Title of Invention	"AN IMPROVED PROCESS FOR THE PREPARATION OF DICHLORO THIPHENYL PHOSPHORANE"
Abstract	An improved process for the preparation of dichloro triphenyl phosphorane by reacting triphenylphosphine oxide with diphosgene (trichloromethyl chloroformate) in a mole ratio of 2:1 in an organic solvent medium at a temperature in the range of -10 to 0°C and at ambient pressure conditions and recovering the triphenylphosphorane dichloride by known methods.

Full Text

This invention relates to an improved process for the preparation of dichloro triphenylphosphorane. The present invention particularly relates to the process for the preparation of dichloro triphenylphosphorane commonly known as triphenyIphosphine dichloride, which is obtained by the reaction of diphosgene (trichloromethy1 chloroformate) on tripheny1phosphine oxide in a suitable organic solvent medium and at suitable temperature. Tripheny1phosphine dichloride is an industrially important chemical (Pure & Appl. Chem.,1975,43,527). It is a raw material used for the production of triphenyIphosphine (Ger.Patent, 2,516,361, 1976-Chem.Abst.,1977,86,555B2x; Ger. Patent, 2,638,720, 1977-Chem.Abst.,1977,87,39655p; Jpn. Patent, 78,34,725, 1978-Chem.Abst.,1978,89,109953b; Furo. * Patent, 5,747, 1979-Chem.Abst.,1980,93,114702b; Euro.Pat 5, 746, 1979-Chem.Abst.,1980,93,114703g; Jpn.Patent, 80,149, 294, 1980-Chem.Abst.,1981,94,175258H), which is used in the Wittig synthesis of Vitamin-A. Triphenylphosphine dichloride is used in the manufacture of pesticides (Jpn.Patent, 74,110,650, 1974-Chem.Abst.,1975,82,139691n; Jpn.Patent, 75, 13,536, 1975-Chem.Abst.,1975,83,23459J), as a chlorinating agent (US Patent, 3,715,407, 1 970-Chem.Abst. , 1 973,78, 124244n; Ger.Patent, 2,333,110, 1 973-Chem.Abst. ,1975,82, I56284g), manufacture of carbodiimides (Brit.Patent, 1,252,707, 1969-Chem.Abst.,1973,78,15763k) and as a catalyst in polymerization reactions (Jpn.Patent, 59,223,720, 1984-Chem.Abst.,1985,102,204470n; Eur.Patent, EP 277,907, 1988-Chem.Abst.,1989,11O,8809f) This part describes a brief note on the reported processes of making triphenyIphosphine dichloride: In a patent process (Ger.Patent, 1,192,205, 1965, BASF, Germany) where tripheny1phosphine oxide was taken in a solvent and treated continuously with phosgene gas till the evolution of CO* stopped and then the addition of phosgene was also stopped. Solvent was removed to get solid tri-phenyIphosphine dichloride in about 98* yield. The use of toxic phosgene gas is the limitation to this procedure. Another patent (US Patent, 3,780,111, 1973, Eastman Kodak, USA) deals with it in treating tripheny1phosphine oxide in a suitable solvent with PC1& at a suitable temperature to give tripheny1phopsphine dichloride in 94% yield. Heterogenity and higher reaction temperatures are problematic with this process. Another patent (Jpn.Patent, 80,164,693, 198O, Cobe. Ind.Ltd..Japan) describes the process by treating the tri-phenylphopsphine oxide with carbonmonoxide and chlorine under high pressures and temperatures, yielding tri-phenylphosphine dichloride in 62% yield. Discouraging factor in this process lies in the high pressure and temperature conditions. The above mentioned patented processes have limitations like the use of toxic phosgene gas, high pressure conditions and isolation of pure triphenyIphoephine dichloride. These things leaves an oppurtunity to invent new and alternative processes for the manufacture of tripheny1phosphine dichloride. The objective of the present invention is to develop altogether a new approach, using transportable liquid diphosgene (Merck Index, XI Edition, 1989,p.527,3339; (tricholoromethy1chloroformate), for the preparation of tripheny 1 phosphi ne dichloride. The use of liquid diphosgene has lessen the burden on the lethal toxic effects associated in using the toxic phosgene gas. Liquid diphosgene has the engineering advantage over the toxic gaseous phosgene. Accordingly, the present invention provides an improved process for the preparation of dichloro triphenyl phosphorane which comprises reacting triphenylphosphine oxide with diphosgene (trichIoromethyl chloroformate) in a mole ratio of 2:1 in an organic solvent medium