Hydrogen Peroxide → HCID 86761962, compound

Participants

Reaction Steps

A solution of 7-bromo-3-chloro-5H-chromeno[2,3-c]pyridin-5-one (3000 mg, 9.66 mmol) in THF (70 mL) was cooled to −30° C. under nitrogen atmosphere. Isopropenylmagnesium bromide, (0.5m solution in THF; 48.3 mL, 24.15 mmol) was added dropwise. The reaction mixture was stirred for 30 min at −30° C. Aqueous saturated ammoniumchloride solution was added, followed by EtOAc. The organic phase was separated and dried over MgSO4. The solvent was removed under reduced pressure to yield the product as a light-yellow solid (3.2 g). The product was taken onto the next reaction step without further purification. Step 2: To a solution of 7-bromo-3-chloro-5-(prop-1-en-2-yl)-5H-chromeno[2,3-c]pyridin-5-ol (3.2 g, 9.08 mmol) in THF (80 mL) was added a solution of borane-THF complex (1.0M in THF; 72.6 mL, 72.6 mmol) at RT under nitrogen atmosphere. The reaction mixture was allowed to stir at RT overnight. Water (10 mL) was added, followed by 2 M NaOH (15 mL). Then hydrogen peroxide (35 wt. % solution in H2O; 22.25 mL, 726 mmol) was added slowly. Et2O was added, followed by water. The organic phase was separated, washed with brine and dried over MgSO4. The solvent was removed under reduced pressure and the residue was purified by flash chromatography (5-30% EtOAc/hexanes). The desired product 7-bromo-3-chloro-5-(1-hydroxypropan-2-yl)-5H-chromeno[2,3-c]pyridin-5-ol (2.53 g, 6.83 mmol, 75% yield) was isolated as a white solid (1:1 mixture of diastereoisomers). Step 3: Azidotrimethylsilane (1.432 mL, 10.79 mmol) and borontriflouride etherate (1.368 mL, 10.79 mmol) were added sequentially to a solution of 7-bromo-3-chloro-5-(1-hydroxypropan-2-yl)-5H-chromeno[2,3-c]pyridin-5-ol (2000 mg, 5.40 mmol) in THF (50 mL). The reaction mixture was heated to 66° C. After 12 h reaction time, additional azidotrimethylsilane (1.432 mL, 10.79 mmol) and borontriflouride etherate (1.368 mL, 10.79 mmol) were added and the reaction mixture was continued to be heated to 65° C. After 24 h reaction time, additional azidotrimethylsilane (1.432 mL, 10.79 mmol) and borontriflouride etherate (1.368 mL, 10.79 mmol) were added and the reaction mixture was continued to be heated to 65° C. After 32 h reaction time, the reaction mixture was cooled to rt and aqueous saturated bicarbonate solution was added carefully, followed by EtOAc. The organic phase was separated and dried over MgSO4. The solvent was removed under reduced pressure and the residue was purified by flash chromatography (10-55% EtOAc/hexanes). 2-(5-azido-7-bromo-3-chloro-5H-chromeno[2,3-c]pyridin-5-yl)propan-1-ol (1.32 g, 85% purity) was isolated of a white solid and taken onto the next step without further purification. Step 4: A solution of 2-(5-azido-7-bromo-3-chloro-5H-chromeno[2,3-c]pyridin-5-yl)propan-1-ol (1300 mg, 3.29 mmol, 85% purity) in THF (10 mL) was cooled to 0° C. under nitrogen atmosphere. LAH (1.0M solution in THF; 3.61 mL, 3.61 mmol) was added dropwise. A mixture of celite and Na2SO4*10H2O was added. The reaction mixture was filtered, the solvent was removed under reduced pressure and the residue was purified by flash chromatography (10-50% EtOAc/hexanes) to afford the desired product 2-(5-amino-7-bromo-3-chloro-5H-chromeno[2,3-c]pyridin-5-yl)propan-1-ol (0.85 g, 2.300 mmol, 70.0% yield) as a white solid. Step 5: To a suspension of 2-(5-amino-7-bromo-3-chloro-5H-chromeno[2,3-c]pyridin-5-yl)propan-1-ol (0.85 g, 2.300 mmol) in EtOH (10 mL) was added anhydrous sodium acetate (0.377 g, 4.60 mmol) followed by the drop wise addition of cyanogen bromide (3.0M in CH2Cl2; 0.920 mL, 2.76 mmol). The suspension was stirred at RT for 48 h. Additional cyanogen bromide (0.8 mL, 0.6 eq) and NaOAc (180 mg, 1.0 eq) were added. The reaction mixture was allowed to stir for 3 days at RT. The reaction mixture was concentrated under reduced pressure, washed with water and extracted with DCM. The combined organic layers were dried over MgSO4 and azeotropically dried with toluene. A white solid was obtained which was suspended in DCM (15 mL). Upon dropwise addition of TFA (2 mL) the reaction mixture turned clear and yellow. The resulting mixture was stirred at RT for 20 min. The solvent was removed under reduced pressure and aqueous saturated NaHCO3 solution and CH2Cl2 were added. The suspension was filtered and 7-bromo-3-chloro-5′-methyl-5′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,4′-[1,3]oxazin]-2′-amine was obtained as a white solid (305 mg). The filtrate was transferred into a separatory funnel. The organic phase was separated and dried over MgSO4. The solvent was removed under reduced pressure and the residue was purfied by flash chromatography to obtain additional 7-bromo-3-chloro-5′-methyl-5′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,4′-[1,3]oxazin]-2′-amine (300 mg).

Provenance & Evidence