Field of the Invention

The present invention provides an improved process for the preparation of water soluble trivalent iron carbohydrate complexes obtainable from oxidation of maltodextrins using organic hypo halite.

Background of the Invention Iron deficiency anaemia (IDA) is a common haematological complication with potentially serious clinical consequences that may require intravenous iron therapy.

Ferric carboxymaltose (FCM) is a stable, non-dextran iron formulation administered intravenously in large single doses to treat IDA. It is an iron complex that consists of a ferric hydroxide core stabilized by a carbohydrate shell. It is commercially available in the market under the trade name Ferinject®

Ferric carboxymaltose has been designed to provide high iron utilisation and to have a better benefit to risk profile than iron dextran and iron sucrose therapy. In the case of iron dextran, a key risk is the reaction with anti-dextran antibodies leading to the well known dextran induced anaphylactic reactions. In the case of iron sucrose, the negative characteristics include high pH, high osmolarity, low dosage limits and the long duration of administration.

Ferric carboxymaltose allows for controlled delivery of iron within the cells of the reticuloendothelial system and subsequent delivery to the iron-binding proteins ferritin and transferrin, with minimal risk of release of large amounts of ionic iron in the serum.

U.S. Patent No. 3,076,798 discloses, a process for the preparation of iron (III)-polymaltose complex compounds. The iron (III)-polymaltose complex compound preferably has a molecular weight in the range from 20,000 to 500,000 daltons, preferably from 30,000 to 80,000 daltons.

U.S. Patent No. 7,612,109 discloses water-soluble iron carbohydrate complexes (ferric carboxymaltose complexes) obtainable from an aqueous solution of an iron (III) salt, preferably iron (III) chloride, and an aqueous solution of the oxidation product of one or more maltodextrins using an aqueous hypochlorite solution.

PCT application No.WO2011/055374, discloses a process for the preparation of iron (III) carboxymaltose complex using ferric hydroxide.

Even though many prior art processes reported methods for the preparation of Iron (III) carboxymaltose, each process has some limitations with respect to yield, purity and scale-up etc.

Objectives of the Invention

An object of the present invention is to provide an improved process for the preparation of iron carbohydrate complex having weight average molecular weight of 80 kDa to 400 kDa obtainable from oxidation of maltodextrins using organic hypo halite and sodium tungstate and mixtures thereof.

Another object of the present invention is to provide an improved process for the preparation of Ferric carboxymaltose (FCM) obtainable from oxidation of maltodextrins with organic hypohalite in the presence of PTC and sodium tungstate as a catalyst.

Yet, another object of the present invention is to provide an improved process for the preparation of Ferric carboxymaltose (FCM) obtainable from oxidation of maltodextrins with organic hypohalite in the presence of PTC and alkali halide as a catalyst.

In yet another object of the present invention is to provide a process for the preparation of Ferric carboxymaltose (FCM) wherein the oxidation is carried out in solution and safe to handle.

Summary of the invention

Accordingly, the present invention provides an improved process for the preparation of water soluble trivalent iron carbohydrate complex having a weight average molecular weight of 80 kDa to 400 kDa obtainable from oxidation of maltodextrins using an organic hypohalite as oxidising agent in the presence of PTC and sodium tungstate as a catalyst and thereafter complex formation with ferric hydroxide or ferric hydroxide maltodextrin complex.

The present invention provides an improved process for the preparation of water soluble iron (III) carbohydrate complex having a weight average molecular weight of 80 kDa to 400 kDa obtainable from oxidation of maltodextrins using an organic hypohalite as oxidising agent in the presence of PTC and alkali halide as a catalyst and thereafter complex formation with ferric hydroxide or ferric hydroxide maltodextrin complex.

The present invention also provides an improved process for the preparation of Ferric carboxymaltose (FCM) which comprises reacting an aqueous solution of Iron (III) salt and an aqueous solution of oxidised maltodextrins wherein the oxidation is carried out using an organic hypohalite as oxidising agent.

Detailed description of the invention

One aspect of the present invention provides an improved process for the preparation of water soluble trivalent iron carbohydrate complex having a weight average molecular weight of 80 kDa to 400 kDa obtainable from oxidation of maltodextrins using an organic hypohalite as oxidising agent in the presence of sodium tungstate as a catalyst, at an alkaline pH, and complex formation with ferric hydroxide or ferric hydroxide maltodextrin complex wherein, when one maltodextrin is present, the maltodextrin has a dextrose equivalent of between 5 and 20, and wherein, when a mixture of more than one maltodextrin is present, the dextrose equivalent of each individual maltodextrin is between 2 and 40, and the dextrose equivalent of the mixture is between 5 and 20.

