NO904328L - PROCEDURE FOR THE PREPARATION OF BENZALDE HYDERS. - Google Patents

Abstract

Process for the preparation of alkoxybenzaldehydes from halobenzaldehydes. The invention relates more particularly to the preparation of 3-alkoxy-4-hydroxybenzaldehydes from 3-halo-4-hydroxy- benzaldehydes and of 5-alkoxy-2-hydroxybenzaldehydes from 5-halo- 2-hydroxybenzaldehydes. More precisely, the invention consists of a process for the preparation of alkoxybenzaldehydes by reaction of halobenzaldehydes with an alkali metal or alkaline-earth metal alcoholate in the presence of copper or of a copper compound, characterised in that it is carried out in the presence of an effective quantity of an organic carbonate, of a mixed organometallic carbonate, of carbon dioxide or of a compound capable of forming carbon dioxide in the reaction mixture.

Description

The present invention relates to a process for the production of alkoxybenzaldehydes from halogenobenzaldehydes and relates in particular to the production of 3-alkoxy-4-hydroxybenzaldehydes from 3-halogeno-4-hydroxybenzaldehydes and 5-hydroxy-2-hydroxybenzaldehydes from 5-halogeno-2-hydroxybenzaldehydes.

An article in Canadian Journal Chemistry 31, page 476 (1953) describes the methoxylation of 5-halogeno-4-hydroxy-3-methoxy-benzaldehydes (or 5-halogenovanilines) using sodium methylate in methanol and in the presence of a copper II compound .

The yield obtained with the bromine derivative is approximately 60%.

U.S. patent document 4218567 describes in particular the production of 3,5-dimethoxy-4-hydroxybenzaldehyde.

GB-A-2089672 describes the preparation of 3,5-dimethoxy-4-hydroxybenzaldehyde from 5-bromo-4-hydroxy-3-methoxybenzaldehyde and sodium methylate in the presence of a catalyst consisting of a formic acid ester and copper I salt. In this method, the aldehyde function is protected in advance by conversion to an acetal. The reaction takes place very slowly.

The present invention relates to carrying out the alkoxylation of halogenobenzaldehydes in a solvent, preferably an alcohol, and without it being necessary to protect the aldehyde function in the form of an acetal.

In the following description of the invention, "halogenobenzaldehyde" is understood to mean any aromatic compound that carries at least one aldehyde function and at least one halogen atom.

In more detail, the invention constitutes a method for the production of alkoxybenzaldehydes by reaction between:

- a halobenzaldehyde of general formula (I):

in which:

- X stands for a halogen atom, preferably an iodine atom, bromine atom or chlorine atom - Rq stands for an aromatic cyclic radical with at least 5 atoms in the ring, possibly substituted, and represents at least one of the following radicals: . a monocyclic or polycyclic aromatic carbocyclic radical. a monocyclic or polycyclic aromatic heterocyclic radical containing at least one of the heteroatoms 0, N and S, - and an alkali metal alcoholate of general formula (II):

in which:

- M stands for an alkali metal or alkaline earth metal,

- m stands for the valence of the alkali metal or alkaline earth metal, - R stands for a hydrocarbon radical with 1 to 12 carbon atoms which can be a saturated or unsaturated, linear or branched, acyclic aliphatic radical or a

arylaliphatic radical,

in the presence of copper and/or a copper compound, and the peculiarity of the method according to the invention is that one works in the presence of an effective amount of an organic carbonate, a mixed organo-metallic carbonate, carbon dioxide or a compound which can form carbon dioxide in the reaction mixture.

The invention relates in particular to compounds for use of the starting compound of formula (I) in which the radical Rq stands for: 1° - a monocyclic or polycyclic aromatic carbocyclic radical.

"Polycyclic carbocyclic radical" means:

. a radical which consists of at least 2 aromatic carbocycles and which together form ortho systems or ortho- and peri-condensed systems, . a radical consisting of at least 2 carbocycles of which at least one is aromatic and which together form ortho-systems or ortho- and perio-condensed systems.

2° - a monocyclic or polycyclic aromatic heterocyclic radical.

