Dimethylformamide → 3-Bromo-8-chloro-1,5-naphthyridine

Participants

Reaction Conditions

Reaction Steps

5-((5-bromopyridin-3-ylamino)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione. A 350 mL sealed tube was charged with 2,2-dimethyl-1,3-dioxane-4,6-dione (21.6 g, 150.0 mmol) and triethyl orthoformate (150 mL, 150.0 mmol). This was heated to 100° C., and stirred at this temperature for 2 hours. Reaction then cooled to 30° C. and 55-bromopyridin-3-amine (25.95 g, 150.0 mmol) added portion-wise. Reaction vessel resealed and mixture stirred at 100° C. for 3 hours. LC/MS shows completion. Reaction mixture was cooled to room temperature, diluted with hexane, filtered, and air dried to yield 5-((5-bromopyridin-3-ylamino)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione (41.5 g, 85% yield) as a yellow solid. MS [M+H]=327.0. Calc'd for C12H11BrN2O4=327.1. 2) 7-bromo-1,5-naphthyridin-4(1H)-one. A 500 mL round bottom flask equipped with a reflux condenser was charged with 5-((5-bromopyridin-3-ylamino)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione (10.5 g, 32.1 mmol) and diphenyl ether (84.5 mL, 32.1 mmol). This was heated to 250° C. in heating mantle and allowed to stay at this temperature for 1 hour. Reaction mixture was cooled to room temperature and diluted with 300 mL of Hexanes. This was heated to 60° C. and triturated in this system for 3 hrs to afford 7-bromo-1,5-naphthyridin-4(1H)-one (6.05 g, 84% yield) as a crude brown solid. This was used without further purification. MS[M+H]=227.0. Calc'd for C8H5BrN2O=225.0. 3) 3-bromo-8-chloro-1,5-naphthyridine. 7-bromo-1,5-naphthyridin-4(1H)-one (23.8 g, 105.8 mmol), acetonitrile (192 mL, 105.8 mmol), and DMF (2.05 mL, 26.5 mmol) were placed in a 3-necked round bottom flask set up with a reflux condenser. Argon bubbled through. Reaction mixture brought to reflux (˜95° C.). Oxalyl chloride (28.7 ml, 328.1 mmol) was added dropwise via addition funnel over 40 minutes and reaction allowed to stir at this temperature for 16 hrs. Reaction mixture cooled to 0° C. and basified to pH ˜8 with aqueous sodium bicarbonate solution. Product extracted with DCM (500 mL) three times. Organic layers combined, dried over sodium sulfate and concentrated to afford brown solid. This was purified by ISCO silica gel chromatography to afford 3-bromo-8-chloro-1,5-naphthyridine (3.6 g, 14% yield) as fluffy tan solid. MS[M+H]=245.0@. Calc'd for C8H4BrClN2=243.5.

Provenance & Evidence