US 2015O183702A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2015/0183702 A1 Garel (43) Pub. Date: Jul. 2, 2015

(54) METHOD FOR PRODUCING Publication Classification ALKOXYPHENOLAND (51) Int. Cl. ALKOXY-HYDROXYBENZALDEHYDE CD7C 45/38 (2006.01) C07C 5 L/353 (2006.01) (71) Applicant: RHODIA OPERATIONS, Paris (FR) CD7C4I/06 (2006.01) (52) U.S. Cl. CPC ...... C07C45/38 (2013.01); C07C4I/06 (72) Inventor: Laurent Garel, Lyon (FR) (2013.01); C07C51/353 (2013.01) (57) ABSTRACT (73) Assignee: RHODIA OPERATIONS, Paris (FR) The invention relates to a method for producing alkoxyphenol from hydroxyphenol, comprising an O-alkylation reaction of (21) Appl. No.: 14/417,015 at least one hydroxyphenol into at least one alkoxyphenol, said reaction being carried out using an O-alkylating agent, an PCT Fled: Jul. 12, 2013 aqueous solvent containing a Bróensted base, and an organic (22) solvent, with a base/O-alkylating agent ratio of between 0.5 and 1.5 in moles of base per mole of O-alkylating agent, an (86) PCT NO.: PCT/EP2013/064861 O-alkylating agent/hydroxyphenol ratio of between 0.5 and 2 moles of O-alkylating agent per mole of hydroxyphenol, and S371 (c)(1), an organic solvent/hydroxyphenol ratio of less than 280 mL. (2) Date: Jan. 23, 2015 preferably between 10 and 250 mL and more preferably still between 50 and 150 mL of organic solvent per mole of (30) Foreign Application Priority Data hydroxyphenol. The invention also relates to a method for producing at least one alkoxy-hydroxybenzaldehyde from at Jul. 26, 2012 (FR) ...... 12572.75 least one hydroxyphenol compound. Patent Application Publication Jul. 2, 2015 Sheet 1 of 2 US 201S/O183702 A1

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METHOD FOR PRODUCING 0011 Processes for synthesizing para-methoxyphenol ALKOXYPHENOLAND (PMP, also known as MEHQ for hydroquinone monomethyl ALKOXY-HYDROXYBENZALDEHYDE ether) from hydroquinone also exist. PMP is used, for example, in industry as a polymerization inhibitor or as an TECHNICAL FIELD OF THE INVENTION antioxidant. 0001. The present invention relates to a process for pro AIMS OF THE INVENTION ducing at least one alkoxyphenol compound from at least one hydroxyphenol. 0012. These routes of access require improvement, and in 0002 The present invention also relates to a process for particular the route of access starting from pyrocatechol and/ producing at least one alkoxyhydroxybenzaldehyde com or from hydroquinone. An aim of the present invention is to pound from at least one hydroxyphenol compound. The manufacture the alkoxyphenol compound industrially with a present invention relates more specifically to a process for good yield, a low production of impurities and/or efficient synthesizing vanillin (VA or 4-hydroxy-3-methoxybenzalde removal thereof, and a high hydroxyphenol conversion, while hyde) and/or ethylvanillin (EVA or 3-ethoxy-4-hydroxyben at the same time limiting the costs of Such a production. An Zaldehyde). The present invention relates in particular to a aim of the invention is in particular to produce this alkox process for producing Vanillin and/or ethylvanillin from a yphenol compound on the basis of an O-alkylation reaction precursor of guaiacol and/or of guaethol, and in particular using an O-alkylating agent. It is thus possible to produce, for from pyrocatechol. example, guaiacol from pyrocatechol, but Veratrole (1.2- dimethoxybenzene) also forms via an additional (Successive) O-methylation reaction of the guaiacol. The processes for PRIOR ART preparing alkoxyphenol according to the invention generate 0003 Alkoxyhydroxybenzaldehydes are very important at least one compound of the dialkoxybenzene type. This products used first as flavorings and fragrances and then Sub compound can be considered to be an impurity, but also sequently as intermediate products in numerous fields, for Sometimes to be an economically exploitable compound. In instance agrochemistry, pharmacy, the cosmetics industry view of the potential benefit of the parallel economic exploi and other industries. tation of the alkoxyphenol and of the compounds of the 0004. In particular, vanillin and ethylvanillin are products dialkoxybenzene type, it is desired to be able to adjust the that are essentially intended