By "polycyclic heterocyclic radical" is defined:

. a radical which consists of at least 2 heterocycles containing at least one heteroatom in each cycle where at least one of the two cycles is aromatic and which together form ortho-systems or ortho- and peri-condensed systems, . a radical which consists of at least one hydrocarbon cycle and at least one heterocycle where at least one of the cycles is aromatic and which together form ortho systems or ortho- and peri-condensed systems.

3° - a divalent radical which is formed by a chain of groups, as defined in paragraphs 1 and/or 2 which are interconnected:

. with a valence bond,

. with an alkylene radical or alkylidene radical with 1 to 4 carbon atoms, preferably a methylene radical or isopropylidene radical,

. with one of the following groups:

wherein in these formulas, R' stands for an alkyl radical of 1 to 4 carbon atoms, a cyclohexyl radical or phenyl.

Examples of radicals listed under 1° to 3° above can be mentioned:

1° - the radicals phenylene, tolylene, xylylene, naphthylene,

2° - the radicals pyrrolidinediyl, imidazolidindiyl, piperidinediyl, furandiyl, pyrroldiyl, thiophendiyl, isoxazoldiyl, furazandiyl, isothiazoldiyl, imidazoldiyl, pyrazoldiyl, pyridinediyl, pyridazinediyl, pyrimidindiyl, the radicals naphthyridin-1,8-diyl, quinolidiyl, indoldiyl, benzofurandiyl.

3° - the radicals biphenylene, 1,1'-methylenebiphenylene, 1,1'-isopropylidenebiphenylene, 1,1'-oxybiphenylene, 1,1'-imino-biphenylene.

As mentioned above, the radical Rg, which is an aromatic compound bearing at least one aldehyde function and at least one halogen atom, may also carry other substituents which may be an additional halogen atom or of any other nature to the extent that this does not compete with the reaction the one.

As examples of substituents given for illustrative purposes, the following can be mentioned:

- one or more alkyl radicals with 1 to 4 carbon atoms,

- one or more alkoxy radicals with 1 to 4 carbon atoms,

- one or more hydroxyl radicals.

As examples of starting halogenobenzaldehydes that correspond to general formula (I) the following can be mentioned in particular:

2- bromobenzaldehyde

3-bromobenzaldehyde

4-bromobenzaldehyde

5-bromo-2-methoxybenzaldehyde

4- bromothiophenecarboxaldehyde-2

5-bromothiophenecarboxaldehyde-3

Among the compounds that correspond to the general formula (I), the invention is particularly suitable for the production of starting halogenohydroxybenzaldehydes that correspond to the general formula:

in which:

- X stands for an iodine atom, bromine atom or chlorine atom,

- R]_ stands for a hydrogen atom, iodine atom, bromine atom, chlorine atom, alkyl with 1 to 4 carbon atoms, alkoxy with 1 to 4 carbon atoms, or a hydroxyl radical,

in that in the above-mentioned formula (Ia) the hydroxyl radical can be in the ortho-, meta- or para-position in relation to the aldehyde function.

In particular, mention may be made of compounds with the general formula (Ia) in which:

.Group I :

- the radical OH is in the para position in relation to the CHO function, - the halogen atom X is in the ortho position in relation to the radical OH, - the radical R^ is in the ortho position in relation to the radical

OH.

.Group II :

- the radical OH is in the ortho position in relation to the CHO function, - the halogen atom X is in the para position in relation to the radical OH, - the radical R^ is in the ortho position in relation to the radical

OH.

.Group III :

- the radical OH is in the ortho position in relation to the CHO function, - the halogen atom X is in the ortho position in relation to the radical OH, - the radical R]_ is in the para position in relation to the radical

OH.

. Group IV:

- the radical OH is in the meta position in relation to the CHO function, - the halogen atom X is in the ortho position in relation to the radical OH, - the radical R]_ is in the para position in relation to the radical

OH.

.Group V :

- the radical OH is in the meta position in relation to the CHO function, - the halogen atom X is in the para position in relation to the radical OH, - the radical R^_ is in the ortho position in relation to the radical

OH.

The starting compounds of formula (Ia) which are preferably used correspond in more detail to the following formulas:

in which:

- X and Ri have the previously stated meanings.

