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ChemicalBook CAS DataBase List 7-Bromo-1H-indazole
53857-58-2

7-Bromo-1H-indazole synthesis

4synthesis methods
1H-INDAZOL-7-AMINE

21443-96-9

7-Bromo-1H-indazole

53857-58-2

The general procedure for the synthesis of 7-bromo-1H-indazole from 7-aminoindazole was as follows: 7-aminoindazole (3.45 g, 25.9 mmol) was dissolved in concentrated hydrobromic acid (25 mL), diluted with water (8.5 mL), and cooled to -10 °C. In another vessel, sodium nitrite (755 mg, 10.9 mmol) was dissolved in water (11.5 mL), cooled and slowly added to the above solution. Subsequently, solid sodium nitrite (1.14 g, 16.5 mmol) was added in batches. The reaction solution was stirred at -5°C for 15 minutes, and then a concentrated hydrobromic acid (11.5 mL) solution of cooled cuprous bromide (3.94 g, 27.5 mmol) was added dropwise over 15 minutes. The reaction mixture was stirred at room temperature for 2 hours and then neutralized with saturated sodium bicarbonate solution. The neutralized mixture was diluted with water (50 mL), filtered and the filter cake was washed with ethyl acetate (300 mL). The filtrate layer was separated and the aqueous layer was extracted with ethyl acetate (3 x 200 mL). The organic layers were combined, dried with anhydrous sodium sulfate and concentrated under reduced pressure to give 7-bromo-1H-indazole (1.88 g, 37% yield).

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Yield:53857-58-2 96%

Reaction Conditions:

with potassium tert-butylate in dimethyl sulfoxide at 20; for 2 h;

Steps:

1.4

A solution of (2-bromo-6-methylphenylazo)-t-butylsulfide (2b; 880 mg, 3.06 mmol) in 10 mL dry DMSO was added dropwise to a solution of potassium t-butoxide (3.44 g, 30.6 mmol) in 25 mL dry DMSO under Ar. The reaction mixture was stirred at room temp for 2 hr, then poured into 150 g ice and 150 mL 2 N HCl solution. The mixture was extracted with ether (2?150 mL). The combined ethereal extracts were washed with brine and dried over MgSO4. Evaporation of the solvent afforded 581 mg (96%) of 3 as a beige solid.

References:

US2004/110815,2004,A1 Location in patent:Page/Page column 19

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