Method of producing ketopantolactone

FIELD: chemistry.

SUBSTANCE: present invention relates to a method of producing ketopantolactone, which is widely used in synthesis of pantothenic acid (vitamin B5), as well as other biologically active substances. The method of producing ketopantolactone involves oxidative dehydrogenation of pantolactone under the action of electrochemically generated bromine from a bromide anion source in an electrolysis cell equipped with an anode, a cathode and a stir-bar in the medium of a chlorine-containing organic solvent in a two-phase system containing an organic and an aqueous layer while passing electrical current of 4-6 F per 1 mole pantolactone and stirring the reaction mass at a rate of 1-4 rps at temperature 35-70C and pH of the medium equal to 0.5-1.5.

EFFECT: simple technology of producing ketopantolactone, avoiding the need to use dangerous (poisonous) and hard to handle molecular bromine, high conversion of the starting pantolactone and high output of the end product which reaches 85%.

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The present invention relates to the field of electrochemistry and chemistry of lactones, ketones and alcohols, particularly to a method of obtaining ketopantolactone formula (I) oxidation of pantolactone formula(II).

The ketopantolactone finds wide application to obtain Pantothenic acid (vitamin B5), as well as other biologically active substances on the basis of calcium Pantothenate, pantethine, pantotenovoi alcohol [S.V. Pansare, R.P. Jain, Enantioselective Synthesis of (S)-(+)-Pantolactone. Organic Letters 2000, 2, 175-177; L. Synoradzki, So Rowicki, M. Wlostowski. Calcium Pantothenate. Part 2.1 Optimisation of Oxynitrilase-Catalysed Asymmetric Hydrocyanation of 3-Hydroxy-2,2-dimethylaldehyde: Synthesis of (R)-Pantolactone. Org. Process Res. Dev., 2006, 10, 103-108; L. Synoradzki, H. Hajmowicz, J. Wisialski, A. Mizerski, T. Rowicki. Calcium Pantothenate. Part 3. Process for the Biologically Active Enantiomer of the Same via Selective Crystallization and Racemization. Org. Process Res. Dev., 2008, 12, 1238-1244; So Rowicki, L. Synoradzki, M. Wlostowski. Calcium Pantothenate. Part 1. (R,S)-Pantolactone Technology Improvement at the Tonnage Scale. Industrial & Engineering Chemistry Research 2006, 45, 1259-1265; R.J. Williams, (2006) The Chemistry and Biochemistry of Pantothenic Acid, in Advances in Enzymology and Related Areas of Molecular Biology, Volume 3 (eds F. F. Nord and C. Werkman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470122488.ch8].

Pantothenic acid is a structural component of one of the key substances of metabolism of coenzyme a, which participates in all major types of protein, lipid and carbohydrate. Pantothenic acid helps to restore the tile is to tissues, treatment and maintenance of skin health. Pantothenic acid ensures the normal functioning of the adrenal cortex and stimulates the synthesis of cortisone, which allows its use in the treatment of most inflammatory and autoimmune diseases. Very important is the ability of Pantothenic acid to normalize lipid metabolism and reduce the level of cholesterol in the blood. The synthesis of vitamin B5 is a multistage: aldonna condensation samalanga aldehyde and formaldehyde, cyanide-acetonecyanohydrin, saponification and lactonization, oxidation of the obtained racemic pantolactone to ketopantolactone, stereoselective hydrogenation of ketopantolactone with obtaining pure biologically active R-isomer of Pantothenic acid.

A method of obtaining ketopantolactone, based on the oxidation of pantolactone system trichloride ruthenium-metaperiodate sodium in a mixture of water-acetic acid ethyl ester under the action of microwave radiation. The output of ketopantolactone is 72%. The method involves the use of expensive ruthenium catalyst and a large mass flow of non-regenerating metaperiodate sodium 145,5 grams / 25.5 grams of pantolactone [Manufacture of ketopantolactone. WO 2003/91235 A1; Inventors: Bonrath, Werner; Reinhard Karge; Nuechter Matthias; Bernd Ondruschka; Applicants: Roche Vitamins AG; Bonrath, Werner; Reinhard Karge; Nuechter Matthias; Bernd Ondruschka].

