Reaction SMILES: [Br:1][C:2]1[CH:3]=[C:4]2[C:15](=[CH:16][CH:17]=1)[O:14][C:7]1[C:8]([F:13])=[N:9][C:10]([Cl:12])=[CH:11][C:6]=1[C:5]2([CH3:19])O.Cl.O1CCOCC1.C([O-])([O-])=O.[K+].[K+]>C1COCC1>[Br:1][C:2]1[CH:3]=[C:4]2[C:15](=[CH:16][CH:17]=1)[O:14][C:7]1[C:8]([F:13])=[N:9][C:10]([Cl:12])=[CH:11][C:6]=1[C:5]2=[CH2:19]
Reactant: CC1(O)c2cc(Br)ccc2Oc2c1cc(Cl)nc2F
Agent: Cl
Agent: O=C([O-])[O-]
Agent: [K+]
Solvent: C1CCOC1
Solvent: C1COCCO1
Product: C=C1c2cc(Br)ccc2Oc2c1cc(Cl)nc2F
Temperature: 50 °C
Reaction time: 0.5 h
Yield: 69.7 %

Procedure:
A suspension of 7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-one (35 g, 107 mmol) in dry THF (210 mL) under nitrogen atmosphere was cooled to 0° C. and a solution of methylmagnesium bromide (3.0M solution in diethyl ether; 107 mL, 320 mmol) in dry THF (70 mL) was added over 10 minutes via an addition funnel. After complete addition a saturated aqueous solution of NH4Cl (125 mL) was added slowly to the stirring reaction mixture, keeping the internal temperature below 30° C. Water was added and the mixture was extracted twice with EtOAc. The combined organic layers were dried over sodium sulfate before concentrating under reduced pressure to afford 7-bromo-3-chloro-1-fluoro-5-methyl-5H-chromeno[2,3-c]pyridin-5-ol (34.33 g, 100 mmol). Step 2: To a solution of 7-bromo-3-chloro-1-fluoro-5-methyl-5H-chromeno[2,3-c]pyridin-5-ol (50 g, 145 mmol) in THF (300 mL) was added HCl in dioxane (4M, 19.95 mL, 80 mmol). The reaction was heated to 50° C. for 16 hours. The reaction was cooled to RT and K2CO3 (30.1 g, 218 mmol) was added. The reaction mixture was stirred for 30 minutes before filtering. The filtrate was concentrated under reduced pressure and the resulting crude material was washed with DCM. The solid was collected by filtration to afford 7-bromo-3-chloro-1-fluoro-5-methylene-5H-chromeno[2,3-c]pyridine (33.0 g, 101 mmol, 69.6% yield). Step 3: To a solution of 7-bromo-3-chloro-1-fluoro-5-methylene-5H-chromeno[2,3-c]pyridine (33 g, 101 mmol) in THF (450 mL) were added successively water (69.2 mL), iodine (51.3 g, 202 mmol) and silver(II) oxide (46.8 g, 202 mmol) at RT. The reaction mixture was stirred at RT for 10 minutes before adding K2CO3 (41.9 g, 303 mmol). After 30 minutes, the reaction mixture was diluted with EtOAc and filtered through a pad of celite. The filter cake was washed with additional EtOAc. The combined filtrate was concentrated under reduced pressure upon which a white solid precipitated. The solid was filtered off. The filtrate was further concentrated under reduced pressure to obtain a residue which was triturated with ether to afford a white precipitate. The solid was filtered off, combined with the first solid and dried under reduced pressure to afford 7-bromo-3-chloro-1-fluorospiro[chromeno[2,3-c]pyridine-5,2′-oxirane] (23.56 g, 68.8 mmol). Step 4: To a solution of 7-bromo-3-chloro-1-fluorospiro[chromeno[2,3-c]pyridine-5,2′-oxirane] (23.5 g, 68.6 mmol) in DMF (600 mL) was added azidotrimethylsilane (54.6 mL, 412 mmol). The reaction mixture was stirred at RT for 6 hours. Additional azidotrimethylsilane (54.6 mL, 412 mmol) was added and the reaction was stirred at RT for 18 hours. The reaction mixture was diluted with EtOAc and water. The organic layer was separated, washed sequentially with a saturated aqueous LiCl solution and brine before drying over sodium sulfate. The solution was concentrated under reduced pressure to afford (5-azido-7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-yl)methanol (26.12 g, 67.7 mmol, 99% yield). Step 5: A solution of (5-azido-7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-yl)methanol (25.1 g, 65.1 mmol) in THF (500 mL) was cooled to −10° C. and a solution of LAH (1.0 M in THF; 65.1 mL, 65.1 mmol) was added