Another aspect of the present invention is to provide an improved process for the preparation of Ferric carboxymaltose (FCM) which comprises reacting an aqueous solution of Iron (III) salt and aqueous solution of oxidised maltodextrin wherein the oxidation is carried out using an organic hypohalite solution as oxidising agent and a phase transfer catalyst at an alkaline pH in the presence of sodium tungstate as a catalyst.

Yet another aspect of the present invention, is to provide an improved process for the preparation of water soluble iron (III) carbohydrate complex having a weight average molecular weight of 80 kDa to 400 kDa obtainable from oxidation of maltodextrins using an organic hypohalite as oxidising agent in the presence of alkali halide as a catalyst, at an alkaline pH, and complex formation with ferric hydroxide or ferric hydroxide maltodextrin complex wherein, when one maltodextrin is present, the maltodextrin has a dextrose equivalent of between 5 and 20, and wherein, when a mixture of more than one maltodextrin is present, the dextrose equivalent of each individual maltodextrin is between 2 and 40, and the dextrose equivalent of the mixture is between 5 and 20.

Another aspect of the present invention is to provide an improved process for the preparation of Ferric carboxymaltose (FCM) which comprises reacting an aqueous solution of Iron (III) salt and aqueous solution of oxidised maltodextrin wherein the oxidation is carried out using an organic hypohalite solution as oxidising agent and a phase transfer catalyst at an alkaline pH in the presence of alkali halide as a catalyst.

The organic hypohalites [Chem. Rev. 1954, 54(6), 925-958] used for oxidising maltodextrin is selected from an alkyl or aryl or arylalkyl hypohalite, specifically C1-C4 alkyl hypohalites, more specifically, t-butyl hypochlorite.

The oxidation reaction is carried out in the presence of a catalyst such as transition metal catalyst, for example sodium tungstate. Sodium tungstate used in the present invention can be anhydrous, monohydrate, dihydrate or any other variation thereof.

The oxidation reaction is carried out in the presence of a catalyst such as alkali halide catalyst, specifically alkali bromides, for example sodium bromide.

Specifically, the amount of catalyst is kept as low as possible in order to achieve the end product which can easily be purified, and more specifically catalytic amounts are sufficient.

The Phase transfer catalyst used herein is selected from C1-C10 alkyl or aryl or arylalkyl ammonium halides, specifically Aliquat 336 (methyl trioctylammonium chloride), or mixtures thereof.

Aqueous solution of Iron (III) complex of the present invention used as starting material is ferric hydroxide or polymeric ferric hydroxide maltodextrin complex.

In a preferred embodiment, the process for the preparation of Ferric carboxymaltose (FCM) according to the present invention comprises:
a) treating ferric chloride with aqueous sodium hydroxide to prepare ferric hydroxide,
b) reacting the freshly prepared step-(a) ferric hydroxide with maltodextrin and organic hypohalite in the presence of a catalyst and a PTC at alkaline pH to give Ferric carboxymaltose.

Preferably, a freshly prepared ferric hydroxide is used in step-(b).

Yet another preferred embodiment, the process for the preparation of Ferric carboxymaltose (FCM) according to the present invention comprises:
a) treating ferric chloride with aqueous sodium hydroxide and maltodextrin to prepare ferric hydroxide maltodextrin complex,
b) reacting ferric hydroxide maltodextrin complex prepared in step-(a) with maltodextrin, organic hypohalite in the presence of a catalyst and a PTC to give Ferric carboxymaltose.

In yet another preferred embodiment, the process for the preparation of Ferric carboxymaltose (FCM) according to the present invention comprises:
a) oxidising maltodextrin with an organic hypohalite in the presence of a catalyst and a PTC at alkaline pH to prepare oxidised maltodextrin solution,
b) reacting oxidised maltodextrin solution prepared in step-(a) with aqueous ferric chloride and aqueous sodium carbonate and aqueous sodium hydroxide to give Ferric carboxymaltose.

