Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
  • C07C37/60—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by oxidation reactions introducing directly hydroxy groups on a =CH-group belonging to a six-membered aromatic ring with the aid of other oxidants than molecular oxygen or their mixtures with molecular oxygen

Definitions

• the subject of the present invention is a process for the hydroxylation of phenolic compounds and more particularly, a process for the hydroxylation of phenols and phenol ethers, with hydrogen peroxide.
• Said method consists in carrying out the hydroxylation, with hydrogen peroxide, in the presence of a strong acid.
• strong acids sulfuric acid, paratoluene sulfonic acid, perchloric acid are the most used.
• the known methods therefore mainly lead to pyrocatechol.
• the Applicant has proposed in FR-A 2,667,598, a process making it possible to increase the quantity of hydroquinone formed relative to the quantity of pyrocatechin and to obtain, in its preferred variant, more hydroquinone than pyrocatechin.
• Said method consists in carrying out the hydroxylation of phenol in the presence of an effective amount of a strong acid, said method being characterized in that the reaction is carried out in the presence of a ketone compound chosen from benzophenone and benzophenones of which the hydrogen atoms of the aromatic ring can be substituted by an electron donor group.
• the Applicant has found another process using original catalysis and making it possible to obtain good yields of diphenols and to control the selectivity of the reaction.
• the subject of the present invention is a process for the hydroxylation of a phenolic compound by hydrogen peroxide, said process being characterized in that the reaction is carried out in the presence of an effective amount of at least one rare earth or bismuth triflate.
• a first variant of the process of the invention is to carry out the reaction in the presence of an organic solvent.
• a second variant of the process of the invention consists in using a ketone compound as co-catalyst.
• a third variant of the process of the invention is to use both the co-catalyst and the organic solvent.
• the hydroxylation of a phenolic compound is carried out in the presence of a catalyst chosen from rare earth or bismuth triflates.
• rare earth or bismuth triflate is meant a rare earth or bismuth salt of trifluoromethane sulfonic acid.
• R2, R3 and R4 identical or different, represent a hydrogen atom or any substituent
• R - R ' represents a hydrogen atom or a hydrocarbon radical having from 1 to 24 carbon atoms, which can be a saturated acyclic aliphatic radical or unsaturated, linear or branched; a saturated or unsaturated, monocyclic or polycyclic cycloaliphatic radical; a saturated or unsaturated, linear or branched aliphatic radical, carrying a cyclic substituent.
• cyclic substituent is meant a saturated, unsaturated or aromatic carbocycle having, generally, from 4 to 7 carbon atoms, and preferably 6 carbon atoms.
• the process of the invention applies to any phenolic compound corresponding to the general formula (I) and, more particularly, to the phenolic compounds of formula (I) in which R 'represents: a hydrogen atom
• a linear or branched alkyl radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms. and more particularly a methyl or ethyl radical,. a cyclohexyl radical,. a benzyl radical.
• the phenolic compound of formula (I) can carry one or more substituents R-j, R2. R3 and R4. Examples of substituents are given below, but this list is in no way limiting. Any substituent can be present on the cycle as long as it does not interfere with the desired product.
• RQ one of the following groups:. a hydrogen atom,
• an alkyl radical linear or branched, having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl,
• a linear or branched alkenyl radical having from 2 to 6 carbon atoms, preferably from 2 to 4 carbon atoms, such as vinyl, allyl,
• a linear or branched aikoxy radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms such as the methoxy, ethoxy, propoxy, isopropoxy, butoxy, radicals.
• an acyl group having from 2 to 6 carbon atoms,. a radical of formula:
• R5 represents a valence bond or a divalent hydrocarbon radical, linear or branched, saturated or unsaturated, having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene;
• BQ represents a hydrogen atom or a linear or branched alkyl radical having from 1 to 6 carbon atoms;
• X symbolizes a halogen atom, preferably a chlorine, bromine or fluorine atom.
• R7 one of the following more complex radicals:
• R5 represents a valential bond or a divalent, linear or branched, saturated or unsaturated hydrocarbon radical having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene and RQ having the meaning given above and m is an integer from 0 to 4,.
• Rg represents a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, a cyclohexyl or phenyl radical.
• Ri and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them an unsaturated or aromatic carbocycle having from 4 to 7 carbon atoms and, preferably, 6 carbon atoms,
• the compounds of formula (I) are chosen in which R ′ represents a hydrogen atom and one of the radicals R-
• R-j, R2, R3 and R4 represent a hydrogen atom, such as phenol or anisole
• phenolic compounds of formula (I) which may be used in the process of the invention, there may be mentioned, without limitation, phenol, o-cresol, m-cresol, p-cresol.