for foods. It is therefore impor synthesis preferentially toward one or other of the compounds tant to offer the market products which are of high chemical according to market demand, i.e. to be able to form to a purity and of good taste quality while at the same time ensur greater or lesser extent the compound of the dialkoxybenzene ing a marketing cost that is as low as possible. type compared with the alkoxyphenol, and vice versa. For 0005 Thus, the process for synthesizing said products example, Veratrole can today be exploited separately from requires an improvement in the chemical reactions carried out guaiacol. Thus, the invention aims to provide a process for and the performing of efficient separation and purification producing at least one alkoxyphenol from at least one hydrox operations. yphenol which makes it possible to modulate or adjust the production of the dialkoxybenzene/alkoxyphenol ratio. 0006 Various processes have been proposed for the syn 0013 An aim of the present invention is in particular to thesis of aromatic aldehydes. The most significant processes form the dialkoxybenzene compound, such as 1.2- are based on the functionalization of a starting phenolic com dimethoxybenzene (veratrole), 1,2-diethoxybenzene, 1,4- pound, for example phenol, catechol, catechol derivative, dimethoxybenzene (PDMB), or 1,4-diethoxybenzene, during guaiacol (or 2-methoxyphenol) or guaethol (or 2-ethoxyphe the synthesis of alkoxyphenol. Such as guaiacol, guaethol, nol). In this type of process, the phenolic compound is gen 4-methoxyphenol (PMP) and/or 4-ethoxyphenol (PEP), erally used in a salified form, for example, in the form of a according to a ratio which meets the isolated needs of the Sodium salt: a formyl group is added in the para position with market, i.e. according to a dialkoxybenzenefalkoxyphenol respect to the hydroxyl group present on the benzene ring, ratio of between 0.001 and 0.9, while limiting the costs of an according to various methods. industrial production. An aim of the invention is in particular 0007 To produce guaiacol, some processes consist in to provide Such a process while at the same time maximizing choosing ortho-nitrochlorobenzene (ONCB) as starting the conversion of the starting hydroxyphenol. material. 0014 Moreover, in order to exploit the highly pure alkox 0008. These processes have many drawbacks compared yphenol compound, it is in particular necessary to separate with the process starting from pyrocatechol: handling of the latter from the dialkoxybenzene formed. An aim of the CMR (carcinogenic, mutagenic and toxic to reproduction) present invention is also to remove the dialkoxybenzene com toxic compounds. Such as o-anisidine; numerous steps; exo pound formed after production of at least one alkoxyphenol thermic and dangerous reactions, such as nitration or hydroly from at least one hydroxyphenol. Generally, a dialkoxyben sis of a diazonium salt; generation of a large amount of Zene compound is difficult to separate from an alkoxyphenol effluents; formation of impurities, such as 5-chloroguaiacol, compound. This therefore makes it difficult to obtain the which are in vanillin in the form of 6-chlorovanillin, etc. exploitable alkoxyphenol, i.e. alkoxyphenol which is sepa 0009 Moreover, there is a completely different route for rated in particular from the dialkoxybenzene formed, with a obtaining Vanillin, which consists in reacting guaiacol and satisfactory degree of purity, while at the same time maintain glyoxylic acid in a basic medium, resulting in 4-hydroxy-3- ing industrial production costs which are acceptable for the methoxymandelic acid, and then in oxidizing the condensate market. obtained. 0015 These problems arise more especially during the 0010) Synthesizing guaiacol or guaethol from pyrocat production of Vanillin (VA) or of ethylvanillin (EVA) from echol is much more direct. ortho-hydroxyphenol (or pyrocatechol, termed “PC” in the US 2015/O 183702 A1 Jul. 2, 2015

