FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENS RULES, 2003
PROVISIONAL SPECIFICATION
[See section 10, Rule 13]
PROCESS FOR REGENARATION OF METAL HALIDE SOLUTION AND ITS REUSE IN THE HALOGENATION PROCESS;
DEEPAK NITRITE LIMITED., WHOSE ADDRESS IS CORPORATE OFFICE, DEEPAK COMPLEX, NATIONAL GAMES ROAD, YERAWADA, PUNE - 411 006, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION.
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FIELD OF THE INVENTION
The present invention relates to a process for the regenaration of metal halide solution.
BACKGROUND OF THE INVENTION
Halogenated aromatic compounds find useful applications as precursors / intermediates in the synthesis of pharmaceutical^ important molecules, natural products and specialty performance chemicals. Activated aromatic compounds can be oxidatively brominated using a variety of reagents wherein Br is oxidized to Br + followed by aromatic electrophilic substitution reaction. Reagents comprising of combination of bromide source and oxidizing agents such as Br2 / H202, HBr/ H202, NH4Br- H202/ TBHP in acetic acid, bromine chloride have been reported in the literature.
Journal of Chemical Research, 2004 describes bromination of arenes by using potassium bromide or sodium bromide and concentrated H2SO4. The reaction mixture after heating is extracted with ether and the ethereal extract is washed with saturated sodium bicarbonate solution, water and the solvent is removed to get the crude brominated arene. The reaction mixture is heated at different temperatures. However, this reaction exhibits significant dealkylation and this lowers the yield of brominated compounds.
Organic Process Research and Development, 2004 reports a process for the oxidative bromination of some activated aromatic substrates using dilute aqueous nitric acid and potassium bromide in the presence of a phase transfer catalyst under ambient conditions. The phase transfer catalyst used is tetrabutyl ammonium chloride. The solvent used in the above reaction is dichloroethane. However, the procedure involves, apart from use of PTC, usage and further removal of organic solvent for isolation of desired compound from reaction mass.
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DESCRIPTION OF THE INVENTION
An object of the present invention is to provide an ecofriendly process for the regeneration of metal bromide solution.
Yet another object of the present invention is to reduce the cost of the process as described.
The first aspect of the present invention provides a process to prepare regioselective brominated compounds. The process involves treating aromatic compounds with metal halides optionally with phase transfer catalyst. The aromatic compounds to be brominated are selected from activated substrates such as naphthalene, biphenyls, phenol alkyl ethers, such as anisole, alkylanisole, alkylaryls such as xylene, toluene and other activated aromatic systems. The metal halide is selected from Group I or Group II such as calcium, magnesium, sodium, potassium, or cesium. The solution of metal halide can be acidic, basic or neutral. The reaction temperature is maintained in the range of -5 deg C to 90 deg C. The preferable temperature is around 10 deg C. Nitric acid is then added in the above solution. The reaction is carried out under oxidizing atmosphere by passing oxygen or air. The reaction can also be carried out in an inert atmosphere to form the brominated compound. The brominated compound is separated from aqueous layer by phase separation.
The second aspect of the present invention provides a process to regenerate metal halide, which can be recycled back to the bromination process. The process utilizes the isolated brominated compound formed in the above process for variety of reactions. The use of brominated compounds in various reactions such as Grignard reactions, C-N coupling, C-C coupling, substitution of halogen by hydroxyl, alkoxy or amino group in the presence of alkali generates the corresponding metal halide. The metal halide formed is recycled back to the bromination process without any isolation, purification or pretreatment. One such reaction involves the condensation of aryl bromide to prepare diphenylamine with a known process. Accordingly the reaction of 4-bromo-3-methylanisole with formanilide in the presence of copper, iodine and sodium carbonate gives rise to diphenylformamide and diphenylamine along with the formation of NaBr. The
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aqueous solution of NaBr formed in the above process is recycled back without any pretreatment to the bromination process as a raw material.
The present invention provides an efficient and a simple regioselective method of bromination.
Dated this 17th day of August, 2006.