According to preferable aspect, the present invention is to provide an improved process for the preparation of Ferric carboxymaltose (FCM) which comprises:
a) oxidizing at least one maltodextrin at a pH in the range of 9 to 12 and at a temperature in the range of 0 to 40°C, with /-butyl hypochlorite to form an oxidized maltodextrin solution,
b) contacting the oxidized maltodextrin solution with an aqueous solution of an iron (III) hydroxide complex,
c) raising the pH of the oxidized maltodextrin solution and iron (III) hydroxide complex to a value in the range of 9 to 12,
d) lowering the pH of the oxidized maltodextrin solution and iron (III) hydroxide complex to a value in the range of 4 to 6 and
e) isolating Ferric carboxymaltose (FCM) by adding alcohol to the aqueous complex solution.

To prepare the complex of the invention, the obtained oxidized maltodextrins are reacted with ferric hydroxide. In order to do so, the oxidized maltodextrins can be isolated and re-dissolved. It is also possible to use the obtained aqueous solutions of the oxidized maltodextrins directly for further reaction with ferric hydroxide. For instance, the aqueous solution of the oxidized maltodextrin can be mixed with ferric hydroxide in order to carry out the reaction.

The oxidation may be carried out in an alkali solution, for example at a pH of 9 to 12. The oxidation may be carried out at temperatures in the range of 0 to 40°C, preferably of 15 to 30°C. The reaction may be carried out for a period of 10 minutes to 3 hours, e.g. 30 minutes to 1 hour.

The aqueous solution of the oxidized maltodextrin can be mixed with an aqueous solution of the iron (III) salt in order to carry out the reaction. It is preferred to proceed in a manner so that during and immediately after mixing of the oxidized maltodextrin and the iron (III) salt, the pH is acidic and adjusted to an alkaline pH to a value in the range of 9 to 12, preferably 10 to 11, and maintaining the reaction at a temperature of 25 to 60°C, preferably 50 to 55°C.

During the oxidation, pH is initially maintained at 1 to 3 and at a temperature of 0 to 50°C, followed by adjusting the pH between 9 to 12 with an aqueous alkali hydroxide, preferably sodium hydroxide and maintaining the reaction at a temperature of 25 to 45 °C, preferably 25 to 30°C. Later, the pH can be adjusted to 5 to 6, preferably 5.5, by the addition of aqueous hydrochloric acid and maintaining the reaction at a temperature of 35 to 125 °C, preferably 50 to 100°C.

The following examples describes the nature of the invention and are given only for the purpose of illustrating the present invention in more detail and are not limitative and relate to solutions which have been particularly effective on a bench scale.

Preparation of trivalent iron carboxymaltose:
Example-1:
25grams of maltodextrin (13-17 dextrose equivalents) was dissolved in 75ml of purified water and the mixture was stirred for 10 minutes at RT. To this mixture 3.4gm of Aliquat 336 and 0.05gm of Na2WO4.2H2O were added at room temperature. 30% NaOH solution was added to adjust the pH to 10 to 10.5 and 7gm of tert-butyl hypochlorite (55 to 60 wt. % active chlorine) was added drop wise at 25-30°C while maintaining the pH at 9.5 to 10.5 by adding 30% NaOH solution simultaneously. The reaction mixture was stirred for 1 hour at 25-30°C and pH at 10 and then 40% NaOH solution (4.4ml) was added drop wise to the reaction mass at 25-30°C. To the above reaction mass, iron (III) chloride solution (30.66gm of FeCl3 dissolved in 57.5ml of purified water) was added drop wise over a period of 20 minutes at 25-30°C and stirred for 15 minutes. Aqueous sodium carbonate solution (24gm of Na2CO3 dissolved in 115ml of purified water) was added drop wise at 25-30°C and then 40% NaOH solution was added to establish a pH of 10.5 to 11 and the mixture was heated to 50°C, stirred for 30 minutes. Then the mixture was acidified to pH 5.5 with hydrochloric acid addition and the solution was kept at 50°C for another 30 minutes. Further temperature was raised to 95-100°C and stirred for half an hour at pH 5.5. The reaction mixture was allowed to cool to room temperature and filtered through a celite pad. Then the iron (III) complex was isolated by precipitating with ethanol addition drop wise at room temperature. The obtained brown solid was dried under vacuum at 50°C for 2-3 hours.

Molecular weight = 202 kDa Iron content = 25.65%) w/w

Example-2: Step (i)
28 grams of anhydrous iron (III) chloride was dissolved in 50ml of purified water at room temperature for 10 min stirring. The obtained brownish-yellow clear solution was cooled to 0-5°C and the pH was adjusted to 7.0 by adding aqueous sodium hydroxide solution (21gm of NaOH dissolved in 105 ml of purified water). A brown colour precipitate obtained was maintained for 1 hour at 0-5°C and collected through filtration. The cake was suck dried and used for next step.