As examples of halogenobenzaldehydes corresponding to formula (Ia) which can serve as starting substrates in the present process, the following can be more particularly mentioned: 3-bromo-4-hydroxybenzaldehyde

3-iodo-4-hydroxybenzaldehyde

3,5-dibromo-4-hydroxybenzaldehyde

3,5-diiodo-4-hydroxybenzaldehyde

3-bromo-5-methoxy-4-hydroxybenzaldehyde 3-iodo-5-methoxy-4-hydroxybenzaldehyde

3-Bromo-5-ethoxy-4-hydroxybenzaldehyde

3-iodo-5-ethoxy-4-hydroxybenzaldehyde

3-bromo-4,5-dihydroxybenzaldehyde

3-iodo-4,5-dihydroxybenzaldehyde

3-bromo-2,5-dihydroxybenzaldehyde

3-iodo-2,5-dihydroxybenzaldehyde

2-bromo-4-hydroxybenzaldehyde

2-iodo-4-hydroxybenzaldehyde

4-bromo-3-hydroxybenzaldehyde

4-iodo-3-hydroxybenzaldehyde

3-bromo-2-hydroxybenzaldehyde

3-iodo-2-hydroxybenzaldehyde

5-bromo-2-hydroxybenzaldehyde

5-iodo-2-hydroxybenzaldehyde

With regard to the definition of the alkali metal or alkaline earth metal alcoholate, those corresponding to formula (II) in which R stands for linear or branched alkyl, alkenyl, alkadinyl, alkynyl with preferably at least 6 carbon atoms or a benzyl radical are used above all.

Among the above-mentioned alcoholates, alcoholates of alkali metals are preferably used in the method according to the invention, and sodium or potassium alcoholates of primary or secondary alkanols with 1 to 4 carbon atoms are particularly suitable.

The most commonly used alcoholates are sodium methylate and sodium ethylate.

In accordance with the process according to the invention, a halobenzaldehyde of formula (I) can be reacted with an alkali metal or alkaline earth metal alcoholate of formula (II) in the presence of a copper catalyst and an effective amount of an organic carbonate, a mixed organo- metallic carbonate, carbon dioxide or a compound capable of forming carbon dioxide in the reaction mixture.

The organic carbonates and the mixed organo-metallic carbonates used in the invention are carbonates with general formula (III):

in which:

- R2 stands for

- linear or branched alkyl with 1 to 6 carbon atoms,

- aryl,

- aryl substituted with 1 or 2 alkyl radicals with 1 to 12 carbon atoms,

- cycloalkyl with 5 to 6 carbon atoms,

- cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 12 carbon atoms, - a radical R4-O-CO- in which R4 stands for linear or branched alkyl with 1 to 6 carbon atoms, aryl,

or cycloalkyl with 5 or 6 carbon atoms,

- R3 stands for

- linear or branched alkyl with 1 to 6 carbon atoms,

- aryl,

- aryl substituted with 1 or 2 alkyl radicals with 1 to 12 carbon atoms,

- cycloalkyl with 5 or 6 carbon atoms,

- cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 12 carbon atoms, - an alkali metal or alkaline earth metal, preferably sodium or potassium,

- n = 1 or n = 2 when R3 stands for an alkaline earth metal,

- R2 and R3 combine to form an alkylene radical with 2 to 6 carbon atoms.

Preferred are the organic carbonates and the mixed organo-metallic carbonates carbonates with general formula (IV):

in which:

- R2 stands for

- linear or branched alkyl with 1 to 6 carbon atoms,

- phenyl,

- phenyl substituted with 1 or 2 alkyl radicals with 1 to 4 carbon atoms,

- cycloalkyl with 5 to 6 carbon atoms,

- cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 4 carbon atoms, - a radical R4-O-CO- in which R4 stands for linear or branched alkyl with 1 to 6 carbon atoms, phenyl

or cycloalkyl with 5 or 6 carbon atoms,

- R3 stands for

- linear or branched alkyl with 1 to 6 carbon atoms,

- phenyl,

- phenyl substituted with 1 or 2 alkyl radicals with 1 to 4 carbon atoms,

- cycloalkyl with 5 or 6 carbon atoms,

- cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 4 carbon atoms,

- a sodium atom or potassium atom,

- R2 and R3 together form an alkylene radical with 2 to 6 carbon atoms.