such as herein described at a temperature in the range of -10 to 0°C and at ambient pressure conditions and recovering the triphenylphosphorane dichloride by known methods. The reaction between triphenylphosphine oxide and diphosgene leading to triphenylphosphine dichloride can be conducted very easily in a suitable solvent like dichloromethane/toluene/xylenes/carbontetrachloride/chloroform/etc. at -10° to 0°C to get almost quantitative yield with very high purity of 96%. A variety of solvents can be used for the reaction, but dichloromethane and chloroform were found to be very good. Triphenylphosphine oxide and diphosgene were taken preferably in a mole ratio of 2:1 respectively. At higher temperatures the reaction is highly exothermic and violent, leading to lesser yields and purity with sudden release of gasses. The gas evolved during the reaction is CO2 and can be easily detected using baryta water. A thorough mixing of the reaction medium is essential to control the CO2 gas evolution. Therefore attention must be paid for 5 the thorough stirring of the reaction medium. The liquid diphosgene has the advantage over toxic phosgene gas in mixing and homogeneity of the reaction medium. It is therefore essential to control the reaction temperature and therefore a proper attention must be paid for the heat transfer process involved. Proper rate of addition of diphosgene to triphenylphosphine oxide in dichloromethane medium will also help in the control of heat transfer and also in the evolution of CO gas. Work up involves very 2 simple, stripping off the dichloromethane leaves behind the formed solid triphenylphosphine dichloride in quantitative yield with 96* purity. Thus prepared triphenylphosphine dichloride was assayed by conducting a chemical reaction like benzylalcohol to benzyl chloride. Equimolar mixing of benzylalcohol with triphenylphosphine dichloride in dichloromethane solvent and stirring at room temperature leads to very high yield (94%) of benzylchloride. Thus the reaction conducted, indicates that triphenylphosphine dichloride is formed and can be utilized as chlorinating agent. The process is described in detail in the examples given below which are prescribed by way of illustration only and therefore should not be construed to limit the scope of the invention. 6 Example-1 Diphosgene (5g, 25 mmol) in dichloromethane (10ml) was added dropwise to a solution of TPPO (I3g, 50 mmol) in dichloromethane (15 ml) at 0°C while stirring. Stirring was continued at room temperature for 30 minutes. Removal of dichloromethane from the reaction mixture to give tri-phenyIphosphine dichloride. The yield is 96*, with 96% purity. Example-2 Diphosgene (10g, 50 mmol) in dichloromethane (20 ml) was added dropwise (very slowly) to a solution of TPPO (26g, 100 mmol) in dichloromethane (30 ml) at room temperature while stirring. The reaction is highly exothermic. After the addition of diphosgene, stirring was continued for further 30 minutes. Solvent was removed under vaccum to get tri-pheny1phosphine dichloride. The yield is 96%, with 96* puri ty. We claim: 1. An improved process for the preparation of dichloro triphenyl phosphorane which comprises reacting triphenylphosphine oxide with diphosgene (trichloromethyl chloroform ate) in a mole ratio of 2:1 in an organic solvent medium such as herein described at a temperature in the range of -10 to 0°C and at ambient pressure conditions and recovering the triphenylphosphorane dichloride by known methods. 2. An improved process as claimed in claim 1 wherein organic solvents used are dichloromethane, xylenes, toluene, benzene, carbontetrachloride, chloroform, dichloroethanes, tetrachloroethanes, cyclohexane, chlorocyclohexanes, hexanes, heptanes, octanes. 3. An improved process for the preparation of dichloro triphenyl phosphorane substantially as herein described with reference to the examples.

Documents:

1812-del-1996-abstract.pdf

1812-del-1996-claims.pdf

1812-del-1996-complete specification (granted).pdf

1812-del-1996-correspondence-others.pdf

1812-del-1996-correspondence-po.pdf

1812-DEL-1996-Description (Complete).pdf

1812-del-1996-form-1.pdf

1812-del-1996-form-2.pdf

1812-del-1996-form-4.pdf