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An improved process for the preparation of para-nitrobenzyl bromide

A kind of technology of p-nitrobenzyl bromide and nitrobenzyl bromide, applied in the field of improved preparation of p-nitrobenzyl bromide, can solve problems such as difficulty and no mention of post-processing

Inactive Publication Date: 2012-01-04
COUNCIL OF SCI & IND RES
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the data presented are only for the crude reaction mixture and there is no reference to the work-up of the reaction, which undoubtedly creates serious difficulties if the procedure of this literature is followed

Method used

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  • An improved process for the preparation of para-nitrobenzyl bromide
  • An improved process for the preparation of para-nitrobenzyl bromide
  • An improved process for the preparation of para-nitrobenzyl bromide

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0110] 60 grams (437.9 mmol) of p-nitrotoluene were dissolved in 324 mL of carbon tetrachloride and added to a 1.0 liter capacity glass reactor equipped with an addition funnel and reflux condenser / distillation unit assembly. Add 90 milliliters of brominating agents containing 145.9 mmol of active Br so that during the reaction the ratio of p-nitrotoluene / p-nitrobenzyl bromide ≥ 2: 1, the reaction contents are heated to reflux temperature and with a tungsten wire of 100 watts Lamp external lighting, 7.3 g of 98% H in 30 ml of water 2 SO 4 (72.5 mmole) was added to the addition funnel and the acid was added over 2 hours. (Note: If the color of the reaction mass turns tan, stop adding acid, wait for the color to disappear, and then continue adding acid.) Maintain reflux conditions for an additional 1 hour. The reaction mass was cooled to room temperature, and the organic and aqueous layers were separated. The organic phase was poured into a beaker and kept overnight in the fr...

Embodiment 2

[0116] 0.9 kg (6.57 mol) of para-nitrotoluene was dissolved in 4.8 L of carbon tetrachloride and added to a 10 liter capacity glass reactor equipped with an addition funnel and reflux condenser / distillation unit assembly. Add 1.09L of brominating agent containing 2.18mol active Br so that the ratio of p-nitrotoluene to p-nitrobenzyl bromide ≥ 2:1 during the reaction, the reacted material is heated to reflux temperature and with 3 lamps of 100 watts Tungsten lamp external lighting, 112g in 0.6L water of 98% H 2 SO 4 (1.12 mmol) was added to the addition funnel and the acid was added over 2 hours. (Note: If the color of the reactant changes to tan, stop adding acid, wait for the color to disappear, and then continue adding acid). Reflux conditions were maintained for an additional 1 hour.

[0117] The reaction mass was cooled to about 40°C and the contents were poured into a separation column. The organic phase was poured into a suitable wide-mouth glass container and kept c...

Embodiment 3

[0122] The experiment of Example 2 was repeated, and the stoichiometry of the reagents in each cycle and the yield and purity of the product are shown in Table 3 below. After the 8th cycle, carbon tetrachloride is recovered from the previous mother liquor, and the residue is subjected to vacuum distillation. For this, the residue is first thawed and flushed with nitrogen. Thereafter, the temperature was raised while vacuum was used to distill p-nitrotoluene under reduced pressure [temperature: 140°C (initial)-155°C (final); pressure: 40 mm (initial)-10 mm (final) Hg] . The recovered amount of p-nitrotoluene was 0.514 kg (3.75 mol).

[0123] Note: A small amount of p-nitrobenzyl bromide was also found to distill off. The amount of p-nitrotoluene recovered is subtracted from the total amount of p-nitrotoluene fed for calculating the conversion of p-nitrotoluene. Calculated from the data shown in Table 3 below, the yield of p-nitrobenzyl bromide relative to the p-nitrotoluene...

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Abstract

An improved process for the preparation of p-nitrobenzyl bromide from p-nitrotoluene is disclosed wherein large excess of the reactant in carbon tetrachloride is treated with 2:1 bromide-bromate reagent and the product is isolated efficiently and with high purity through selective cold crystallization from reaction mass so as to allow the mother liquor to be recycled in a subsequent batch without any further work up. The cycles are continued so long as product of desired quality is obtained in adequate yield. Thereafter, the solvent and p-nitrotoluene are recovered from the mother liquor and the residue is treated with sodium borohydride to convert impurities back into reactant or product which is then recycled in the process thereby circumventing the problem of waste disposal and simultaneously yielding the desired product with >95 % yield with respect to p-nitrotoluene and >88 % bromine atom efficiency.

Description

field of invention [0001] The present invention relates to an improved method for preparing p-nitrobenzyl bromide. This compound is widely used in the esterification of carboxylic acids, especially when deprotection is required, such as in analogues of β-lactam antibiotics, analogues of cephalosporins, analogues of penicillin esters, analogues of fusidic acid and Thiomold in the synthesis of analogues. It can also be used as a starting material for the preparation of the drug rizatriptan benzoate. Background technique [0002] Reference is made to the article titled "Bromination of p-nitrotoluene" by J. F. Brewster (J. Am. Chem. Soc; 1918; 40(2); 406-407). Reaction of p-nitrotoluene with liquid bromine in carbon tetrachloride at high temperature (on a hot plate) with exposure to sunlight. The overall yield of p-nitrobenzyl bromide was 71%. The utilization efficiency of bromine atoms was calculated to be 40%. [0003] G.H.Coleman et al. reported a reference preparation m...

Claims

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Application Information

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IPC IPC(8): C07C201/12C07C205/11
CPCC07C201/12C07C205/11C07C201/16C07C205/12
Inventor M·K·阿格拉瓦P·K·戈施M·R·甘迪S·C·乌帕德亚雅S·阿迪穆尔蒂G·拉玛昌德赖拉P·U·帕托利亚G·乔希H·布兰巴特R·J·桑哈维
Owner COUNCIL OF SCI & IND RES
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