The carbon dioxide can be used in solution in the liquid reaction mixture by circulation therein or by means of an above-atmospheric pressure.

When using a pressure of carbon dioxide, this is generally 0.1 to 5 MPa.

As examples of organic organo-metallic carbonates can be mentioned: di-tert-butyl carbonate, diethyl carbonate, dimethyl carbonate, ethylene carbonate, propylene carbonate, phenyl tert-butyl carbonate, tert-butyl sodium carbonate and di-tert-butyl dicarbonate.

As examples of compounds that can form carbon dioxide in the reaction mixture, the following can be mentioned:

- a(or P)ketoesters and ct(or |3)ketoacids,

- amine carbonates, urea derivatives and carbodiimides,

- dicarboxylic acids such as malonic acid, a-cyano- or a-nitro-carboxylic acids,

- p^-unsaturated carboxylic acids.

The copper compounds which serve as catalysts are known. These are generally all organic or inorganic compounds of copper I or copper II.

Copper metal can be used, but its effect is slower as it must first be partially converted to copper I or copper

II.

Examples of copper compounds include: cupric chloride, cupric chloride, cupric carbonate, basic copper II carbonate, cupric nitrate, cupric nitrate, cupric sulfate, cupric acetate, cupric trifluoromethyl sulfonate, cupric hydroxide, copper II picolinate, copper I methylate, copper II methylate, chelate of copper II and 8-quinoline and copper compounds with the formula CICUOCH3or Cu2(OCH3)2(acac)2•

In accordance with the method according to the invention, the alkoxylation of the halogenobenzaldehyde with formula (I) is carried out in an organic environment which is most often made up of the alkanol corresponding to the alcoholate of the alkali metal or alkaline earth metal used.

The preferred solvent is methanol or ethanol.

The concentration of the compound of (I) expressed as % by weight of the compound (I) in relation to the total weight of the compound (I) + solvent is generally 3 to 40% by weight, preferably 10 to 30% by weight.

The amount of alcoholate of alkali metal or alkaline earth metal used is equal to or greater than the necessary stoichiometric amount, on the one hand, to convert the compound of formula (I) into the phenolate of alkali metal or alkaline earth metal (ie for salt formation of the OH group or the OH groups), and on the other hand to convert the halogen atom or

-atoms of alkoxy groups.

In general, the alcoholate of alkali metal or alkaline earth metal used is 1 to 4 times the stoichiometric amount as defined, and preferably 1.5 to 3 times.

Practically, the alcoholate of alkali metal or alkaline earth metal is formed in situ by reacting an excess of alkanol with the selected alkali metal or alkaline earth metal.

The amount of copper catalyst used in the method according to the invention can vary within wide limits.

Usually the molar ratio of copper catalyst/compound of formula (I) is 1 to 50%, and preferably 2 to 20%.

The amount of organic carbonate or organo-metallic carbonate of formula (III) or (IV) that is usually used is such that one has a molar ratio between carbonate of formula (III) or (IV)/copper catalyst of 1 to 50, and preferably 1 to 10.

The temperature of the alkoxylation reaction is generally between 90 and 220°C, and preferably from 100 to 180°C.

The pressure is not a critical parameter in itself, apart from the dissolution of the carbon dioxide when this is used, but in order to achieve the above-mentioned temperatures and not lose solvent, the process is usually carried out under autogenous pressure.

In general, this autogenous pressure from the reaction mixture is at most 5 MPa (50 bar).

The duration of the alkylation reaction can vary greatly between 2 and 10 hours, and is preferred between 3 and 5 hours.

The method according to the invention is very well suited for the production of 3,4,5-trimethoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 2-hydroxy-5-methoxybenzaldehyde.

One of the particularly interesting advantages of the method according to the invention is that it allows the alkoxylation reaction to be carried out without it being necessary to protect the aldehyde function.

A further advantage of the method according to the invention is that it uses a common solvent which is inexpensive and which can be easily recycled.

The following examples illustrate the invention.

