Hydrochloric Acid → 7-bromo-3-chloro-1-fluoro-5-methylene-5H-chromeno[2,3-c]pyridine

Participants

Reaction Conditions

Reaction Steps

7-Bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-one (21.5 g, 65.4 mmol) was suspended in dry THF (300 mL) under nitrogen in an ice bath. Methylmagnesium bromide (3.0 M in diethyl ether, 36 mL, 108 mmol) was added in ˜12 mL portions allowing 10-15 minutes between additions. The mixture was stirred for a 15 minutes after the final addition. Saturated ammonium chloride (50 mL) was added carefully followed by diethyl ether (200 mL), ethyl aceate (200 mL), water (400 mL) and 2 N HCl (50 mL). The phases were mixed and separated and the organic dried with magnesium sulfate before evaporating to dryness under reduced pressure. The crude alcohol was dissolved in dry THF (300 mL) and treated with HCl (4.0 M solution in 1,4-dioxane, 16 mL, 64.0 mmol). The mixture was heated to 50° C. and stirred for 30 minutes. The crude reaction mixture was evaporated to dryness under reduced pressure. The crude tar was triturated with diethyl ether (200 mL) and stirred in an ice bath. A cream coloured solid precipitated within a few minutes. After 10 minutes the mixture was filtered through a sintered glass frit and dried under high vacuum to give the desired 7-bromo-3-chloro-1-fluoro-5-methylene-5H-chromeno[2,3-c]pyridine.

Provenance & Evidence