Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF TRIPHENYL PHOSPHINE

Abstract

An improved process for the preparation of triphenyl phosphine The present invention relates to an improved process for the preparation of triphenyl phosphine (TPP). More particularly the present invention relates to an improved process for the preparation of triphenyl phosphine from triphenyl phosphine oxide(TPPO) in non¬aqueous medium by an electrochemical method. The novelty of the present invention lies in the electrochemical preparation of triphenyl phospine in an non aqueous medium which results in the preparation of triphenyl phospine in high yield and make this process simple and eco-friendly with no problem of effluent disposal.

Full Text

The present invention relates to an improved process for the preparation of triphenyl phosphine (TPP). More particularly the present invention relates to an improved process for the preparation of triphenyl phosphine from triphenyl phosphine oxide(TPPO) in non-aqueous medium by an electrochemical method. TPP has the greatest industrial importance of all the tertiary phosphines as a ligand in homogeneous catalysis such as hydroformylation, hydrogenation, oligomerisation, and as a starting material in the synthesis of Vitamin_-A and in the production of fl-carotene. TPP's wide-ranging bonding ability to acceptors such as metals, enables it to be used as ligand in the construction of catalysts. In addition TPP is one of the widely used reagents in general organic transformations such as, conversion of azide to amine, am me to isothiocyanate, alcohol to the corresponding bromides by using PPrij/CBfy. Triphenylphosphine (TPP) is used as an important catalyst ligand and as an intermediate in the synthesis of Wittig reagents, which is produced by BASF in a reaction analogus to Wurtx reaction [H. Muller and A.Stubinger, BASF, DE 2050095, 1970]. TPP is also produced from benzene and phosphorus trichloride in the presence of aluminium chloride. Stochiometric amount of A1CU are generally required because of the complexation of phosphorus compounds [F. Basolo and R.G. Pearson, Mechanism of Inorganic Reactions, 2nd ed,, Jhon Willey & Sons, Inc., New York, 1967]. Hitherto triphenylphospine has been prepared by the reduction of triphenylphosphinc oxide. Conversion of triphenylphosphine oxide, a less valued chemical into a mure value added product triphenylphospine, in a cost-effective way, is an important problem faced by the chemical industry. There are several chemical methods available in literature for this conversion. Some of the reagents used for these conversions are a) 1 ISiCh or SijCU [K. Naumann, G. Zen and K. Mislow, J. Am. Chem. Soc., 91 (1969) 7012,Alkaline hydrolysis of the reaction mixture is necessary to liberate phosphine. b) LiAihU or one of its derivatives [T. Imamoto, T. Takeyama and T. Kusumoto, Chem. I ,ett, (1985) 1491.], Alane in THF [S. Griffin, L. Heath and P. Wyatt, Tetrahedron Lett., 39 (1998) 4405] was reported as a reagent to reduce phosphine oxides to phosphine, which is easy to perform and very high yielding which does not require an aqueous workup. But a solution of alane in THF was prepared by the method of Brown and Yoon [S. Griffin, L. Heath and P. Wyatt, Tetrahedron Lett., 39 (1998) 4405] by adding concentrated H2S04 to a solution of LiAlH4 in THF, which may lead to explosioa These methods have drawbacks of one kind or another. Some common problems are a) not economical in industrial view point, b) the reagents used are hazardous and difficult to handle, c) In most of the cases TPPO is regenerated during aqueous work up and hence the yield is affected. Only few electrochemical methods are reported for the preparation of triphenyl phospine. The available methods are i. Electrochemical synthesis of tertiary phophines from organohalides and chlorophosphines.( J.M.Saveant and S.K.Binh, J.Electroanal.chem..27(1978). ii. Electrochemical deoxygenation of triphenylphosphine oxide.