present invention or else called catechol, or pyrocatechin) been noted in the context of the present invention that the since the “dialkoxylated impurity of guaiacol (GA) or of amount of organic solvent normally used according to the guaethol (GE). Such as, in particular, 1,2-dimethoxybenzene prior art has no influence on the dialkoxybenzene/alkoxyphe (or veratrole) and/or 1,2-diethoxybenzene, is very difficult to nol ratio. However, it has been noted experimentally, Surpris separate from GA and/or GE. The compounds of the ingly, by the inventors that, below a certain amount of organic dialkoxybenzene type. Such as Veratrole, accumulate during solvent per mole of hydroxyphenol under defined reaction the synthesis of alkoxyhydroxybenzaldehydes since they do conditions, the amount of organic solvent influences the not react with glyoxylic acid. It is therefore important to be dialkoxybenzenefalkoxyphenol ratio. Such that it is possible able to separate or remove the dialkoxybenzene compound to modulate or adjust this ratio according to the market from the alkoxyphenol production stream, and therefore also demands and thus to independently exploit the dialkoxyben during the production of alkoxyhydroxybenzaldehydes. Zene and alkoxyphenol compounds, after separation, while at 0016. The same problems arise in terms of performance the same time minimizing the reserves of the compound in and quality of the reaction for O-alkylation of hydroquinone excess with respect to the market needs. to PMP. It is desired to modulate the PDMB/PMP ratio and to 0024. The invention does not broach the separation and the remove the dialkoxylated compound 1,4-dimethoxybenzene exploitation of the dialkoxybenzene compound. (PDMB) from the PMP formed. 0017 Thus, an aim of the invention is also to provide a 0025. The invention thus relates to a process for producing process for producing, from at least one hydroxyphenol, at alkoxyphenol from hydroxyphenol, comprising a reaction for least one alkoxyphenol of high purity from the viewpoint of O-alkylation of at least one hydroxyphenol to give at least one the unwanted presence of dialkoxybenzene compound(s). alkoxyphenol, said reaction being carried out using an 0018 Moreover, the production of vanillin and/or of eth O-alkylating agent, an aqueous solvent comprising a Bröen ylvanillin requires improvement as a whole, in particular sted base, and an organic solvent, with a base/O-alkylating starting from the precursor represented by pyrocatechol. This agent ratio of between 0.5 and 1.5 in moles of base per mole is another independent aim of the process of the invention, as of O-alkylating agent, an O-alkylating agent/hydroxyphenol is the control of the amount of Veratrole and/or of 1,2-di ratio of between 0.5 and 2 mol of O-alkylating agent per mole ethoxybenzene produced during a process for synthesizing of hydroxyphenol, and an organic solvent/hydroxyphenol vanillin and/or ethylvanillin from pyrocatechol. ratio of less than 280 ml, preferably of between 10 and 250 ml, and more preferably of between 50 and 150 ml of organic SUMMARY OF THE INVENTION solvent per mole of hydroxyphenol. 0026. The base/O-alkylating agent, O-alkylating agent/ 0019. The present invention makes it possible to produce hydroxyphenol, and organic solvent/hydroxyphenol ratios the alkoxyphenol compound industrially with a good yield, a according to the invention make it possible to adjust the yield low production of impurities and/or efficient removal thereof, of alkoxyphenol compound and/or of dialkoxybenzene com and a high hydroxyphenol conversion, while at the same time pound, and to adjust the hydroxyphenol conversion, and thus limiting the costs of an industrial production. to optimize them. It is preferred for the amount of organic 0020. The present invention makes it possible to modulate Solvent used to be less than or equal to the maximum amount or adjust the dialkoxybenzene/alkoxyphenol ratio between of organic solvent influencing the dialkoxyphenol/alkox certain values in order to produce the two compounds accord yphenol ratio. The maximum amount of organic solvent influ ing to amounts which meet the momentary needs of the mar encing the dialkoxyphenol/alkoxyphenol ratio depends on ket. the solvent itself and on the precise reaction conditions used. 0021. The present invention also makes it possible to It is preferred for the amount of solvent used to be less than remove the dialkoxylated compound formed during the 280 ml, preferably than 250 ml, and more preferably than 150 alkoxyphenol production. ml, per mole of hydroxyphenol. 