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With sulfuric acid; nitric acid; at 85℃;Cooling with ice;
a) 5-Fluoro-3-nitropyridin-2-ol A mixture of concentrated sulphuric acid (1 mL) and fuming nitric acid (1 mL) was added dropwise to a stirred, cooled (ice-bath) mixture of 5-fluoropyridin-2-ol (1.20 g, 10.6 mmol) and concentrated sulphuric acid (2.7 mL). The mixture was warmed to ambient temperature and then to 85 C. After 2 hours, the mixture was cooled and poured onto ice-water. The precipitate was filtered and dried to give the title compound (0.72 g, 43%) as a yellow solid. LRMS (m/z): 157 (M-1)+. 1H NMR delta (300 MHz, DMSO-d6): 8.28 (s, 1H), 8.67 (s, 1H).
43%
With sulfuric acid; nitric acid; at 85℃; for 2h;Cooling with ice;
5-Fluoro-2-methoxypyridin-3 -amine a) 5-Fluoro-3-nitropyridin-2-olA mixture of concentrated sulphuric acid (1 mL) and fuming nitric acid (1 mL) was added dropwise to a stirred, cooled (ice-bath) mixture of 5-fluoropyridin-2-ol (1 .20 g, 10.6 mmol) and concentrated sulphuric acid (2.7 mL). The mixture was warmed to ambient temperature and then heated to 85 C. After 2 hours, the mixture was cooled and poured onto ice-water. The precipitate was filtered and dried to give the title compound (0.72 g, 43%) as a yellow solid.LRMS (m/z): 157 (M-1 )+.1H NMR delta (300 MHz, DMSO-d6): 8.28 (s, 1 H), 8.67 (s, 1 H).
40%
With sulfuric acid; nitric acid; at 28 - 65℃; for 2.75h;
To a solution of 5-fluoro-2-hydroxypyridine (200 mg, 1.77 mmol) in concentrated sulfuric acid (900 mul) was added, dropwise over 15 minutes, a premixed solution of concentrated sulfuric acid (900 mul) and fuming nitric acid (170 mul). The internal temperature rose by up to 280C. The reaction mixture was then heated at 650C for 2.5 hours. The cooled mixture was poured onto ice-water, and the pH of the mixture was adjusted to 2.5 with sodium carbonate. It was then extracted with ethyl acetate (2 x 25 ml). The aqueous layer was concentrated and extracted again with a mixture of tetrahydrofuran (25 ml) and ethyl acetate (25 ml). The organic layers were combined, dried over magnesium sulfate, filtered and concentrated under reduced pressure to yield the title compound (112 mg, 40%) as a solid. 1H NMR (400MHz, DMSO-D6): delta 8.22 (dd, 1 H), 8.60 (dd, 1 H); LRMS APCI" m/z 157 [M-H]'.
With sulfuric acid; nitric acid; In water; at 65 - 80℃; for 1h;
The solid from above containing (4-80) was divided in 4 batches and treated with H2SO4 and fuming HNO3 as shown below. The amounts used were: Compound 4-80 was dissolved in sulfuric acid (the larger amounts indicated above) at rt and then heated to 65 C. A preformed solution of fuming nitric acid and sulfuric acid (the smaller amount indicated above) was added dropwise. The temperature was kept between 65 C. and 80 C. (rxn is exothermic and although the bath is at 65 C., temperature goes higher, usually 75, sometimes 80 C.). After the addition was complete, the reaction mixture was heated at 65 C. for an additional hr. The reaction mixture was then cooled to rt and poured in a flask containing ice) (20 g of ice/gr compound, evolution of gas occurred). A solid precipitated out and it was collected by filtration (1HNM? showed 4-80 and something else (discarded)). [1493] The aqueous layer was extracted with AcOEt several times (3-5) and concentrated on a rotary evaporator under vacuum to afford a solid that was triturated with ether to afford 5-80 as a bright yellow solid. A total of 117 g of desired product was collected in the first crop (27% yield from diazonium salt). A portion did not crystallize: this oil was triturated with MeOH and Et2O to afford 3.6 g of 5-80; another precipitation from the mother liquid afforded an additional 6.23 g of the desired product 5-80 [1494] Total:117.0+3.6+6.23 =126.83. 30.4%). Yield for 3 steps (decomposition of diazonium salt; deprotection and nitration). [1495] Analytical data from Notebook: 53877-115: 1HNMR(delta, MeOD): 8.56-8.27 (dd, J=7.5, 3.3 Hz, 1H), 8.01 (d, J=3.3 Hz, 1H); LC/MS(M+1)+=158.9; rt=0.15 min. [1496] Note: A portion of the aqueous acidic solution was taken and neutralized with Na2CO3 until effervescence stopped and then it was extracted with AcOEtA different product was obtained. No desired product in these extracts.