Step (ii)
25grams of maltodextrin (13-17 dextrose equivalents) was dissolved in 60ml of purified water and the mixture was stirred for l0min at RT. To this 20% NaOH solution was added to adjust the pH to 10 and followed by 0.1 gm of Na2WO4.2H2O at room temperature over a period of 15 minutes. 3.3gm of tert-butyl hypochlorite was added drop wise at 25-30°C and maintained RM pH at 10 by adding 20% NaOH solution simultaneously. The reaction mixture was stirred for 1 hour at 25-30°C and pH at 10.

At 25-30°C, wet cake of step (i) was added and stirred for 10 minutes. 20% NaOH solution was added drop wise to adjust the reaction mass pH to 10-11 and the slurry was heated to 50°C, stirred for 30 minutes (added 20% NaOH solution to maintain the alkaline pH). Then the solution was acidified to pH 5.5 with hydrochloric acid addition and the solution was kept at 50°C for another 30 minutes. Further temperature was raised to 95-100°C and stirred for half an hour at pH 5.5. The reaction mixture was allowed to cool to room temperature, adjusted pH to 6.0 with 20% NaOH solution and filtered through a celite pad. Then the iron (III) complex was isolated by precipitating with ethanol addition drop wise at room temperature. The obtained brown solid was dried under vacuum at 50°C for 2-3 hours.

Molecular weight = 284 kDa Iron content = 21.65% w/w

Example-3: Step (i)
28 grams of anhydrous iron (III) chloride was dissolved in 50ml of purified water at room temperature for 10 minutes stirring. To this 2gm of maltodextrin (13-17 dextrose equivalents) was added and stirred for 10 minutes at room temperature. The obtained brownish-yellow clear solution was cooled to 0-5 °C and the pH of the reaction mixture was adjusted to 7.0 by adding 20% aqueous sodium hydroxide solution. A brown colour precipitate obtained was maintained for 1 hour at 0-5°C and collected through filtration. The cake was suck dried and used for next step.

Step (ii)
25grams of maltodextrin (13-17 dextrose equivalents) was dissolved in 60ml of purified water and the mixture was stirred for 10 minutes at room temperature. To this 20% NaOH solution was added to adjust the pH to 10 and followed by 0.1 gm of Na2WO4.2H20 at RT. 6gm of tert-butyl hypochlorite was added drop wise at 25-30°C and maintained RM pH at 10 by adding 20% NaOH solution simultaneously. The reaction mixture was stirred for 1 hour at 25-30°C and pH at 10.

At 25-30°C, wet cake of step (i) was added and stirred for 10 minutes. 20% NaOH solution was added drop wise to adjust the reaction mass pH to 10 to 11 and the slurry was heated to 50°C, stirred for 30 minutes (added 20% NaOH solution to maintain the alkaline pH). Then the solution was acidified to pH 5.5 with hydrochloric acid addition and the solution was kept at 50°C for another 30 minutes. Further temperature was raised to 95-100°C and stirred for half an hour at pH 5.5. The reaction mixture was allowed to cool to room temperature, adjusted pH to 6.0 with 20%) NaOH solution and filtered through a celite pad. Then the iron (III) complex was isolated by precipitating with ethanol addition drop wise at room temperature. The obtained brown amorphous solid was dried under vacuum at 50°C for 2-3 hours.