• the rare earth triflate used as a catalyst is more particularly a rare earth chosen from lanthanides, yttrium scandium and their mixtures, preferably lanthanides such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium and their mixtures.
• lanthanides such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium and their mixtures.
• ceric rare earths including the elements La, Ce, Pr, Nd, and / or of yttric rare earths comprising Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
• the following rare earths are more particularly envisaged: lanthanum, ytterbium, lutetium and / or scandium.
• Rare earth triflates are known products which are described in the literature, in particular in US-A-3,615,169. They are generally obtained by reaction of rare earth oxide and trifluoromethanesulfonic acid. According to a variant of the process of the invention, the catalyst is advantageously prepared in situ by reacting trifluoromethanesulfonic acid and a source of rare earth.
• the nature of the compounds providing the various elements used for the preparation of the catalyst of the invention is not critical.
• the rare earth elements can be provided in the form of a metal or in the form of an inorganic derivative such as an oxide or a hydroxide. It is possible to use a mineral salt preferably, nitrate, sulfate, oxysulfate, halide, oxyhalide, silicate, carbonate, orthophosphate or an organic derivative, preferably oxalate, acetylacetonate; alcoholate and even more preferably methylate or ethylate; carboxylate and even more preferably acetate.
• nitrates, chlorides and / or sulfates of rare earths are used, such as cerium, lanthanum, praseodymium, neodymium, samarium, gadolinium, rytterbium and ryttrium.
• rare earths such as cerium, lanthanum, praseodymium, neodymium, samarium, gadolinium, rytterbium and ryttrium.
• compounds capable of being used for the preparation of the catalysts of the invention there may be mentioned in particular:. yttrium (III) chloride,. lanthanum chloride (III), . neodymium (III) chloride,
• the bismuth salts of trifiic acid described in patent application PCT / FR96 / 01488 can also be used in the process of the invention.
• a method of preparing bismuth triflate is given below.
• a polar aprotic organic solvent having certain characteristics of polarity and basicity; the presence of said solvent being able to improve the yield and the regioselectivity of the reaction.
• a first class of solvents suitable for the invention are polar and not very basic organic solvents, that is to say having a polarity such that its dielectric constant is greater than or equal to 20 and a basicity such that it has a "number donor "less than 25.
• Another type of solvent also suitable for the invention are organic solvents which are not very polar but basic, that is to say having a polarity such that its dielectric constant is less than about 20 and a basicity such that 'it has a "donor number" greater than or equal to 15 and less than 25.
• organic solvent A first characteristic of the organic solvent is that it is aprotic and stable in the reaction medium.
• aprotic solvent a solvent which, in Lewis theory has no protons to release.
• reaction solvents which are not stable in the reaction medium and which degrade either by oxidation or by hydrolysis.
• reaction solvents which are not suitable for the invention, mention may be made of ester type solvents derived from carboxylic acids such as in particular methyl or ethyl acetate, methyl or ethyl phthalate, methyl benzoate etc.
• the organic solvents suitable for carrying out the process of the invention must meet certain requirements in terms of their polarity and their basicity which is characterized by the donor number.
• a first class of organic solvents which are entirely suitable for carrying out the process of the invention are polar and not very basic organic solvents.
• an organic solvent which has a dielectric constant greater than or equal to 20.
• the upper bound does not is not critical. It is preferred to use an organic solvent having a high dielectric constant, preferably between 25 and 75.
• the organic solvent having the aforementioned polarity characteristics must also satisfy certain basicity conditions. Indeed, said solvent should not be too basic. To determine whether a solvent meets this requirement, its basicity is assessed by reference to the "donor number".
• a polar organic solvent is chosen having a donor number less than 25, preferably less than or equal to 20. The lower limit has no critical character.
• An organic solvent preferably having a donor number between 2 and 17 is chosen.
• the solvents belonging to this category are organic solvents which are not very polar but basic.
• An organic solvent is chosen in accordance with the invention which has a dielectric constant of less than about 20. The lower limit has no critical character. It is preferred to use an organic solvent having a low dielectric constant, preferably between 2 and 15.