With sulfuric acid; nitric acid; at 20 - 80℃; for 1h;
Intermediate 3 was dissolved in sulfuric acid (the larger amounts indicated above) at rt and then heated to 65 C. A preformed solution of fuming nitric acid and sulfuric acid (the smaller amount indicated above) was added dropwise. The temperature was kept between 65 C. and 80 C. (rxn is exothermic and although the bath is at 65 C., temperature goes higher, usually 75, sometimes 80 C.). After the addition was complete, the reaction mixture was heated at 65 C. for an additional hr. The reaction mixture was then cooled to rt and poured in a flask containing ice) (20 g of ice/gr compound, evolution of gas occurred). A solid precipitated out and it was collected by filtration (1HNM? showed intermediate 4 and something else (discarded)). The aqueous layer was extracted with AcOEt several times (3-5) and concentrated on a rotary evaporator under vacuum to afford a solid that was triturated with ether to afford intermediate 4 as a bright yellow solid. A total of 117 g of desired product was collected in the first crop (27% yield from diazonium salt). A portion did not crystallize: this oil was triturated with MeOH and Et2O to afford 3.6 g of intermediate 4; another precipitation from the mother liquid afforded an additional 6.23 g of the desired product intermediate 4. Total: 117.0+3.6+6.23=126.83. 30.4%). Yield for 3 steps (decomposition of diazonium salt; deprotection and nitration). Analytical data from Notebook: 53877-115: 1HNMR(delta, MeOD): 8.56-8.27 (dd, J=7.5, 3.3 Hz, 1H), 8.01 (d, J=3.3 Hz, 1H); LC/MS(M+1)+=158.9; rt=0.15 min.
With sulfuric acid; nitric acid; In water; at 65 - 80℃;
Compound 4-80 was dissolved in sulfuric acid (the larger amounts indicated above) at rt and then heated to 65 C. A preformed solution of fuming nitric acid and sulfuric acid (the smaller amount indicated above) was added dropwise. The temperature was kept between 65 C. and 80 C. (rxn is exothermic and although the bath is at 65 C., temperature goes higher, usually 75, sometimes 80 C.). After the addition was complete, the reaction mixture was heated at 65 C. for an additional hr. The reaction mixture was then cooled to rt and poured in a flask containing ice) (20 g of ice/gr compound, evolution of gas occurred). A solid precipitated out and it was collected by filtration (1HNM showed 4-80 and something else (discarded)). The aqueous layer was extracted with AcOEt several times (3-5) and concentrated on a rotary evaporator under vacuum to afford a solid that was triturated with ether to afford 5-80 as a bright yellow solid. A total of 117 g of desired product was collected in the first crop (27% yield from diazonium salt). A portion did not crystallize: this oil was triturated with MeOH and Et2O to afford 3.6 g of 5-80; another precipitation from the mother liquid afforded an additional 6.23 g of the desired product 5-80. Total: 117.0+3.6+6.23=126.83. 30.4%). Yield for 3 steps (decomposition of diazonium salt; deprotection and nitration). Analytical data from Notebook: 53877-115: 1HNMR(delta, MeOD): 8.56-8.27 (dd, J=7.5, 3.3 Hz, 1H), 8.01 (d, J=3.3 Hz, 1H); LC/MS(M+1)+=158.9; rt=0.15 min. Note: A portion of the aqueous acidic solution was taken and neutralized with Na2CO3 until effervescence stopped and then it was extracted with AcOEt A different product was obtained. No desired product in these extracts.
With sulfuric acid; nitric acid; In water; at 85℃; for 1h;
In Step A, compound zzl' (1.2 g, 0.01 mol) was dissolved in sulfuric acid (2.7 mL) at room temperature. Premixed fuming nitric acid (1 mL) and sulfuric acid was added dropwise at 5-10 C. to the solution of compound zzl'. The reaction mixture was then heated at 85 C. for 1 hour, then was cooled to room temperature and poured into ice (20 g). The yellow solid precipitate was collected by filtration, washed with water and air dried to provide 1.01 g of compound zz2'.
With nitric acid;sulfuric acid;
Intermediate 4,4-fluoro-7-bromo-6-azaindole, was prepared according to the following scheme: [CHEMMOL-00081] [0364] A) fuming HNO3, H2SO4; [0365] B) POBr3/DMF, 110 C.; [0366] C) vinylmagnesium bromide, THF, -78 C. -20 C. [0367] Intermediate 4 was isolated as a brownish solid. MS m/z: (M+H)+ calcd for C7H5BrFN2: 214.96; found 214.97. HPLC retention time: 1.28 minutes (column G).
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