( V.V.Yanilkin, V.S.Gromakov and F.F.Nigmadzyanov, Russian chemical Bulletin, 45(1996)1257. In the above electrochemical methods costly hazardous reagent were used and also gives low yield and conversion for the preparation of triphenyl phosphine . The present electrochemical method avoids the use of costly hazardous reagent and also gives better efficiency for the preparation of triphenyl phosphine. The main object of the present invention is to provide an improved process for the preparation of tripuwiyl phosphine from triphenyl phosphine oxide by an electrochemical method. Another object is to provide an improved process for the preparation of triphenyl phosphine from triphenyl phosphine oxide by an electrochemical method in non aqueous medium. Accordingly the present invention provides an improved process for the preparation of \\\ comprises: preparing an electrolyte by adding 10-25 m mol anhydrous aluminum chloride in a mixture of acetonitrile and benzene having acetonitrile to benzene ratio in the range of 1.9:1 to 2:1.2, adding triphenyl oxide to the above said electrolyte and taking the above said mixture in an undivided electrochemical cell having two electrode system containing an aluminium, anode and a cathode selected from the group consisting of graphite, platinum and zinc, electrochemically reducing triphenyl phosphine oxide under a constant current, at a current density of 30 to 130 A/cm2, at a cell voltage of 6-9V and at a temperature of 50to 90 °C to obtain the desired product. In an embodiment of the present invention the cathode used is selected from the group consisting of graphite, platinum and zinc. In an another embodiment the anode used is aluminium. In yet another embodiment the acetonitrile to benzene ratio used in acetonitrile and benzene mixture is preferably 2:1. In yet another embodiment the current density used for electrolysis is preferably in the range of 60-130 mA/cm2. In still another embodiment the temperature used in electrolysis is preferably in the range of55-80°C. Novelty of the present invention lies in the electrochemical preparation of triphenyl phospine in an non aqueous medium which results in the preparation of triphenyl phospine in high yield and make this process simple and eco-friendly with no problem of effluent disposal. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the invention. General method for the preparation of triphenyl phosphine A mixture of acetonitrile and benzene in a ratio of 1:1 is prepared. Anhydrous aluminium chloride is added to the above said mixture to prepare an electrolyte. Triphenyl phosphene and the above said electrolyte is taken in an undivided electrochemical cell containing an anode and a cathode. Triphenyl phosphene is electrochemically reduced to obtain triphenyl phosphine at different reaction conditions which are summan/.ed in following examples. (Table Remove) The main advantages of the present invention are 1. Using this system high yield (71 %) can be obtained 2. The solvent system used for the electrolysis is an excellent system with high solubility. 3. The high yield of (60-71%) can be obtained using the aluminium anode and graphite cathode. 4. There is no re-generation of TPPO during electrolysis. 5. The process is simple, ecofriendly and no problem of effluent disposal. We claim: 1. An improved process for the preparation of triphenyl phosphine which comprises: preparing an electrolyte by adding 10-25 m mol anhydrous aluminum chloride in a mixture of acetonitrile and benzene having acetonitrile to benzene ratio in the range of 1.9:1 to 2:1.2, adding triphenyl oxide to the above said electrolyte and taking the above said mixture in an undivided electrochemical cell having two electrode system containing an aluminium, anode and a cathode selected from the group consisting of graphite, platinum and zinc, electrochemically reducing triphenyl phosphine oxide under a constant current, at a current density of 30 to 130 A/cm2, at a cell voltage of 6-9V and at a temperature of 50to 90 °C to obtain the desired product. 2. An improved process as claimed in claim 1, wherein the acetonitrile to benzene ratio used in acetonitrile and benzene mixture is preferably 2:1. 3. An improved process as claimed in claims 1-2, wherein the current density used for electrolysis is preferably in the range of 60-130 mA/cm2 . 4. An improved process as claimed in claim 1-3, wherein the temperature used in electrolysis is preferably in the range of 55 - 80 °C. 5. An improved process for the preparation of triphenyl phosphine, substantially as herein described with reference to the examples.

Documents:

793-DEL-2002-Abstract-(24-09-2008).pdf

793-del-2002-abstract.pdf

793-DEL-2002-Claims-(24-09-2008).pdf

793-del-2002-claims.pdf

793-DEL-2002-Correspondence-Others-(24-09-2008).pdf

793-del-2002-correspondence-others.pdf

793-del-2002-correspondence-po.pdf

793-DEL-2002-Description (Complete)-(24-09-2008).pdf

793-del-2002-description (complete).pdf

793-del-2002-form-1.pdf

793-del-2002-form-18.pdf

793-del-2002-form-2.pdf

793-DEL-2002-Form-3-(24-09-2008).pdf

793-del-2002-form-3.pdf