Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
1999-04-12
2001-06-12
Keys, Rosalynd (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S421000, C562S407000, C568S432000
Reexamination Certificate
active
06245936
ABSTRACT:
This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR97/01828, filed on Oct. 13, 1997.
The present invention concerns a process for the preparation of a 2-hydroxybenzoic acid and of a 4-hydroxybenzaldehyde and derivatives thereof from a mixture of two phenolic compounds, one carrying a formyl or hydroxymethyl group in the 2 position, and the other carrying a formyl or hydroxymethyl group in the 4 position.
The invention also concerns the preparation of a 4-hydroxybenzaldehyde from said mixture.
The invention more particularly concerns the preparation of 3-methoxy-4-hydroxybenzaldehyde and of 3-ethoxy-4-hydroxybenzaldehyde, respectively known as “vanillin” and ethylvanillin”.
French patent application no. 95/06186 describes a process for the preparation of 4-hydroxybenzaldehydes, and more particularly of vanillin and of ethylvanillin.
The process described consists of preparing a 3-carboxy-4-hydroxybenzaldehyde, then of decarboxylation of said compound, thereby producing 4-hydroxybenzaldehyde.
3-carboxy-4-hydroxybenzaldehyde is prepared according to FR no. 95/06186 from one of the compounds, and mixtures thereof, having more particularly the following formulae (IIa), (IIb), (IIc) and (IId) shown below:
where, in said formulae:
M represents a hydrogen atom and/or a metal cation from group (Ia) or (IIa), or an ammonium cation,
Z
1
, Z
2
and Z
3
, which may be identical or different, represent a hydrogen atom, an alkyl, alkenyl, alkoxy, hydroxyalkyl, alkoxyalkyl, cycloalkyl, or aryl radical, a hydroxy group, a nitro group, a halogen atom, or a trifluoromethyl group.
The patented process starts with a bi-functional phenolic compound carrying on the aromatic ring two functional groups of the hydroxy group, which can be a —CHO group and/or a —CH
2
OH group, at the ortho and para positions.
Firstly, the group in the ortho position is selectively oxidised to the carboxy group; the group in the para position being at the most oxidised to the formyl group. Thus, after eliminating the carboxy group in the ortho position, 4-hydroxybenzaldehyde is obtained.
Vanillin and ethylvanillin are advantageously obtained according to a selective process but one which is also highly competitive industrially as it uses less expensive reactants.
As a result of research, the applicant has found that it is possible a start with a mixture of monosubstituted phenolic compounds.
A process was found, and is object of the present invention, for the preparation of a 2-hydroxybenzoic acid and a 4-hydroxybenzaldehyde and derivatives thereof, which is characterised in that in a mixture of phenolic compounds, one (A) carrying a formyl or hydroxymethyl group in the 2 position, and the other (B) carrying a formyl or hydroxymethyl group in the 4 position, the formyl or hydroxymethyl group in the 2 position of compound (A) is selectively oxidised to a carboxy group and optionally a hydroxymethyl group of compound (B) in the 4 position is selectively oxidised to a formyl group, thus producing a mixture of a 2-hydroxybenzoic acid and a 4-hydroxybenzaldehyde.
In a successive step, the 4-hydroxybenzaldehyde is separated from the reaction medium.
A first variation of the invention consists of separating the 4-hydroxybenzaldehyde from the 2-hydroxybenzoic acid by pH controlled extraction of aldehyde.
Another variation of the invention consists of decarboxylation of only the 2-hydroxybenzoic acid in the mixture obtained, producing the initial phenolic compound which can then be recycled; the 4-hydroxybenzaldehyde is then recovered in a conventional manner.
According to the present invention, it was found that when starting with a mixture of phenolic molecules, one carrying hydroxymethyl or formyl groups in the ortho position of the hydroxyl group and the other carrying a hydroxymethyl or formyl group in the para position of the hydroxy group, oxidation to a carboxy group preferably takes place on the hydroxymethyl or formyl group carried by the (A) molecule, substituted in the ortho position.