EXAMPLE 1

In a Teflon reactor of 40 cm^ equipped with a system for heating and stirring, introduce: - 2.22 g (9.62 mmol) 3-bromo-4-hydroxy-5-methoxybenz-aldehyde (BHMB) - 25 g of a methanolic solution containing 2 g (37 mmol) sodium methylate

- 0.099 g (1 mmol) cupric chloride.

Dry carbon dioxide is bubbled through this suspension for 30 seconds, after which the mixture is heated for 3 hours at 125°C under stirring and autogenous pressure. The mixture is cooled to normal temperature, diluted with distilled water, the pH of the reaction mixture is adjusted to 4 using sulfuric acid and insoluble parts are filtered off.

Using liquid phase chromatography, the following is determined:

Conversion rate of BHMB (TT%) : 100%

Yield (RT %) of syringaldehyde

(4-hydroxy-3,5-dimethoxybenzaldehyde) : 97.5%

EXAMPLE 2

Example 1 is repeated with the same quantities, the same working conditions, but the work is done under a nitrogen atmosphere and the carbon dioxide is replaced with 4 mmol of di-tert-butyl dicarbonate.

After treatment, the following results are achieved:

TT % of BHMB : 100%

RT % of syringaldehyde : 96%

COMPARISON EXPERIMENT A

Example 2 is repeated with the same quantities and the same working conditions, but the di-tert-butyl dicarbonate is replaced with 0.70 g (11 mmol) of methyl formate.

The following results are achieved:

TT % of BHMB : 68%

RT % of syringaldehyde : 93%

EXAMPLE 3

Example 1 is repeated with the same amounts and the same working conditions, but the carbon dioxide is replaced with 0.440 g (5 mmol) of ethylene carbonate, and the cupric chloride is replaced with 0.110 g of basic copper (II) carbonate.

After treatment, the following results are achieved:

TT % of BHMB : 98%

RT % of syringaldehyde : 93%

EXAMPLE 4

Example 3 is repeated with the same quantities, the same reaction components and the same working conditions, but the ethylene carbonate is replaced with 0.42 g (4 mmol) of propylene carbonate and the reaction is carried out at 150°C.

After treatment, the following results are achieved:

TT % of BHMB : 100%

RT % of syringaldehyde : 89%

EXAMPLE 5

Example 3 is repeated with the same quantities and the same working conditions, but the ethylene carbonate is replaced by 0.5 cm^ (4 mmol) of diethyl carbonate.

After treatment, the following results are achieved:

TT % of BHMB : 97%

RT % of syringaldehyde : 96%

EXAMPLE 6

In a Teflon reactor of 40 cm^ equipped with a system for heating and stirring, introduce:

- 2.10 g 95% 4-hydroxy-3-bromobenzaldehyde (HBB)

- 2.16 g sodium methylate

- 0.110 g basic copper carbonate

- 25 ml of methanol.

Dry carbon dioxide is bubbled through this solution for 30 seconds, after which the mixture is heated for 5 hours at 125°C (under autogenous pressure) with stirring. The mixture is cooled to normal temperature, diluted with distilled water, the pH of the reaction mixture is adjusted to 4 using sulfuric acid and the insoluble substance is filtered off.

The following is determined by chromatography in the liquid phase:

TT % of HBB : 100%

RT % of vanillin : 99%

EXAMPLE 7

In a Teflon reactor of 400 cm<3>equipped with a system for heating and stirring, introduce: - 21.3 g of 3-bromo-4-hydroxy-5-methoxybenzaldehyde (BHMB)

(purity 98%)

- 21.6 g sodium methylate

- 1.10 g basic copper carbonate

- 4.40 g of ethylene carbonate

- 250cm<3>methanol.

The mixture is heated for 3 hours at 125°C (under autogenous pressure) with stirring. The mixture is cooled to 40°C, diluted with distilled water, and the pH of the reaction mixture is adjusted to 4 using concentrated sulfuric acid, the reaction mixture is filtered, after which the solvent is evaporated under vacuum. The reaction mixture is extracted twice with hot toluene, filtered and the toluene evaporated under vacuum.

17.25 g of syringaldehyde (purity 95%) is obtained.