Know the ten is also a method of obtaining ketopantolactone, based on the oxidation of pantolactone the hypochlorites such as calcium hypochlorite. The ketopantolactone is obtained with a yield of 75%. The method involves the use of large quantities of volatile and toxic calcium hypochlorite 136,9 grams / 65 grams of pantolactone, which after use, do not regenerate [Process for manufacturing a diketone. US 4225506, 1980. Inventor: Max Schmid. Patentee: Hoffmann-La Roche Inc.].

A method of obtaining ketopantolactone, which is taken as a prototype, oxidative dehydrogenation of pantolactone under the action of bromine in chloroform. The output of pantolactone is within 82-85%. The synthesis is carried out in a two-liter flask, load 100 g pantolactone, 960 ml of chloroform, 150 ml of water and 137 g of bromine. The reaction mixture is light 300-watt incandescent, and boil two hours. After the reaction control by TLC, the reaction mixture was transferred into a separating funnel, add 40 ml of water, separate the organic layer, washed with 40 ml of water. Water layers combine (they are a concentrated solution of Hydrobromic acid), extracted with chloroform 230 ml Organic layers are combined chloroform is evaporated; crystallizes the ketopantolactone mass 83,7,

Water fraction containing 127 g Nug and 11.7 g of bromine, film is evaporated at the evaporator, the obtained azeotropic mixture removador the e-water is electrolyzed in a divided cell, using steel anode and a graphite cathode. Electrochemically using an electrolyzer produce bromine in the amount of 88% from the oxidation. The bromine is then again used for the oxidative dehydrogenation of pantolactone [L.V.Kaabak, N..Stepnova, .V.Khudenko, and A.P.Tomilov. Low-Waste Process for Preparing Ketopantolactone, with Electrochemical Recovery of Bromine. Russian Journal of Applied Chemistry, Vol.76, No.8, 2003, pp.1315-1318 (Journal of applied chemistry, t, No.. 8, 2003, str-1354)].

The disadvantage of the prototype is its two-phase process, the application on the first (chemical) stage of molecular bromine, which is poisonous and dangerous technologies oxidant, the use of lighting for carrying out oxidation and the need after carrying out the synthesis and separation of the reaction mixture, in the second stage, the electrochemically regenerating the bromine in the cell with the divided electrochemical cell for re-introduction into the oxidation process.

The present invention is to simplify the technology of ketopantolactone while maintaining a sufficiently high yield of the target product.

This object is achieved, we offer one-step method of obtaining ketopantolactone by oxidative dehydrogenation of pantolactone under the action of bromine in the environment of chlorine-containing organic solvent under heating using electrolysis, sleep is defined by the anode and cathode distinguishing feature of which according to the invention is that the oxidative dehydrogenation of pantolactone carried out under the action of the electrochemically generated bromine from bromide anion in the electrolytic cell, is further provided with a magnetic maslinica, in a two-phase system containing organic and aqueous layers, by passing an electric current equal to 4-6 F 1 mol of pantolactone, and stirring the reaction mass with a speed of 1-4 cycles per second at a temperature of 35-70C and pH of 0.5-1.5.

The yield of the target product reaches 85% at a conversion of 99%.

As the source of the bromide anion using Hydrobromic acid salt, for example sodium or potassium salt.

As the chlorine-containing organic solvent used methylene chloride, chloroform or carbon tetrachloride.

The cell is further provided with a magnetic maslinica with a ratio of length maslinica to the diameter of the cell from 0.5 to 0.2.

The electrolytic cell equipped with an anode made of platinum or graphite, and the cathode is made of titanium or steel.

Oxidation of pantolactone to ketopantolactone carried out in a two-phase system of an organic solvent (methylene chloride, chloroform or carbon tetrachloride) - water (saturated sodium sulfate to vysalivaniya lactones from the aqueous phase).

The entity from whom retene also explains the drawing, which shows the electrolytic cell 1 is supplied with anode 2, cathode 3, a magnetic maslinica 4, and also shows the aqueous layer 5, an interface 6, the organic layer 7, and a diagram of the process of anodic oxidation of bromoiodide 8.

The method of obtaining ketopantolactone is as follows.

