Yield: 99.7%

Reaction Conditions:

with dihydrogen peroxide;trifluoroacetic acid at 60; under 3750.38 Torr;Temperature;

Steps:

2.B Preparation of 3,5-dibromopyridine-N-oxide:
The reactor temperature was raised to 65 ° C, Pressure set to 0.5MPa, Using two pumps with a flow rate of 1-200 ml / min, the reaction liquid I and the reaction liquid II were added to the microreactor, The flow rate of the reaction liquid I was set to 75 ml / min, The reaction solution II flow rate set 58.8ml / min, Which 3,5-dibromo pyridine and hydrogen peroxide molar ratio of 1:2.5, 30s later, The reaction solution flows out of the microreactor, Collected in the tank, Continue feeding until all material is consumed. Isolation and Purification: To the reaction mixture was added 500 ml of ice water, And stirred for ten minutes, filter, Obtained as an off-white solid, 840 ml ice-washed twice to pH = 7,dry, There was obtained 367.8 g of 3,5-dibromopyridine-N-oxide, Purity 99.7% The yield was 98.9%_Step A: Reaction solution I: Take 3,5-dibromopyridine (348g, 1.47mol) was added to a 1L four-necked flask, Temperature control 20-25 deg C, 348ml of trifluoroacetic acid was added, Stir well Measure the volume of 482ml, Molar concentration of 3.05mol / L; Reaction solution II: 30% hydrogen peroxide (416.2 g, 3.67 mol), The concentration of 9.77mol / L.

References:

Aisite (Chengdu) Bio-pharmaceutical Co., Ltd.;Chen Xing;Zeng Tao;Wei Genghui;Guo Peng CN104447531, 2017, B Location in patent:Paragraph 0038; 0039; 0040; 0041; 0042; 0043; 0044-0061