The starting substrates used in the process are mixtures of phenolic compounds, one carrying a formyl or hydroxymethyl group in the 2 position and the other in the 4 position.
The term “phenolic compound” denotes any aromatic compound with an aromatic ring which carries a hydroxy group.
In the following description of the present invention, the term “aromatic” denotes the conventional idea of aromaticity as defined in the literature, particularly in “Advanced Organic Chemistry” by Jerry MARCH, 4th edition, John Wiley and Sons, 1992, pp. 40 ff.
Thus, a mixture (II) of phenolic compounds is used, more particularly with the following formulae:
where, in said formulae (IIA) and IIB):
Y
1
and Y
2
, which may be identical or different, represent one of the following groups:
a —CHO group,
a —CH
2
OH group,
Z
1
, Z
2
and Z
3
, which may be identical or different, represent a hydrogen atom, an alkyl, alkenyl, alkoxy, hydroxyalkyl, alkoxyalkyl, cycloalkyl, or aryl radical, a hydroxy group, a nitro group, a halogen atom, or a trifluoromethyl group.
Particularly suitable compounds for use in the process of the invention have formulae (IIA) and (IIB) where Z
1
, Z
2
and Z
3
, which may be identical or different, represent one of the following atoms or groups:
a hydrogen atom,
a linear or branched alkyl radical containing 1 to 12 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl,
a linear or branch alkenyl radical containing 2 to 12 carbon atoms, preferably 2 to 4 carbon atoms, such as vinyl or allyl,
a linear or branched alkoxy radical containing 1 to 12 carbon atoms, preferably 1 to 4 carbon atoms, such as a methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy or tert-butoxy radical,
a phenyl radical,
a halogen atom, preferably a fluorine, chlorine or bromine atom.
The present invention does not exclude the presence on the aromatic cycle of substituents of a different nature, provided that they do not interfere with the reactions taking place in the process of the invention.
The present invention is preferably applicable to compounds with the formulae (IIA) and (IIB) where Z
1
, represents a hydrogen atom or a linear or branched alkyl or alkoxy radical containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms; Z
2
and Z
3
represent a hydrogen atom; and Y
1, and Y
2
are identical and represent a formyl group or a hydroxymethyl group.
Examples of preferred mixtures of phenolic compounds which can be used in the process of the invention are, inter alia:
o-hydroxymethylphenol and p-hydroxymethylphenol,
o-hydroxymethylguaiacol and p-hydroxymethylguaiacol,
o-formylguaiacol and p-formylguaiacol,
o-hydroxymethylguetol and p-hydroxymethylguetol,
o-formylguetol and p-formylguetol.
According to the process of the invention, a mixture of phenolic compounds having preferably formula (II) is used as the starting compound.
The proportion of each hydroxymethylated or formylated phenolic compound in the mixture depends on how they are prepared.
By way of an example, the proportion of each isomer can vary greatly, for example from 10 to 90% by weight, and more preferably between 30 and 70%.
The reaction scheme of the process according to the invention is given below to facilitate comprehension of the disclosure of the invention, without in any way binding the scope of the invention to said scheme.
where, in said formulae (I) to (IV):
Y
1
, and Y
2
, which may be identical or different, represent one of the following groups:
a —CHO group,
a —CH
2
OH group,
M represents a hydrogen atom and/or a metal cation from group (Ia) or (IIa) of the periodic classification, or an ammonium cation,
Z
1
, Z
2
and Z
3
have the meanings given above.
In the present text, references are made hereinafter to the periodic classification of the elements as published in the “Bulletin de la Societe Chirnique de France”, no. 1 (1966).
In accordance with the process of the invention, the Y
1
group in position 2 of a phenolic compoun
Denis Philippe
Maliverney Christian
Metivier Pascal
Keys Rosalynd
Rhodia Chimie
Seugnet Jean-Louis
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