ChemicalBook CAS DataBase List 3,5-Dibromo-1H-pyrazole

3,5-Dibromo-1H-pyrazole synthesis

2synthesis methods

Product Name:3,5-Dibromo-1H-pyrazole
CAS Number:67460-86-0
Molecular formula:C3H2Br2N2
Molecular Weight:225.87

The 3,5-dibromo-1H-pyrazole-4-carboxylic acid was treated with trifluorosulfonic anhydride to yield sulphonate, and the bromo-benzene was treated with bromine water, the corresponding Grignard reagent was prepared, then the benzene ring was hydrolyzed, to yield the product 3,5-Dibromo-1H-pyrazole [1].

synthesis of 3,5-Dibromo-1H-pyrazole

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Yield:67460-86-0 86%

Reaction Conditions:

with n-butyllithium in tetrahydrofuran;hexane at -78; for 1 h;

Steps:

1.1 Step 1: 3,5-Dibromo-1 H-pyrazole
To a solution of 3,4,5-tribromo-1H-pyrazole (25 g, 81.96 mmol, 1.0 eq) in THF (300 ml), was added n-BuLi (2.5 M in hexanes, 65.6 ml, 164 mmol, 2.0 eq) over 30 min at -78° C. and the RM was stirred at this temperature for 30 min.
The RM was quenched by the dropwise addition of MeOH-THF (2:3; 125 ml) at -78° C., and stirred for an additional 1.5 h while gradually allowing it to warm to RT.
The solvent was removed under reduced pressure.
The residue was diluted with diethyl ether (600 ml), washed with aq. HCl (0.5 N, 60 ml) and brine (75 ml), dried (Na₂SO₄), filtered and concentrated under reduced pressure to afford the title product (16 g, 86%)

References:

GRÜNENTHAL GMBH;Schunk, Stefan;Reich, Melanie;Koenigs, René Michael US2017/101397, 2017, A1 Location in patent:Paragraph 0202

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1H-Pyrazole-4-carboxylic acid, 3,5-dibromo-

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References