Sodium sulfate decahydrate → (5-amino-7-bromo-3-chloro-8-fluoro-5H-chromeno[2,3-b]pyridin-5-yl)methanol

Participants

Reaction Conditions

Reaction Steps

A solution of 7-bromo-3-chloro-8-fluoro-5H-chromeno[2,3-b]pyridin-5-one (10.00 g, 30.4 mmol) and trimethylsulfonium iodide (6.83 g, 33.5 mmol) in 150 mL DMSO under argon atmosphere was treated with potassium tert-butoxide (3.76 g, 33.5 mmol) at rt. After 75 minutes, trimethylsilylazide (8.08 mL, 60.9 mmol) was added, and the reaction mixture was allowed to stir overnight. The reaction mixture was then diluted with EtOAc and washed with water. The suspension was filtered, and the filtrate was dried over MgSO4 and concentrated under reduced pressure. The crude residue was taken up in 100 mL THF and cooled to 0° C. LAH (1.155 g, 30.4 mmol) was added, and the reaction mixture was allowed to stir for 30 minutes. The ice bath was removed, and the reaction mixture was allowed to stir for an additional 30 minutes. The reaction mixture was then cooled back to 0° C. and quenched with sodium sulfate decahydrate (9.81 g, 30.4 mmol). After stirring for one hour, the reaction mixture was filtered through celite and concentrated under reduced pressure. Purification of the crude residue by column chromatography [0-80% (95:5 EtOAc/MeOH)/DCM] gave (5-amino-7-bromo-3-chloro-8-fluoro-5H-chromeno[2,3-b]pyridin-5-yl)methanol (2.83 g, 7.87 mmol, 25.9% yield). Step 2: A solution of (5-amino-7-bromo-3-chloro-8-fluoro-5H-chromeno[2,3-b]pyridin-5-yl)methanol (2.83 g, 7.87 mmol) and bromoacetonitrile (5.48 mL, 79 mmol) in 16 mL THF was heated to 40° C. and treated drop wise with lithium tert-butoxide [1N in THF (79 mL, 79 mmol)] over a time period of 4 hours. After completed addition the reaction mixture was concentrated under reduced pressure. Purification of the crude residue by column chromatography [0-40% (95:5 EtOAc/MeOH)/DCM] gave 2-((5-amino-7-bromo-3-chloro-8-fluoro-5H-chromeno[2,3-b]pyridin-5-yl)methoxy)acetonitrile (1.362 g, 3.42 mmol, 43.4% yield). Step 3: To a solution of 2-((5-amino-7-bromo-3-chloro-8-fluoro-5H-chromeno[2,3-b]pyridin-5-yl)methoxy)acetonitrile (1.363 g, 3.42 mmol) in 10 mL 2-MeTHF under nitrogen atmosphere was added trimethylaluminum [2N in heptane (3.42 mL, 6.84 mmol)]. After stirring for 10 minutes, the reaction mixture was heated to 80° C. overnight. The reaction mixture was then allowed to cool to RT, and quenched with MeOH. Saturated Rochelle's salt solution was added, and the reaction mixture was vigorously stirred for an additional hour. The organic layer was separated, washed with brine, dried over MgSO4 and concentrated under reduced pressure. Purification of the crude residue by column chromatography [0-80% (90:10:1 DCM/MeOH/NH4OH)/DCM] gave 7-bromo-3-chloro-8-fluoro-2′,6′-dihydrospiro[chromeno[2,3-b]pyridine-5,3′-[1,4]oxazin]-5′-amine (0.422 g, 1.059 mmol, 31.0% yield).

Provenance & Evidence