Water (70-150 ml) saturated with sodium sulfate (to vysalivaniya lactones from the aqueous phase) to a concentration of from 10 to 30 wt.%, acidified with sulfuric acid to pH=0.5 to 1.5 and added the bromide of potassium (sodium) in the amount of 20-30 g / 100 ml of the aqueous phase, with stirring and dissolved. Then add a solution of pantolactone (5-15 g) in an organic solvent (50-150 ml). At a temperature of 35 to 60C pass a specified amount of electric current (1-5,5 a; 4-6 F/mol), using graphite or platinum anode and a titanium or steel cathode (ranging from 10 to 100 cm; conversion pantolactone controlled by TLC). During the pulses, the mixture is stirred with a magnetic maslinica speeds 1-4 revolutions per second; the ratio of the length of maslinica to the diameter of the reactor is from 0.5 to 0.2. Stirring is carried out so that the lower organic layer is not in contact with the cathode and is not formed emulsion.

In the case of contact between the organic layer and the cathode or the formation of the emulsion will be undesirable processes of recovery of bromide to bromine is hydrogen and ketopantolactone to pantolactone, which will lead to lower output ketopantolactone. After passing an electric current mixture is stirred for further 1 hour to almost complete bleaching mixture. The mixture is separated in the separating funnel, the upper (aqueous) phase is extracted with chloroform 20.25 volume (extracted aqueous phase), the extract is mixed with an organic solvent remaining after the reaction, evaporated on a rotary evaporator at 50-60C under vacuum, the resulting residue is weighed to determine the output.

The process of synthesis of ketopantolactone due to the fact that the electric current oxidizes bromovalerate (obtained from the bromide of potassium or sodium and sulfuric acid) to bromine, the latter in turn oxidizes pantolactone to ketopantolactone, while the regenerated bromovalerate, which again is oxidized by an electric current. Thus is realized the cyclical nature of use of the system bromo - bromovalerate in this oxidation process; filling of oxidizer in the system occurs due to the electric current. The process of recovering bromine from the cathode to the Hydrobromic acid is excluded due to the fact that under slow stirring, no formation of the emulsion and heavy bromine, poorly soluble in water, practically does not reach the cathode, and gets into the organic phase where it is to the oxidizer.

One of the distinguishing features of the invention is the detection of the influence of mixing on the output of ketopantolactone. Generally, in organic synthesis in heterogeneous systems it is recommended that intensive mixing of the two liquid phases to form an emulsion), in the present invention is applied very weak mixing; the lower phase formed waves (inextricably). Not recovering bromine to Hydrobromic acid and ketopantolactone to pantolactone. In the case of intensive mixing complete conversion of pantolactone not achieved.

The technical result of the invention is to simplify the technology of ketopantolactone by creating technologically single-stage process that combines chemical phase oxidative dehydrogenation of pantolactone and electrochemical stage gradual (metered) generate bromine in a reaction medium in one device (the cell). This eliminates, in comparison with the prototype, the need to use dangerous (poisonous) and cumbersome molecular bromine and its electrochemical regenerating in the second stage, and does not require lighting 300 watt incandescent lamp. Thus, the whole process is carried out in one stage in one device (which electrolyzer) without the use of a divided electrochemical cell, while you can obtain the target product with a sufficiently high yield (up to 85%) at high conversion of the original pantolactone (up to 99%).

The invention meets the criterion of "novelty", as known in the scientific-technical and patent literature does not include a full set of features characterizing the present invention. The invention also meets the criterion of "inventive step"as the claimed invention not apparent to the expert in the obvious way from the prior art.

The present invention is industrially applicable as a ketopantolactone finds wide application to obtain Pantothenic acid (vitamin B5), as well as other biologically active substances on the basis of calcium Pantothenate, pantethine, pantotenovoi alcohol.

The invention is illustrated by the following examples without limiting its scope.

Example 1.

In the cell with a volume of 300 ml in 100 ml water dissolve 30 g of sodium sulfate, add sulfuric acid to achieve a pH of 1, add 25 g of sodium bromide. To cooked mixture add a solution of 10 g of pantolactone (0,0769 mol) in 100 ml of chloroform. Dipped in the aqueous phase platinum anode and a steel cathode; the area of the electrodes 10 CSM At a temperature of 55-60C and stirring magnetic maslinica with a speed of 3 revolutions per second making the cabins electric current in the amount of 6 F/ mol of pantolactone. After passing an electric current mixture is stirred for further 1 hour to almost complete bleaching mixture.

