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4-bromo-2-chloro-1-trifluoromethoxybenzene[ No CAS ]
[ 95668-21-6 ]
Yield
Reaction Conditions
Operation in experiment
With hydrogen bromide; sodium nitrite; In sulfuric acid; water; acetic acid;
Reference Example 24 A solution of <strong>[64628-73-5]3-chloro4-trifluoromethoxyaniline</strong> (5.1 g) in acetic acid (31 ml) was stirred and treated with sodium nitrite (2.16 g) in concentrated sulphuric acid (14 ml) at below 18 C. After an additional 1 hour at 10 C., the solution was added to a mixture of copper (I) bromide (7.7 g) and hydrobromic acid (24.5 ml) in water at 40-50 C. The reaction was completed by heating at 50 C. for 2 hours, water was added and the mixture filtered. The filtrate was extracted with ether, washed with sodium bicarbonate, dried (magnesium sulphate) and evaporated to give 3-chloro-4-trifluoromethoxy-bromobenzene (6.05 g) as a brown oil, NMR (CDCl3) 7.10(m,1H), 7.35(m,1H), 7.55(d,1H). By proceeding in a similar manner 2-nitro-4-trifluoromethoxy-bromobenzene was prepared, NMR (CDCl3) 7.35(m,1H), 7.75(m,1H), 7.8(d,1H).
With tert.-butylnitrite; In hexane; ethyl acetate; acetonitrile;
(Step 1) Synthesis of 2-bromo-6-fluorobenzothiazole Copper (I) bromide (619 mg, 4.32 mmol) was suspended in acetonitrile (10 ml). To the resulting suspension was added tert-butyl nitrite (640 ael, 5.38 mmol), followed by stirring at 60?C for 5 minutes. To the reaction mixture was added 2-amino-6-fluorobenzothiazole (605 mg, 3.60 mmol). The resulting mixture was stirred at 60?C for 10 minutes. After cooling to the room temperature, the reaction mixture was diluted with ethyl acetate. The ethyl acetate solution was washed with 1N HCl, saturated brine, dried over anhydrous sodium sulfate, and distilled under reduced pressure to remove the solvent. The residue was purified by chromatography on a silica gel column, whereby from n-hexane/ ethyl acetate (5:1, v/v) eluate fractions, 2-bromo-6-fluorobenzothiazole (330 mg, 40%) was obtained as a brown solid. 1H-NMR (CDCl3) delta: 7.19-7.24 (m, 1H), 7.49-7.52 (m, 1H), 7.92-7.96 (m, 1H). MS (ESI) m/z 273.8 (M++1+MeCN).
With sodium nitrite; In water; hydrogen bromide;
EXAMPLE 28 [(2-(6-Fluorobenzothiazolyl))carbonyl]-1-piperidinecarboxylic acid, 1,1-dimethylethyl ester STR36 Slurry 2-amino-6-fluorobenzothiazole (0.255 mol) in water (325 mL), heat to reflux and add 48% hydrobromic acid (130 mL). Maintain at reflux for 20 minutes, cool to 0 C. and add a solution of sodium nitrite (17.56 g, 0.255 mol) water (90 mL), maintaining a temperature of 0 C. Stir at 0 C. for 15 minutes and add by dropwise addition (while keeping cold) to a rapidly stirring mixture of copper (I) bromide (42.03 g, 0.293 mol) in 48% hydrobromic acid (86 mL) and water (225 mL). Stir at room temperature for 20 minutes. Allow to stand overnight, extract into methylene chloride and dry (MgSO4). Evaporate the solvent in vacuo and purify by chromatography to give 2-bromo-6-fluorobenzothiazole.
General procedure: Prepared as described for 1 except CuBr (0.29g, 2.0mmol) and HBr (47%) were used. Yield: 0.25g (27%). Anal. Calcd for C4H7N3IOCuBr2 (MW=463.48): C, 10.37; H, 1.52; N, 9.07. Found: C, 10.28; H, 1.66; N, 8.91. FT-IR (cm-1): 3163(w), 2348(m), 1673(m), 1604(m), 1363(w), 1220(s), 868(s), 664(s). The color of crystal is purple.
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