Dichloromethane → 3-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyloxy)-4-[(4-bromo-2-methyl-phenyl)methyl]-5-isopropyl-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

4-[(4-Bromo-2-methyl-phenyl)methyl]-5-isopropyl-1H-pyrazol-3-ol (110 g, 356 mmol), 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide (204.8 g, 498 mmol), benzyltributylammonium chloride (17.2 g, 53.4 mmol), potassium carbonate (122.9 g, 889 mmol), dichloromethane (1100 mL), and water (330 mL) are combined and the mixture is stirred at 50° C. temperature for 16 hours. Further 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide (29.26 g, 71.2 mmol) is added and the mixture stirred at 55° C. for 3 hours. The mixture is cooled to ambient temperature and stirred overnight. Further 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide (29.26 g, 71.15 mmoles) is added and the mixture is heated to reflux for 1.5 hours. The mixture is cooled to ambient temperature and water (2000 mL) is added. The phases are separated and the aqueous is extracted with dichloromethane (500 mL). The combined organic layers are washed with water (2000 mL) and saturated aqueous NaCl solution (2000 mL). The solution is dried over MgSO4 and filtered. The filtrate is concentrated under reduced to provide a solution of approximately 500 mL. This solution is poured onto a silica column and is purified by flash chromatography (5 Kg silica), eluting first with 100% dichloromethane, then with 40% ethyl acetate/dichloromethane, to provide the title compound (175 g, 77% yield). Mass spectrum (m/z): 639/641 (M+1).

Provenance & Evidence