0022. The synthesis of alkoxyphenol from hydroxyphenol is known, whether in the gas phase or in a multiphase medium 0027. The invention thus relates to a process for producing by O-alkylation using an O-alkylating agent. In a multiphase guaiacol and/or guaethol from pyrocatechol or for producing medium, it is also known that the base/alkylating agent ratio para-methoxyphenol and/or para-ethoxyphenol from hydro and the alkylating agent/hydroxyphenol ratio make it pos quinone, by O-methylation and/or O-ethylation of one of the sible to influence the dialkoxybenzene/alkoxyphenol ratio. hydroxyl groups of the pyrocatechol or of the hydroquinone. These ratios directly influence the reaction performance lev 0028. The present invention also relates to a process for els, i.e. the degree of conversion of the reagents, the yields of producing alkoxyhydroxybenzaldehyde from hydroxyphe the products formed, and in particular of alkoxyphenol and/or nol, comprising a reaction for O-alkylation of at least one of dialkoxybenzene, and the selectivity of the products hydroxyphenol to give at least one alkoxyphenol, said reac obtained, in particular the dialkoxybenzenefalkoxyphenol tion being carried out using an O-alkylating agent, an aqueous ratio. Solvent comprising a Bróensted base, and an organic solvent, 0023 The inventors have discovered, surprisingly, that a with a base/O-alkylating agent ratio of between 0.5 and 1.5 in medium comprising at least one liquid-liquid phase, and in moles of base per mole of O-alkylating agent, an O-alkylating particular in a three-phase medium, the amount of organic agent/hydroxyphenol ratio of between 0.5 and 2 mol of Solvent also makes it possible to modulate or adjust the O-alkylating agent per mole of hydroxyphenol, and an dialkoxybenzene/alkoxyphenol ratio while at the same time organic solvent/hydroxyphenol ratio of less than 280 ml, preserving very satisfactory, or even optimal, industrial con preferably of between 10 and 250 ml, and more preferably ditions in terms of hydroxyphenol conversion and of yields of between 50 and 150 ml of organic solvent per mole of hydrox the various products. The prior art is, to the inventors knowl yphenol, and said process comprising a reaction which intro edge, silent regarding any influence of the amount of organic duces an aldehyde function on the alkoxyphenol so as to solvent on the dialkoxybenzene/alkoxyphenol ratio. It has obtain the corresponding alkoxyhydroxybenzaldehyde, pref US 2015/O 183702 A1 Jul. 2, 2015

erably by means of a condensation reaction between the in said formula (I): alkoxyphenol and glyoxylic acid, and then oxidation of the compound formed. 0.038 the R group(s), which may be identical or differ 0029. The present invention relates independently to a ent, represent a hydrogen atom, a hydroxyl group, or an process for producing Vanillin and/or ethylvanillin from pyro alkyl or alkoxy group, catechol, comprising a reaction for O-methylation and/or 0039 n is an integer from 0 to 3. O-ethylation of the pyrocatechol to give guaiacol and/or gua ethol, said reaction being carried out using an O-alkylating 0040. The respective position of the two hydroxyl groups agent, an aqueous solvent comprising a Bröensted base, and of formula (I) is not therefore fixed. an organic solvent, with a base/O-alkylating agent ratio, an O-alkylating agent/hydroxyphenol ratio and an organic Sol 0041 They may be in the ortho, meta or para position. Vent/hydroxyphenol ratio as defined above, said process com 0042 Among the compounds of formula (I), mention may prising a reaction which introduces an aldehyde function on be made of pyrocatechol (“PC” or ortho-hydroxyphenol), the guaiacoland/or the guaetholso as to obtain Vanillin and/or resorcin (“RS' or meta-hydroxyphenol) and hydroquinone ethylvanillin, preferably by means of a condensation reaction (“HQ or para-hydroxyphenol), which are preferred for the between the guaiacol and/or the guaethol and glyoxylic acid, process according to the invention. and then oxidation of the condensation product. This specific sequence makes it possible to produce Vanillin and/or ethyl 0043. In the context of the invention, the term “alkyl is vanillin industrially with a good yield, a low production of intended to mean a linear or branched hydrocarbon-based impurities and/or efficient removal thereof, and a high pyro chain having from 1 to 12 carbonatoms and preferably from catechol conversion. 