Molecular weight =156 kDa Iron content = 21.13 % w/w

Example-4:
25grams of maltodextrin (13-17 dextrose equivalents) was dissolved in 75ml of purified water and the mixture was stirred for 10 minutes at RT. To this mixture 3.4gm of Aliquat 336 and 0.175gm of NaBr were added at room temperature. 30% NaOH solution was added to adjust the pH to 10 to 10.5 and 6.5gm of tert-butyl hypochlorite (55 to 60 wt. % active chlorine) was added drop wise at 25-30°C while maintaining the pH at 9.5 to 10.5 by adding 30% NaOH solution simultaneously. The reaction mixture was stirred for 30 minutes at 25-30°C and pH at 10 and then 40% NaOH solution (4.4ml) was added drop wise to the reaction mass at 25-30°C. To the above reaction mass, iron (III) chloride solution (30.66gm of FeCl3 dissolved in 57.5ml of purified water) was added drop wise over a period of 20 minutes at 25-30°C and stirred for 15 minutes. Aqueous sodium carbonate solution (24gm of Na2CO3 dissolved in 115ml of purified water) was added drop wise at 25-30°C and then 40% NaOH solution was added to establish a pH of 10.5 to 11 and the mixture was heated to 50°C, stirred for 30 minutes. Then the mixture was acidified to pH 5.5 with hydrochloric acid addition and the solution was kept at 50°C for another 30 minutes. Further temperature was raised to 95-100°C and stirred for half an hour at pH 5.5. The reaction mixture was allowed to cool to room temperature and filtered through a celite pad. Then the iron (III) complex was isolated by precipitating with ethanol addition drop wise at room temperature. The obtained brown solid was dried under vacuum at 50°C for 2-3 hours.

Molecular weight =164 kDa Iron content = 25.05% w/w
ExampIe-5: .

Step (i)
28 grams of anhydrous iron (III) chloride was dissolved in 50ml of purified water at room temperature for 10 min stirring. The obtained brownish-yellow clear solution was cooled to 0-5°C and the pH was adjusted to 7.0 by adding aqueous sodium hydroxide solution (21gm of NaOH dissolved in 105 ml of purified water). A brown colour precipitate obtained was maintained for 1 hour at 0-5°C and collected through filtration. The cake was suck dried and used for next step.

Step (ii)
25grams of maltodextrin (13-17 dextrose equivalents) was dissolved in 60ml of purified water and the mixture was stirred for l0min at RT. To this 20% NaOH solution was added to adjust the pH to 10 and followed by 3.4gm of Aliquat 336 and 0.175gm of NaBr at room temperature over a period of 15 minutes. 7gm of tert-butyl hypochlorite was added drop wise at 25-30°C and maintained RM pH at 10 by adding 20% NaOH solution simultaneously. The reaction mixture was stirred for 1 hour at 25-30°C and pH at l0.

At 25-30°C, wet cake of step (i) was added and stirred for 10 minutes. 20% NaOH solution was added drop wise to adjust the reaction mass pH to 10-11 and the slurry was heated to 50°C, stirred for 30 minutes (added 20% NaOH solution to maintain the alkaline pH). Then the solution was acidified to pH 5.5 with hydrochloric acid addition and the solution was kept at 50°C for another 30 minutes. Further temperature was raised to 95-100°C and stirred for half an hour at pH 5.5. The reaction mixture was allowed to cool to room temperature, adjusted pH to 6.0 with 20% NaOH solution and filtered through a celite pad. Then the iron (III) complex was isolated by precipitating with ethanol addition drop wise at room temperature. The obtained brown solid was dried under vacuum at 50°C for 2-3 hours.

Molecular weight =177 kDa Iron content = 25.4% w/w

Example-6: Step (i)
28 grams of anhydrous iron (III) chloride was dissolved in 50ml of purified water at room temperature for 10 minutes stirring. To this 2gm of maltodextrin (13-17 dextrose equivalents) was added and stirred for 10 minutes at room temperature. The obtained brownish-yellow clear solution was cooled to 0-5°C and the pH of the reaction mixture was adjusted to 7.0 by adding 20% aqueous sodium hydroxide solution. A brown colour precipitate obtained was maintained for 1 hour at 0-5 °C and collected through filtration. The cake was suck dried and used for next step.

Step (ii)
25grams of maltodextrin (13-17 dextrose equivalents) was dissolved in 60ml of purified water and the mixture was stirred for 10 minutes at room temperature. To this 20% NaOH solution was added to adjust the pH to 10 and followed by 0.2gm of NaBr at RT. 6gm of tert-butyl hypochlorite was added drop wise at 25-30°C and maintained RM pH at 10 by adding 20% NaOH solution simultaneously. The reaction mixture was stirred for 1 hour at 25-30°C and pH at 10.

At 25-30°C, wet cake of step (i) was added and stirred for 10 minutes. 20% NaOH solution was added drop wise to adjust the reaction mass pH to 10 to 11 and the slurry was heated to 50°C, stirred for 30 minutes (added 20% NaOH solution to maintain the alkaline pH). Then the solution was acidified to pH 5.5 with hydrochloric acid addition and the solution was kept at 50°C for another 30 minutes. Further temperature was raised to 95-100°C and stirred for half an hour at pH 5.5. The reaction mixture was allowed to cool to room temperature, adjusted pH to 6.0 with 20% NaOH solution and filtered through a celite pad. Then the iron (III) complex was isolated by precipitating with ethanol addition drop wise at room temperature. The obtained brown amorphous solid was dried under vacuum at 50°C for 2-3 hours.