• polar aprotic organic solvents which meet the aforementioned basicity characteristics, which can be used in the process of the invention, there may be mentioned more particularly:
• nitro compounds such as nitromethane, nitroethane, 1-nitropropane, 2-nitropropane or their mixtures, nitrobenzene,
• - alphatic or aromatic nitriles such as acetonitrile, propionitrile, butanenitrile, isobutanenitrile, benzonitrile, benzyl cyanide,
• ether-oxides and, more particularly, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, methyltertiobutyl ether, dipentyl ether, diisopentyl oxide, ethylene glycol dimethyl ether (or 1,2-dimethoxyethane), diethylene glycol dimethyl ether (or 1,5-dimethoxy-3-oxapentane), dioxane, tetrahydrofuran,
• - neutral phosphoric esters such as, in particular, tri-methyl phosphate, triethyl phosphate, butyl phosphate, triisobutyl phosphate, tripentyl phosphate, - ethylene carbonate.
• the hydroxylation of the phenolic compound is carried out, in the presence of a ketone compound and more particularly those corresponding to formula (II):
• R and R b identical or different, represent hydrocarbon radicals having from 1 to 30 carbon atoms or together form a divalent radical, optionally substituted by one or more halogen atoms or functional groups stable under the conditions of the reaction,
• - X represents a valence bond, a group -CO-, a group -CHOH or a group - (R) - n representing an alkylene group preferably having from 1 to 4 carbon atoms and n is an integer chosen between 1 and 16.
• R and R ⁇ more particularly represent:
• R a and R D can together form an alkylene or alkenylene radical containing from 3 to 5 carbon atoms, optionally substituted by an alkyl radical with low carbon condensation or by a cycloalkyl or cycloalkenyl radical having 4 to 6 carbon atoms; 2 to 4 carbon atoms of the alkylene or alkenylene radicals which may be part of one or two benzene rings optionally substituted by 1 to 4 hydroxyl and / or alkyl and / or aikoxy groups with low carbon condensation.
• low carbon alkyl group means a linear or branched alkyl group generally having from 1 to 4 carbon atoms.
• hydrocarbon radicals can be substituted by 1 or more, preferably 1 to 4, low carbon condensation alkyl groups or functional groups such as hydroxyl groups, low carbon condensation aikoxy, hydroxycarbonyls, alkyloxycarbonyls comprising from 1 to 4 carbon atoms in the alkyl group, a nitrile group, -SOgH, nitro or by one or more halogen atoms, and in particular of chlorine and bromine.
• R a and R D more particularly represent:
• R and Ru can together form an alkylene or alkenylene radical containing 3 to 5 carbon atoms, optionally substituted by 1 to 4 alkyl radicals with low carbon condensation.
• ketones which can be used in the process of the invention, there may be mentioned, more particularly:
• ketone compounds of the dialkylketone type corresponding to formula (II) in which R a and Rt represent a linear or branched alkyl radical having from 1 to 8 carbon atoms and to alkylphenones that is to say R a represents a linear or branched alkyl radical having from 1 to 6 carbon atoms and Rb represents a phenyl radical.
• R a and Rt represent a linear or branched alkyl radical having from 1 to 8 carbon atoms and to alkylphenones that is to say R a represents a linear or branched alkyl radical having from 1 to 6 carbon atoms and Rb represents a phenyl radical.
• dialkylketones and alkylphenones mention may be made of pentanones, acetophenone and n-valerophenone.
• R and R d which are identical or different, represent a hydrogen atom or a substituent, preferably an electron donor group,
• n identical or different is a number equal to 0, 1, 2 or 3, - optionally the two carbon atoms located in position a with respect to the two carbon atoms carrying the group -CO can be linked together by a valential bond or by a group -CHg- thus forming a ketone cycle which can be saturated but also unsaturated.
• the substituent is chosen so that it does not react under the acidity conditions of the invention. It is preferably an electron donor group.
• electron donor group is understood to mean a group as defined by HC BROWN in the work of Jerry MARCH - Advanced Organic Chemistry, chapter 9, pages 243 and 244 (1985).
• substituents which are very suitable for the invention are the following: - linear or branched alkyl radicals having from 1 to 4 carbon atoms,
• R-J O represents a linear or branched alkyl radical having from 1 to 4 carbon atoms or the phenyl radical, - the hydroxyl group
• ketone compounds corresponding to the formula (IIa) are used in which R Q and R ⁇ , which are identical or different, represent a hydrogen atom; a methyl, ethyl, tert-butyl, phenyl radical; a methoxy or ethoxy radical; a hydroxyl group, preferably in the 3.3 ′ or 4.4 ′ position.