1 to 4 carbon atoms. Preferred examples of alkyl groups are 0030. In the figures: methyl, ethyl, propyl, isopropyl and tert-butyl groups. 0031 FIG. 1 represents a block diagram of a preferred variant of the process for producing alkoxyphenol from 0044) The term “alkoxy' is intended to mean an—O-alkyl hydroxyphenol; group in which the term “alkyl has the meaning given above. 0032 FIG. 2 represents a block diagram of a preferred Preferred examples of alkoxy groups are methoxy or ethoxy variant of the production of alkoxyhydroxybenzaldehyde groups. from alkoxyphenol; 0045. The term “alkoxyphenol is intended to mean at 0033 FIG.3 represents a block diagram according to a least one compound of benzene type comprising a hydroxyl preferred variant comprising the removal of a dialkoxyben group and an alkoxy (or O-alkyl) group. It corresponds more Zene compound prior to the reaction of the alkoxyphenol with particularly to the formula (II) below: glyoxylic acid. 0034. The dashed lines represent, in particular, preferred variants of the process of the invention. (II) DETAILED DESCRIPTION OF THE INVENTION 0035. The process of the invention applies quite particu larly to the production of alkoxyhydroxyphenols such as guaiacol and/or guaethol, or 1.4-methoxyphenol (para-meth oxyphenol or PMP) and/or 1,4-ethoxyphenol (para-ethox yphenol or PEP), but it is also suitable for other alkoxyhy droxyphenols. in said formula (II): 0036. The process of the invention applies quite particu 0046 R represents an alkyl group, preferably compris larly to vanillin and to ethylvanillin, but it is also suitable for other aromatic aldehydes. ing from 1 to 4 carbon atoms, covalently bonded to the 0037. The term “hydroxyphenol is intended to mean at OXygen atom; least one compound of benzene type, which is Substituted or 0047 R and nareas defined above with reference to the unsubstituted, comprising two hydroxyl groups. The hydrox compound of formula (I). yphenol may be substituted, for example, with one or more groups selected from: hydroxyl, alkyl, alkoxy, halogen, nitro 0048. The alkoxyphenol compounds are produced from and aryl, the groups comprising carbon atoms possibly com the corresponding hydroxyphenol compound, i.e. the R prising one or more heteroatoms, in particular selected from group, provided by an O-alkylating agent, replaces a hydro O, N and S. It corresponds more particularly to formula (I) gen of one of the hydroxyl groups of the starting hydroxyphe below: nol compound. This reaction is called an O-alkylation reac tion. 0049 Mention may in particular be made of guaiacol, (I) guaethol, para-methoxyphenol (PMP) and para-ethoxyphe nol (PEP). 0050. The term “alkoxyhydroxybenzaldehyde' is intended to mean at least one phenyl compound comprising a hydroxyl group, an alkoxy (or O-alkyl) group, and a formyl group. It corresponds more particularly to the formula (III) below: US 2015/O 183702 A1 Jul. 2, 2015

ably between 5 and 10 bar. The invention also covers the (III) presence of another phase, for instance the presence of one or more solids, such as one or more Supported catalysts. 0064. According to another embodiment, the O-alkylating agent is present at least in Solid form (S/L/L three-phase reaction). The O-alkylating agent is preferably selected from an alkyl carbonate or an alkyl sulfate, and preferably from dimethyl sulfate, dimethyl carbonate, diethyl sulfate, diethyl carbonate, and any mixture thereof. 0065 For the O-alkylation reaction, the basic agent (or base) is preferably selected from: an alkali metal or alkaline R, R and n are as defined above with reference to the com earth metal hydroxide, an ammonium hydroxide and an alky pound of formula (I). lammonium hydroxide, and preferably from Sodium hydrox 0051. The alkoxyhydroxybenzaldehyde preferentially ide, potassium hydroxide and an alkali metal carbonate or used in the process of the invention corresponds to the for bicarbonate, and preferably a sodium or potassium carbonate, mula (III) in which R represents a methyl or ethyl group and and any mixture thereof. n=0. 