The mixture is separated in the separating funnel, the upper (aqueous) phase is extracted with chloroform 20.25 ml, the extract is mixed with an organic solvent remaining after the reaction. The combined organic layers are filtered through a layer of silica gel (50 g) and activated charcoal (30 g), evaporated on a rotary evaporator at 50-60C under a water-jet vacuum pump. The resulting ketopantolactone weight gain of 8.37 g (0,0654 mol, yield 85%).

Analogously to example 1 under different conditions obtained target product. The process conditions, the conversion of pantolactone and the output of ketopantolactone shown in the table.

tr>
Table
The influence of reaction conditions on the conversion of pantolactone (PL) and the output of ketopantolactone (KPL).
# exampleReaction conditionsThe material of the electrodesConversion of DPS, % (number of e-VA F/mol PL)The output of CPL, % (number of e-VA F/mol PL)Paramasivan. Rev/sec
The aqueous phaseThe organic phaseT-RA, C
2pH=1, Na2SO4CVGl355-60The anode - Pt cathode - Ti98(6)85(6)1
3pH=1, Na2SO4NaBrl355-60The anode - Pt, the cathode is stainless steel. steel99(6)75(5)3
4pH=1.5, Na2SO4NaBrCCl465-70The anode - Pt, the cathode is stainless steel. steel98(6)82(6)4
5pH=0.5, Na2SO4KBrCH2Cl235-40The anode - Pt, the cathode is stainless steel. steel89(6)81(6)2
6pH=1, Na2SO4KBrl355-60The anode - Pt, the cathode is stainless steel. steel61(4)56(4)3
7pH=1, Na2SO4NaBrl355-60The graphite anode, cathode - Ti98(6)81(6)3
Comparative examples
8pH=1, Na2SO4KBrl355-60The anode - Pt, the cathode is stainless steel. steel31(4)27(4)12
9pH=1, Na2SO4KBrl355-60The anode - Pt, the cathode is stainless steel. steel54(6)44(6)12
10pH=7,Na 2SO4NaBrl355-60The anode - Pt, the cathode is stainless steel. steel55(6)49(6)2
11pH=1, Na2SO4NaBrl355-60The anode - Pt, the cathode is stainless steel. steel12(1)9(1)3
12PH=1, Na2SO4KBrl355-60The anode - Pt, the cathode is stainless steel. steel34(2)28(2)3

As can be seen from the table, in comparative examples 8 and 9 when the stirring speed is 12 Rev/sec output ketopantolactone is 27 and 44% when transmitting electricity in the number 4 and 6F / mol pantolactone respectively. With increasing pH up to 7 (example 10) output ketopantolactone is 49%. By passing an insufficient amount of electricity 1F / mol (example 11) and 2F / mol (example 12) output ketopantolactone is only 9 and 28%, respectively.

1. The method of obtaining ke is pantolactone by oxidative dehydrogenation of pantolactone under the action of bromine in the environment of chlorine-containing organic solvent under heating using an electrolyzer, equipped with an anode and a cathode, wherein the oxidative dehydrogenation of pantolactone carried out under the action of the electrochemically generated bromine from bromide anion in the electrolytic cell, is further provided with a magnetic maslinica, in a two-phase system containing organic and aqueous layers, by passing an electric current equal to 4-6 F 1 mol of pantolactone, and stirring the reaction mass with a speed of 1-4 cycles per second at a temperature of 35-70C and pH of 0.5-1.5.

2. The method according to claim 1, characterized in that as the source of the bromide anion is used salts of Hydrobromic acid.

3. The method according to claim 1, characterized in that the chlorine-based organic solvent used methylene chloride, chloroform or carbon tetrachloride.

4. The method according to claim 1, characterized in that use magnetic Mielnik with a ratio of length maslinica to the diameter of the cell from 0.5 to 0.2.

5. The method according to claim 1, characterized in that the anode is made of platinum or graphite, and the cathode is made of titanium or steel.



 

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