| 62% |
With phosphorus tribromide; In diethyl ether; at 20℃; for 1h; |
EXAMPLE 474-((6-(2-(2,4-Difluorophenyl)-l,l-difluoro-2-hydroxy-3-(lH-tetrazol-l- yl)propyl)pyridin-3-yl)methoxy)benzonitrile (79) and 4-((6-(2-(2,4-difluorophenyl)-l,l- difluoro-2-hydroxy-3-(2H-tetrazol-2-yl)propyl)pyridin-3-yl)methoxy)benzonitrile (80)To a stirred solution of compound J (prepared as in the first step of Example 17; 2.0 g, 10.75 mmol) in CH3OH (30 mL) was added NaBH4 (0.53 g, 13.97 mmol) portionwise at 0 C and the reaction mixture was stirred at 0 C for 1 h. After completion of the reaction (by TLC), CH3OH was removed under reduced pressure, and the reaction mixture was diluted with ice- cold water (75 mL) and extracted with EtOAc (2 x 75 mL). The combined organic layers were washed with water (75 mL) and brine (75 mL), dried over anhydrous Na2S04 and concentrated under reduced pressure to obtain the crude material. Purification by silica gel column chromatography (eluting with 40% EtOAc/hexanes) afforded compound AV (1.4 g, 7.44 mmol, 69%) as a yellow solid. 1H NMR (400 MHz, CDC13): δ 8.35 (s, 1H), 7.59 (dd, J = 8.0, 2.4 Hz, 1H), 7.48 (d, J = 8.0 Hz, 1H), 4.71 (d, J = 6.0 Hz, 2H), 2.03 (t, J = 6.0 Hz, OH). MS (ESI): m/z 188 [M+] .To a stirred solution of compound AV (1.0 g, 5.31 mmol) in Et20 (20 mL) was added phosphorus tribromide (PBr3; 1.5 mL, 15.95 mmol) at 0 C, and the mixture was stirred for 1 h at RT. After complete consumption of the starting material (by TLC), the reaction mixture was quenched with ice-cold water (30 mL), adjusted to pH~8 using satd NaHC03 and extracted with EtOAc (2 x 100 mL). The combined orgainc extracts were washed with water (100 mL) and brine (100 mL), dried over anhydrous Na2S04 and concentrated under reduced pressure to obtain the crude material. Purification by silica gel column chromatography (10% EtOAc/hexanes) afforded compound AW (0.83 g, 3.30 mmol, 62%) as a colorless liquid. 1H NMR (400 MHz, CDC13): δ 8.38 (d, J = 2.4 Hz, 1H), 7.59 (dd, J = 8.0, 2.4 Hz, 1H), 7.48 (d, J = 8.0 Hz, 1H), 4.41 (s, 2H).To a stirred suspension of 4-hydroxybenzonitrile (0.39 g, 3.30 mmol) and Cs2C03 (1.62 g, 4.96 mmol) in DMF (10 mL) was added compound AW (0.83 g, 3.30 mmol) at RT, and the mixture was stirred for 4 h. After completion of the reaction (by TLC), the reaction mixture was quenched with ice-cold water (25 mL) and extracted with EtOAc (4 x 50 mL). The combined organic extracts were washed with water (50 mL) and brine (50 mL), dried over anhydrous Na2S04 and concentrated under reduced pressure to obtain the crude material. Purification by silica gel column chromatography (eluting with 10% EtOAc/hexanes) afforded compound AX (0.90 g, 3.11 mmol, 94%) as a pale yellow solid. 1H NMR (500 MHz, CDC13): δ 8.44 (d, J = 2.0 Hz, 1H), 7.64-7.61 (m, 3H), 7.54 (d, J = 8.5 Hz, 1H), 7.01 (d, J = 8.5 Hz, 2H), 5.08 (s, 2H). MS (ESI): m/z 291 [M+2]+.To a stirred suspension of copper powder (1.55 g, 6.22 mmol) in DMSO (10 mL) was added ethyl 2-bromo-2,2-difluoroacetate (0.63 g, 3.11 mmol) at RT and the mixture was stirred for 1 h. A solution of compound AX (0.9 g, 3.11 mmol) in DMSO (5 mL) was added to the reaction mixture and stirring was continued for another 16 h at RT. After complete consumption of the starting material (by TLC), the reaction mixture was quenched with satd NH4C1 solution (100 mL) and extracted with EtOAc (2 x 100 mL). The combined organic extracts were washed with water (100 mL) and brine (100 mL), dried over anhydrous Na2S04 and concentrated under reduced pressure to obtain the crude material. Purification by silica gel column chromatography (eluting with 25% EtOAc/hexane) afforded compound AY (0.5 g, 1.5 mmol, 49%) as a pale yellow solid. 1H NMR (500 MHz, CDC13): δ 8.71 (s, 1H), 7.94 (d, J = 8.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.63 (d, J = 9.0 Hz, 2H), 7.03 (d, J = 9.0 Hz, 2H), 5.18 (s, 2H), 4.38 (q, J = 7.0 Hz, 2H), 1.34 (t, J = 7.0 Hz, 3H). MS (ESI): m/z 334 [M+2]+.To a stirred solution of l-bromo-2,4-difluorobenzene (348 mg, 1.80 mmol) in Et20 (10 mL) was added w-BuLi (1.6 M in hexane; 0.7 mL, 1.80 mmol) at -78 C, and the mixture was stirred for 30 min under inert atmosphere. A solution of compound AY (500 mg, 1.50 mmol) in Et20 (30 mL) was added to the reaction mixture at -78 C and stirring was continued for another 2 h. After completion of the reaction (by TLC), the reaction mixture was quenched with satd NH4C1 solution (100 mL) and extracted with EtOAc (2 x 100 mL). The combined organic extracts were washed with water (100 mL) and brine (100 mL), dried over anhydrous Na2S04 and concentrated under reduced pressure to afford the crude AZ (1.5 g) as a brownish liquid. This crude material was used in the next step without any further purification. MS (ESI): m/z 401 [M+H]+.To a stirred solution of crude AZ (650 mg, crude) in Et20 (100 mL) was added freshly prepared diazomethane [prepared by dissolving NMU (1.67 g, 16.25 mmol) in a 1 : 1 mixture of 10% KOH solution (100 mL) and Et20 (100 mL) at 0 C followed by separation and drying of the organic layer usin... |
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