0.066 An O-alkylating agent/hydroxyphenol ratio of 0052. As more specific examples of alkoxyhydroxyben between 0.5 and 2 mol of O-alkylating agent per mole of Zaldehyde, mention may in particular be made of: hydroxyphenol, and more preferably of between 0.7 and 1.7, 0053 vanillin, is preferably used. 0054 ethylvanillin (3-ethoxy-4-hydroxybenzalde 0067. The amount of water added can be quite high and hyde), can range from 0.5 mol of water per mole of hydroxyphenol 0055 isovanillin (3-hydroxy-4-methoxybenzalde up to 30 mol of water per mole of hydroxyphenol, and is hyde), preferably 4 to 30 mol of water per mole of hydroxyphenol. 0056 o-vanillin (2-hydroxy-3-methoxybenzaldehyde), However, it is not solely important to adjust the amount of 0057 syringic aldehyde (3,5-dimethoxy-4-hydroxy water according to the amount of hydroxyphenol. Advanta benzaldehyde). geously, the O-alkylation of the hydroxyphenol to give alkox yphenolina basic multiphase medium has an organic solvent/ O-Alkylation Reaction water ratio, by weight/weight, of less than 1.5, and preferably less than 1.2, and more preferably ranging from 0.05 to 0.8. 0058 According to the present invention, the hydroxyphe 0068 For the O-alkylation reaction, the organic solvent is nol compound can be converted into monoalkoxylated selected so as to extract the alkoxyphenol compound from the derivatives, i.e. into alkoxyphenol, by reaction with an aqueous phase as said compound is formed and to partially O-alkylating agent. solubilize the O-alkylating agent, and to thus limit the forma 0059. The O-alkylating agent is advantageously selected tion of the dialkoxybenzene compound in order to preserve a from compounds which provide an alkyl group as a replace satisfactory dialkoxybenzene/alkoxyphenol ratio. The ment for the hydrogen atom bonded to the oxygen of the organic solvent is also selected so as to partially solubilize the hydroxyphenol compound. Among the various O-alkylating O-alkylating agent in the organic solvent and to thus limit the agents, mention may in particular be made of methylating degradation of the O-alkylating agent on contact with the base agents and ethylating agents which make it possible to give present in aqueous solution, in particular so as to increase the the corresponding methoxylated and/or ethoxylated com O-alkylation yield of alkoxyphenol compound. The organic pounds. solvent is preferably selected from: a linear, branched or 0060 According to one variant of the invention, the pyro unbranched, or cyclic alkane comprising from 5 to 10 carbon catechol, the resorcinol or the hydroquinone is converted to atoms, for example cyclopentane, cyclohexane, methylcyclo the monoalkyl ether thereof by reacting the hydroxyphenol hexane, cycloheptane, n-heptane, octane, a halogenated with an alkyl chloride, preferably having from 1 to 4 carbon alkane Such as dichloroethylene or dichloropropylene, an atOmS. aliphatic alcohol. Such as methanol, an organic solvent com 0061 According to one variant, the process of the present prising from 2 to 10 carbon atoms and an ether function, for invention consists of the production of guaiacol and/or of example diethyl ether, diisopropyl ether, methyl (tert-butyl) guaethol from pyrocatechol or the production of para-meth ether, a solvent comprising from 2 to 10 carbon atoms and a oxyphenol and/or of para-ethoxyphenol from hydroquinone, ketone function, for example acetone and diethyl ketone, by O-methylation and/or O-ethylation of one of the hydroxyl methyl isobutyl ketone, a polyol. Such as a glycol or a poly groups of the pyrocatechol or of the hydroquinone. (ethylene glycol), an aromatic solvent comprising from 5 to 0062) Advantageously, the hydroxyphenol is introduced 12 carbon atoms, for example toluene, Xylenes, benzene and into the alkylation reactor in the form of an aqueous solution. ethylbenzene. Solvents of food quality may be used. 0063. According to one preferred variant of the invention, 0069. It is known, moreover, how to prepare compounds the reaction is carried out in a gas-liquid-liquid three-phase of hydroxyphenol type. The hydroxyphenol is prepared, for medium. According to this variant, the O-alkylating