2.97 (dd, J=13.3, 4.1 Hz, 1H), 2.75 (dd, J=13.1, 2.7 Hz, 1H), 1.84 (q, J=11.6 Hz, 1H), 1.66-1.71 (m, 1H).

Provenance & Evidence