Molecular weight = 145 kDa
Iron content = 21.66% w/w

We claim:

1. A Process for the preparation of water soluble trivalent iron carbohydrate complex having a weight average molecular weight of 80 kDa to 400 kDa obtainable from oxidation of maltodextrins using organic hypohalite.

2. The process as claimed in claim 1, for the preparation of Ferric carboxymaltose (FCM) which comprises reacting an aqueous solution of iron (III) salt and aqueous solution of oxidised maltodextrin, wherein oxidation is carried out using organic hypo halite as oxidising reagent in presence/absence of transition metal catalyst and PTC.

3. The process as claimed in claim 1, for the preparation of Ferric carboxymaltose (FCM) which comprises reacting an aqueous solution of iron (III) salt and an aqueous solution of oxidised maltodextrin, wherein oxidation is carried out using organic hypo halite as oxidising reagent in presence/absence of alkali halide catalyst and PTC.

4. The process as claimed in claims 1-3, wherein organic hypohalite oxidising agent is selected from alkyl or aryl or arylalkyl hypohalites, specifically C1-C4 alkyl hypohalites.

5. The process as claimed in claim 4, wherein C1-C4 alkyl hypohalites is t-butyl hypochlorite.

6. The process as claimed in claim 2 to 3, wherein the PTC used is selected from C1-C10 alkyl or aryl or arylalkyl ammonium halides, specifically Aliquat 336.

7. The process as claimed in claims 1 to 6, wherein the oxidation is carried out at a pH of 9 to 12, at temperatures in the range of 0 to 50°C.

8. The process as claimed in claims 2 to 7, wherein the transition metal catalyst is sodium tungstate.

9. The process as claimed in claims 2 to 7, wherein the alkali halide catalyst is alkali bromide, specifically sodium bromide.

10. An improved for the preparation of Ferric carboxymaltose (FCM) which comprises:
a) treating ferric chloride with aqueous sodium hydroxide to prepare ferric hydroxide,
b) reacting the ferric hydroxide of step-(a) with maltodextrin and organic hypohalite and in the presence of transition metal catalyst or alkali halide and a PTC to give Ferric carboxyrnaltose.

11. An improved and efficient process for the preparation of Ferric carboxyrnaltose (FCM) which comprises:
a) treating ferric chloride with aqueous sodium hydroxide and maltodextrin to prepare ferric hydroxide maltodextrin complex,
b) reacting ferric hydroxide maltodextrin complex prepared in step-(a) with maltodextrin and organic hypohalite in the presence of transition metal catalyst or alkali halide and a PTC to give Ferric carboxyrnaltose.

12. An improved process for the preparation of Ferric carboxyrnaltose (FCM) which comprises:
a) oxidizing at least one maltodextrin in an aqueous solution at a pH in the range of 9 to 12 and a temperature in the range of 0 to 50°C, with tert-butyl hypochlorite in the presence of transition metal catalyst or alkali halide and a PTC to form an oxidized maltodextrin solution,
b) contacting the oxidized maltodextrin solution with an aqueous solution of an iron (III) salt and
c) raising the pH of the oxidized maltodextrin solution and iron (III) salt solution to a value in the range of 9 to 12
d) lowering the pH of the oxidized maltodextrin solution and iron (III) salt mixture to a value in the range of 4 to 6 and
e) isolating Ferric carboxyrnaltose (FCM) by adding alcohol to the aqueous complex solution.

13. The process as claimed in claims 10 to 12, wherein organic hypohalite oxidising agent is selected from C1-C4 alkyl hypohalite.

14. The process as claimed in claims 10 to 12, wherein C1-C4 alkyl hypohalites is t-butyl hypochlorite.

15. The process as claimed in claims 10 to 12, wherein the transition metal catalyst is sodium tungstate.

16. The process as claimed in claims 10 to 12, wherein the alkali halide catalyst is alkali bromide, specifically sodium bromide.

17. The process as claimed in claims 10 to 12, wherein the PTC used is selected from C1C10lkyl or aryl or arylalkyl ammonium halides, specifically Aliquat 336.