Potassium Carbonate → (S)-2'-amino-3-p-tolyl-5'H-spiro[chromeno[2,3-b]pyridine-5,4'-oxazol]-7-ol

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Reaction Steps

A vial was charged (S)-2′-amino-3-bromo-5′H-spiro[chromeno[2,3-b]pyridine-5,4′-oxazol]-7-ol (282 mg, 0.809 mmol), p-tolylboronic acid (220 mg, 1.618 mmol), potassium carbonate (559 mg, 4.04 mmol), Pd(PPh3)4 (46.7 mg, 0.040 mmol). The vial was flushed with Ar (g), then Dioxane (4044 μL) and water (2 mL) were added in sequence. The vial was sealed and placed in an 80° C. oil bath. After stirring for 50 minutes, the mixture was partitioned between brine and 10% iPrOH/EtOAc. The layers were separated, and the aq. layer was extracted with EtOAc. The combined organic extracts were dried over sodium sulfate, filtered, and evaporated. The residue was chomatographed on an 80-g Redi-Sep column, eluting with 0-80% of a 90:10:1 mix of DCM/MeOH/NH4OH in DCM to give (S)-2′-amino-3-p-tolyl-5′H-spiro[chromeno[2,3-b]pyridine-5,4′-oxazol]-7-ol (259.36 mg, 0.722 mmol, 89% yield) as an orange solid. Step 2: A 25-mL flask was charged with (S)-2′-amino-3-p-tolyl-5′H-spiro[chromeno[2,3-b]pyridine-5,4′-oxazol]-7-ol (259.36 mg, 0.722 mmol) in DCM (7217 μL) to give an clear, orange solution. triethylamine (201 μL, 1.443 mmol) and 1,1,1-trifluoro-N-phenyl-N-(trifluoromethylsulfonyl)methanesulfonamide (271 mg, 0.758 mmol) were added in sequence. The mixture was stirred for 4 hours before being loaded directly onto a 25-g silica gel loading column with the aid of DCM. The column was eluted onto a prequilibrated 40-g Redi-Sep column with 0-5% MeOH/DCM to give (S)-2′-amino-3-p-tolyl-5′H-spiro[chromeno[2,3-b]pyridine-5,4′-oxazole]-7-yl trifluoromethanesulfonate (317.34 mg, 0.646 mmol, 89% yield) as a cream-colored solid Step 3: A vial was charged with (S)-2′-amino-3-p-tolyl-5′H-spiro[chromeno[2,3-b]pyridine-5,4′-oxazole]-7-yl trifluoromethanesulfonate (45.0 mg, 0.092 mmol), 2-fluoropyridin-3-ylboronic acid (38.7 mg, 0.275 mmol), potassium carbonate (229 μL, 0.458 mmol), and Pd(PPh3)4 (5.29 mg, 4.58 μmol). The vial was flushed with Ar (g), then dioxane (458 μL) (actual amount as 1 mL) and water (0.5 mL) were added in sequence. The vial was selaed and placed in an 80° C. oil bath for 2 hours. The mixture was diluted with EtOAc, washed with brine, dried over sodium sulfate, filtered, and evaporated. The residue was chromatographed on a 12-g Redi-Sep column with 0-5% MeOH/DCM to give (S)-7-(2-fluoropyridin-3-yl)-3-p-tolyl-5′H-spiro[chromeno[2,3-b]pyridine-5,4′-oxazol]-2′-amine (29.53 mg, 0.067 mmol, 73.6% yield) as a tan solid.

Provenance & Evidence