Yield of syringaldehyde: 91%

Analyzes : C, 59.13%

H, 5.60%

Theoretical : C, 59.33%

H, 5.53%

EXAMPLE 8

Example 7 is repeated with the same quantities and the same working conditions, but the ethylene carbonate is replaced with 5 cm<3> (59 mmol) of dimethyl carbonate. The mixture is heated for 3 hours at 150°C.

After treatment, the following results are achieved:

TT % of BHMB : 98%

RT % of syringaldehyde : 94%

EXAMPLE 9

Example 7 is repeated with the same quantities and the same working conditions, but the dimethyl carbonate is replaced with 5 cm<3> (40 mmol) of diethyl carbonate. The mixture is heated for 3 hours and 30 minutes at 150°C.

After treatment, the following results are achieved:

TT % of BHMB : 99%

RT % of syringaldehyde : 92%

EXAMPLE 10

•In a Teflon reactor of 40 cm<3>equipped with a system for heating and stirring -introduce:

- 2.79 g 3,5-dibromo-4-hydroxybenzaldehyde (DBHB)

- 0.406 g of copper II trifluoromethylsulfonate

- 2.70 g of sodium methylate

- 3 5 cm<3>methanol..

Dry carbon dioxide is bubbled through this suspension for 30 seconds, after which the mixture is heated for 4 hours at 150°C (under autogenous pressure) with stirring. Then continue as in example 1.

The following results are achieved:

TT % of DBHB : 100%

RT % of syringaldehyde : 87%

RT % of bromovanillin : 9%

EXAMPLE 11

In a Teflon reactor of 40 cm<3>equipped with a system for heating and stirring, introduce:

- 4.1 g (20 mmol) 5-bromo-2-hydroxybenzaldehyde (BHB)

- 0.221 g (1 mmol) cupric carbonate Cu(OH)2CuC03

- 15cm<3>methanol.

While stirring, 14.4 g of a methanol solution containing 4.32 g (80 mmol) of sodium methylate are added.

Dry carbon dioxide is bubbled through this solution for 30 seconds, after which it is heated for 4 hours at 125°C (under autogenous pressure) with stirring. The mixture is cooled to normal temperature, diluted with distilled water, the pH of the reaction mixture is adjusted to 4 using sulfuric acid and insoluble matter is filtered off.

By chromatography in the liquid phase, the following is determined: Degree of conversion of BHB (TT %) : 58 % Yield (RT %) of 2-hydroxy-5-methoxybenzaldehyde : 79 %

Claims (20)