drop wise via an addition funnel over a time period of 1.5 hours. Upon complete addition, the reaction mixture was stirred additional 20 min at −10° C. The reaction mixture was quenched with the drop wise addition of saturated aqueous potassium sodium tartarate solution (60 mL). The reaction was diluted with water and EtOAc. The organic layer was separated, washed with brine and dried over sodium sulfate. The solvent was removed under reduced pressure to afford (5-amino-7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-yl)methanol (21.74 g, 60.5 mmol, 93% yield). Step 6: A 3-neck RBF was charged with (5-amino-7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-yl)methanol (20.7 g, 57.6 mmol) and THF (10 mL). The flask was equipped with two addition funnels which were charged with lithium tert-butoxide solution (1.0M in THF; 98 mL, 98 mmol) and a solution of bromoacetonitrile (6.82 mL, 98 mmol) in THF (10 mL), respectively. The two solutions were added simultaneously to the stirring solution at ambient temperature over a time period of 3 hours. Upon complete addition, the addition funnels were recharged with lithium tert-butoxide solution, 1.0 M in THF (98 mL, 98 mmol) and a solution of bromoacetonitrile (6.82 mL, 98 mmol) in THF (10 mL), respectively. The two solutions were added simultaneously to the stirring solution at ambient temperature over a time period of 3 hours. The reaction was quenched with saturated aqueous ammonium chloride solution and stirred for 16 hours. The reaction was diluted with water and EtOAc. The organic layer was separated and the aqueous layer was extracted twice with EtOAc. The combined organic layers were washed with brine and dried over sodium sulfate. The solution was concentrated under reduced pressure, and the resulting black solid was triturated with ether and filtered to afford a brown precipitate. The filtrate was further concentrated and purified by chromatography (50-100% EtOAc/hexanes). The solids obtained through trituration and purification by chromatography were combined to afford 2-((5-amino-7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-yl)methoxy)acetonitrile (17.9 g, 44.9 mmol). Step 7: A solution of trimethylaluminum solution (2.0 M in toluene; 7.32 ml, 14.64 mmol) was added drop wise to a suspension of 2-((5-amino-7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-yl)methoxy)acetonitrile (3.89 g, 9.76 mmol) in DCE (14.00 ml) at RT under an atmosphere of nitrogen. Upon complete addition, the reaction mixture was heated to 70° C. for 10 minutes. The reaction mixture was cooled to RT quenched with a saturated aqueous potassium sodium tartarate solution. The reaction mixture was vigorously stirred for one hour before diluting with EtOAc and water. The organic layer was separated, and the aqueous layer was washed twice with additional EtOAc. The combined organic layers were washed with brine, dried over sodium sulfate and concentrated under reduced pressure. DCM and EtOAc were added to the residue and the resulting solution was filtered. The filtrate was concentrated under reduced pressure and purified by chromatography (20-70% EtOAc/hexanes) to afford 7-bromo-3-chloro-1-fluoro-2′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,3′-[1,4]oxazin]-5′-amine (Intermediate 7, 1.539 g, 3.86 mmol, 37%). Step 8: Intermediates (R)-7-bromo-3-chloro-1-fluoro-2′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,3′-[1,4]oxazin]-5′-amine (17B) and (S)-7-bromo-3-chloro-1-fluoro-2′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,3′-[1,4]oxazin]-5′-amine (17A) were obtained from racemic 7-bromo-3-chloro-1-fluoro-2′,6′-dihydrospiro[chromeno[2,3-c]pyridine-5,3′-[1,4]oxazin]-5′-amine using similar chiral separation conditions as described herein for intermediate 10.