agent is example, by hydroxylation of phenol. The hydroxyphenol is present at least in the gas phase (G/L/L three-phase reaction). advantageously added in liquid form. Thus, the hydroxyphe The O-alkylating agent is preferably selected from an alkyl nol is preferably dissolved in an aqueous medium prior to the halide and preferably a methyl, ethyl, propyl, isopropyl. O-alkylation reaction. butyl, isobutyl, tertiary butyl, amyl, sec-amyl, isoamyl or 0070 According to one preferred variant, the reactor in amyl chloride or bromide. The pressure of the O-alkylation which the O-alkylation reaction is carried out comprises a reaction is advantageously between 3 and 15 bar, and prefer means for introducing a solution of at least one hydroxyphe US 2015/O 183702 A1 Jul. 2, 2015

nol into the reactor, a means for introducing at least one I0081. In the interests of simplicity, no reference is made O-alkylating agent into the reactor, a means for introducing at here to the dialkoxybenzene compound formed. Dialkoxy least one basic aqueous Solution into the reactor, a means for benzene is formed when alkoxyphenol is synthesized. introducing at least one organic solvent into the reactor, and at I0082. The compound of main interest, i.e. the alkoxyphe least one means for removing the reaction mixture compris nol (advantageously the GA and/or GE or PMP and/or PEP) ing in particular the alkoxyphenol and the dialkoxybenzene is essentially in the organic phase. The invention makes it formed. According to one variant, water is introduced into the possible to prepare two principal qualities: in particular guai reactor in addition to the water present in the base introduced acol and/or guaethol in liquid form, and guaiacol and/or gua (basic solution) and to the hydroxyphenol (hydroxyphenol ethol in solid form. Solution). I0083. The acidification (step (c)) of the reaction medium 0071. The reaction conditions fixed by the process of the after O-alkylation is preferably carried out by adding an inor present invention make it possible very advantageously to ganic acid. Acidification is preferably carried out with Sulfu obtain, in particular for the synthesis of guaiacol, a Veratrole? ric acid. The aim of this acidification is to transfer the alkox guaiacol ratio of between 0.001 and 0.9, while at the same yphenolate formed (advantageously guaiacolate and/or time maximizing the degree of conversion of the catechol, guaetholate or para-methoxyphenolate and/or para-ethox industrially, while limiting the production costs, and the yphenolate), present in the basic aqueous phase, into the impurities formed. organic phase in the form of alkoxyphenol (guaiacol and/or 0072 The reaction conditions fixed by the process of the guaethol). present invention make it possible very advantageously to I0084. The step of separation (step d) of the alkoxyphenol obtain, in particular for the synthesis of PMP, a PDMB/PMP from the hydroxyphenol, and of separation of the alkoxyphe ratio of between 0.001 and 0.9, while at the same time maxi nol from the organic solvent, preferably comprises a settling mizing the degree of conversion of hydroquinone, industri out of the acidified reaction medium resulting from the ally, while limiting the production costs, and the impurities O-alkylation and a separation of the organic and aqueous form. phases. The organic phase, i.e. the organic Solvent-alkox 0073. The reaction gives the alkoxyphenol with a very yphenol mixture, is distilled so as to separate the alkoxyphe good yield. nol compound from the organic solvent, and is then dehy 0074 The temperature of the O-alkylation reaction is pref drated (removal of the water). According to one preferred erably between 80 and 150° C. and preferably between 100 variant, the organic solvent used in step d) may be identical to and 140° C. the one used in step b) and may therefore advantageously be 0075. The reaction is preferably carried out in an auto recycled so as to be used in the O-alkylation step and/or in the clave. aqueous-phase treatment step. 0076. The pH of the aqueous phase during the O-alkyla I0085. The aqueous phase may advantageously be treated tion reaction is preferably between 8 and 12. so as to recover the hydroxyphenol (in particular PC or HQ), 