1. Process for the production of alkoxybenzaldehydes by reaction between:- a halogenobenzaldehyde with general formula (I): in which: - X stands for a halogen atom, preferably an iodine atom, bromine atom or chlorine atom - Rg stands for an aromatic cyclic radical with at least 5 atoms in the ring, optionally substituted, and represents at least one of the following radicals: . a monocyclic or polycyclic aromatic carbocyclic radical . a monocyclic or polycyclic aromatic heterocyclic radical containing at least one of the heteroatoms 0, N and S, - and an alkali metal alcoholate of general formula (II): in which: - M stands for an alkali metal or alkaline earth metal, - m stands for the valence of the alkali metal or alkaline earth metal, - R stands for a hydrocarbon radical with 1 to 12 carbon atoms which can be a saturated or unsaturated, linear or branched, acyclic aliphatic radical or an arylaliphatic radical, in the presence of copper and/or a copper compound, characterized by working in the presence of an effective amount of an organic carbonate, a mixed organo-metallic carbonate, carbon dioxide or a compound which can form carbon dioxide in the reaction mixture. 2. Method as stated in claim 1, characterized in that the halogenobenzaldehyde corresponds to the general formula (I) in which the radical Rq symbolizes: 1° - a monocyclic or polycyclic aromatic carbocyclic radical. 2° - a monocyclic or polycyclic aromatic heterocyclic radical. 3° - a divalent radical which is formed by a chain of groups, as defined in paragraphs 1 and/or 2 which are interconnected: . with a valence bond, . with an alkylene radical or alkylidene radical with 1 to 4 carbon atoms, preferably a methylene radical or isopropylidene radical, . with one of the following groups: wherein in these formulas, R' stands for an alkyl radical of 1 to 4 carbon atoms, a cyclohexyl radical or phenyl. 3. Method as stated in claim 1 or 2, characterized in that the halogenobenzaldehyde corresponds to the general formula (I): in which: - X stands for an iodine atom, bromine atom or chlorine atom, - R] _ stands for a hydrogen atom, iodine atom, bromine atom, chlorine atom, alkyl with 1 to 4 carbon atoms, alkoxy with 1 to 4 carbon atoms, or a hydroxyl radical, in that in the above-mentioned formula (Ia) the hydroxyl radical can be in the ortho-, meta- or para-position in relation to the aldehyde function. 4. Procedure as specified in one or more of claims 1 to 3, characterized in that the halogenobenzaldehyde corresponds to the general formula (Ia) in which: . Group I: - the radical OH is in the para position in relation to the CHO function, - the halogen atom X is in the ortho position in relation to the hydroxyl radical OH, - the radical R^ is in the ortho position in relation to the radical OH. . Group II: - the radical OH is in the ortho position in relation to the CHO function, - the halogen atom X is in the para position in relation to the radical OH, - the radical R^ is in the ortho position in relation to the radical OH. . Group III: - the radical OH is in the ortho position in relation to the CHO function, - the halogen atom X is in the ortho position in relation to the radical OH, - the radical R^ is in the para position in relation to the radical OH. . Group IV : - the radical OH is in the meta position in relation to the CHO function, - the halogen atom X is in the ortho position in relation to the radical OH, - the radical R] _ is in the para position in relation to the radical OH. . Group V: - the radical OH is in the meta position in relation to the CHO function, - the halogen atom X is in the para position in relation to the radical OH, - the radical R^ is in the ortho position in relation to the radical OH. 5. Procedure as stated in one or more of claims 1 to 4, characterized in that the halogenobenzaldehyde corresponds to one of the following formulas: in which: - X and Ri have the previously stated meanings. 6. Procedure as specified in one or more of claims 1 to 5, characterized in that the halogenobenzaldehyde is chosen from: 3-bromo-4-hydroxybenzaldehyde 3-iodo-4-hydroxybenzaldehyde 3,5-dibromo-4-hydroxybenzaldehyde 3,5-diiodo-4-hydroxybenzaldehyde 3-bromo-5-methoxy-4-hydroxybenzaldehyde 3-iodo-5- methoxy-4-hydroxybenzaldehyde - 3-bromo-5-ethoxy-4-hydroxybenzaldehyde 3-iodo-5-ethoxy-4-hydroxybenzaldehyde 3-bromo-4,5-dihydroxybenzaldehyde 3-iodo-4,5-dihydroxybenzaldehyde 3-bromo-2,5- dihydroxybenzaldehyde 3- iodo-2,5-dihydroxybenzaldehyde 2-bromo-4-hydroxybenzaldehyde 2- iodo-4-hydroxybenzaldehyde 4- bromo-3-hydroxybenzaldehyde 4- iodo-3-hydroxybenzaldehyde 3- bromo-2-hydroxybenzaldehyde 3-iodo-2 -hydroxybenzaldehyde 5-bromo-2-hydroxybenzaldehyde 5-iodo-2-hydroxybenzaldehyde 7. Process in one or more of claims 1 to 6, characterized in that the alcoholate of alkali metal or alkaline earth metal corresponds to the general formula (II) in which R stands for linear or branched alkyl, alkenyl, alkadinyl, alkynyl with preferably at least 6 carbon atoms or a benzyl radical. 