• R Q and R ⁇ which are identical or different, represent a hydrogen atom; a methyl, ethyl, tert-butyl, phenyl radical; a methoxy or ethoxy radical; a hydroxyl group, preferably in the 3.3 ′ or 4.4 ′ position.
• hydrogen peroxide a catalyst optionally an organic solvent and / or a ketone compound is used during the hydroxylation process of the phenolic compound of formula (I).
• the hydrogen peroxide used according to the invention can be in the form of an aqueous solution or an organic solution.
• aqueous solutions being commercially more readily available are used.
• concentration of the aqueous hydrogen peroxide solution is chosen so as to introduce as little water as possible into the reaction medium.
• an aqueous solution of peroxide is used hydrogen at least 20% by weight of H2O2 and preferably around 70%.
• the amount of hydrogen peroxide can range up to 1 mole of H2O2 per 1 mole of phenolic compound of formula (I). It is however preferable, in order to obtain an industrially acceptable yield, to use a molar ratio of hydrogen peroxide / phenolic compound of formula (I) of 0.01 to 0.3 and, preferably, of 0.05 to 0.10.
• the initial water content of the medium is limited to 10% by weight and, preferably, to 5% by weight.
• the weight contents indicated are expressed relative to the mixture of phenolic compound of formula (1) / hydrogen peroxide / water.
• This initial water corresponds to the water introduced with the reagents and in particular with the hydrogen peroxide.
• the amount of catalyst expressed by the ratio between the number of moles of triflate and the number of moles of hydrogen peroxide advantageously varies between 10 -4 and 10 ' 1 , preferably between 10 * 3 and 5.10 -3 .
• the amount of organic solvent to be used is determined according to the nature of the organic solvent chosen.
• the molar ratio between the number of moles of organic solvent and the number of moles of phenolic compound of formula (I) varies between 0.1 and 2.0, preferably between 0.25 and 1.0.
• the quantity used is determined so that the molar ratio between the number of moles of organic solvent and the number of moles of phenolic compound of formula (I) varies between 0.01 and 0.25, preferably between 0.025 and
• the ketone compound of formula (II) which has been previously defined intervenes in an amount defined below.
• the amount of the ketone compound of formula (II) expressed in moles per mole of hydrogen peroxide varies between 1.10 "3 mole and 10. It is not necessary to exceed 1.0 mole of ketone compound per mole of peroxide
• the amount of ketone compound is most often between 0.05 and 1.0 mole per mole of hydrogen peroxide
• the hydroxylation of the compound is carried out.
• a preferred variant of the process of the invention consists in choosing the temperature between 50 ° C and 80 ° C.
• the reaction is advantageously carried out at atmospheric pressure.
• the method according to the invention is simple to implement continuously or discontinuously.
• the following different reagents are introduced in any order, phenolic compound of formula (I), catalyst, ketone compound of formula (II), organic solvent.
• the reaction medium is brought to the desired temperature and then the hydrogen peroxide solution is added gradually.
• the unconverted phenolic compound and the ketone compound of formula (II) are separated from the hydroxylation products by the usual means, in particular by distillation and are returned to the reaction zone.
• Test a is a comparative example.
• the following abbreviations mean:
• the phenol is charged into a 100 ml glass flask fitted with a central stirrer, a condenser, a dropping funnel and a thermometer.
• the catalyst rare earth or bismuth triflate, optionally the ketone compound of formula (II), the solvent.
• reaction mixture is brought to the chosen reaction temperature, ie
• reaction mixture is then cooled and the reaction products are assayed: the residual hydrogen peroxide is assayed by iodometry and the diphenols formed are assayed by high performance liquid chromatography.
• ketone compound namely acetophenone.
• the tests are carried out according to the operating protocol previously defined.
• bismuth triflate is used as catalyst.
• the latter can be prepared as follows:
• the reaction mixture is allowed to return to room temperature.
• the solid obtained is filtered under argon and washed with dry dichloromethane in order to remove the traces of triflic acid.
• the powder is introduced into a two-necked bottle and dried under reduced pressure (18 mm of mercury), under argon, for 1 hour.

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• 1996
  • 1996-02-09 FR FR9601596A patent/FR2744720B1/fr not_active Expired - Fee Related
• 1997
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  • 1997-02-05 WO PCT/FR1997/000223 patent/WO1997029066A1/fr not_active Application Discontinuation
  • 1997-02-05 US US09/125,163 patent/US6040484A/en not_active Expired - Fee Related
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