8. Procedure as specified in one or more of claims 1 to 7, characterized in that the alcoholate of alkali metals is an alcoholate of sodium or potassium of primary or secondary alkanols with 1 to 4 carbon atoms. 9. Procedure as specified in one or more of claims 1 to 8, characterized in that the alkali metal alcoholate is sodium methylate or sodium ethylate. 10. Procedure as specified in one or more of claims 1 to 9, characterized by working in the presence of a carbonate with general formula (III): [R2 -0-CO-0-]n- <R>3 (III) in which: - R2 stands for - linear or branched alkyl with 1 to 6 carbon atoms, - aryl, - aryl substituted with 1 or 2 alkyl radicals with 1 to 12 carbon atoms, - cycloalkyl with 5 to 6 carbon atoms, - cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 12 carbon atoms, - a radical R4 -0-C0- in which R4 stands for linear or branched alkyl with 1 to 6 carbon atoms, aryl, or cycloalkyl with 5 or 6 carbon atoms, - R3 stands for - linear or branched alkyl with 1 to 6 carbon atoms, - aryl, - aryl substituted with 1 or 2 alkyl radicals with 1 to 12 carbon atoms, - cycloalkyl with 5 or 6 carbon atoms, - cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 12 carbon atoms, - an alkali metal or alkaline earth metal, preferably sodium or potassium, - n = 1 or n = 2 when R3 stands for an alkaline earth metal, - R2 and R3 together form an alkylene radical with 2 to 6 carbon atoms. 11. Procedure as specified in one or more of claims 1 to 10, characterized by working in the presence of a carbonate with general formula (IV): in which: - R2 stands for - linear or branched alkyl with 1 to 6 carbon atoms, - phenyl, - phenyl substituted with 1 or 2 alkyl radicals with 1 to 4 carbon atoms, - cycloalkyl with 5 to 6 carbon atoms, - cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 4 carbon atoms, - a radical R4 -O-CO- in which R4 stands for linear or branched alkyl with 1 to 6 carbon atoms, phenyl or cycloalkyl with 5 or 6 carbon atoms, - R3 stands for - linear or branched alkyl with 1 to 6 carbon atoms, - phenyl, - phenyl substituted with 1 or 2 alkyl radicals with 1 to 4 carbon atoms, - cycloalkyl with 5 or 6 carbon atoms, - cycloalkyl with 5 or 6 carbon atoms substituted by 1 or 2 alkyl radicals with 1 to 4 carbon atoms, - a sodium atom or potassium atom, - R2 and R3 together form an alkylene radical with 2 to 6 carbon atoms. 12. Procedure as specified in one or more of claims 1 to 11, characterized by using carbon dioxide, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate or di-tert-butyl dicarbonate. 13. Method as specified in one or more of claims 1 to 12, characterized in that the copper catalyst is copper metal or a copper compound which is an organic or inorganic compound of copper I or copper II, chosen from among: cupric chloride, cupric chloride, cupric carbonate, basic copper II carbonate, cupric nitrate, cupric nitrate, cupric sulfate, cupric acetate, cupric trifluoromethyl sulfonate, cupric hydroxide, copper II-picolinate, copper I-methylate, copper II-methylate, chelate of copper II and 8-quinoline and copper compounds with the formula ClCuOCH3 or Cu2 (OCH3 )2 (acac)2 • 14. Procedure as specified in one or more of claims 1 to 13, characterized in that the amount of alcoholate of alkali metal or alkaline earth metal used is equal to or greater than the necessary stoichiometric amount to convert the compound of formula (I) into the corresponding phenolate of alkali metal or alkaline earth metal, and to convert the halogen atom or atoms into alkoxy groups. 15. Method as stated in one or more of claims 1 to 14, characterized in that the molar ratio between copper catalyst/compound of formula (I) is 1 to 50%, and preferably 2 to 20%. 16. Procedure as specified in one or more of claims 1 to 15, characterized in that the reaction is carried out in a solvent made up of the corresponding alkanol as in the alcoholate of alkali metal or alkaline earth metal used. 17. Method as stated in claim 16, characterized in that the initial concentration of the compound of formula (I) in relation to the mixture of the compound of formula (I)/solvent is 3 to 40% by weight, and preferably 10 to 30% by weight %. 18. Procedure as specified in one or more of claims 1 to 17, characterized in that the molar ratio between carbonate of formula (III) or (IV)/copper catalyst is 1 to 50, and preferably 1 to 10. 19. Procedure as specified in one or more of claims 1 to 18, characterized by working at a temperature of 90 to 220°C, and preferably from 100 to 180°C. 20. Use of a method as stated in one or more of claims 1 to 19 for the production of 3,4,5-trimethoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde and 2-hydroxy-5-methoxybenzaldehyde.