0077. The residence time or the reaction time is between and the possible residues of alkoxyphenol compound (GA 15 minutes and 3 hours and preferably between 30 and 90 and/or GE or PMP and/or PEP). This treatment preferably minutes. comprises an extraction of the aqueous phase with an organic solvent, preferably with the same solvent as the one used for 0078. The invention covers in particular the production of the O-alkylation reaction. The organic phase obtained follow guaiacol and/or of guaethol for use thereof in the synthesis of ing this separation may advantageously be added to the vanillin and/or of ethylvanillin. Reference is therefore in par ticular made to the production of guaiacol (GA) and/or of organic phase obtained after separation of the aqueous phase. guaethol (GE), but the invention covers the production of any I0086. The separation according to step (d) of the process alkoxyphenol and mixtures thereof, and in particular the pro of the invention advantageously comprises the following duction of para-methoxyphenol (PMP) and/or para-ethox steps: yphenol (PEP). The invention specifically covers the produc (e) settling out of the aqueous and organic phases and/or tion of guaiacol and/or of guaethol from pyrocatechol. extraction of the residual alkoxyphenol (GA and/or GE or 0079 More particularly, and reference may be made to PMP and/or PEP) in the aqueous phase with an organic sol FIG. 1, the process for producing the alkoxyphenol (advan vent; tageously GA and/or GE or PMP and/or PEP) comprises the (f) distillation of the organic phase comprising the organic following steps: solvent and the alkoxyphenol (advantageously GA and/or GE (a) optional pre-dissolution of the solid hydroxyphenol (ad or PMP and/or PEP) and recycling of the organic solvent; Vantageously catechol (PC) or hydroquinone (HQ)) in an (g) removal of the water (dehydration) from the mixture con aqueous medium; taining the alkoxyphenol (advantageously GA and/or GE or (b) O-alkylation of hydroxyphenol (PC ou HQ) to give alkox PMP and/or PEP); yphenol (advantageously GA and/or GE or PMP and/or PEP) (h) distillation of the reaction crude so as to separate the in a basic multiphase (preferably G/L/L three-phase) alkoxyphenol compound, the dialkoxybenzene compound medium; and the tars (cf. below step h). (c) acidification of the resulting mixture; I0087 Advantageously, steps e) to g) are carried out con (d) separation of the alkoxyphenol from the hydroxyphenol, tinuously, with the exception optionally of the settling out. and separation of the alkoxyphenol from the organic solvent, I0088. After the dehydration step (g), the process of the and recovery at least of the alkoxyphenol compound. invention may comprise a "discontinuous Zone comprising a 0080. These steps can be carried out continuously or semi step of distillation of the alkoxyphenol (advantageously GA continuously or batchwise. and/or GE or PMP and/or PEP) so as to purify it. US 2015/O 183702 A1 Jul. 2, 2015

0089. The process is therefore advantageously continu this aspect. Those skilled in the art are able to know when they ous, with the exclusion optionally of the distillation of the are in the presence of the Salified or nonsalified compound, in alkoxyphenol (advantageously GA and/or GE or PMP and/or particular in the light of the cited literature and of their general PEP). knowledge. 0090 The process may comprise a steph) of distillation of 0098. The aldehyde function is advantageously provided the reaction crude, i.e. the organic phase, the organic Solvent according to two main reactions, namely a condensation of of which has been removed, is distilled so as to separate the the alkoxyphenol compound with glyoxylic acid and the oxi alkoxyphenol compound, the dialkoxybenzene compound dation of the compound resulting from the condensation reac and the tars. The latter may be treated so as to recover the tion. hydroxyphenol which has not reacted during the reaction, 0099. According to one preferred embodiment, the pro which can thus be recycled. The dehydration (g) of the crude cess of the invention also comprises the following steps: alkoxyphenol (GA and/or GE or PMP and/or PEP) is there 0.100 condensation of the alkoxyphenol compound fore preferably followed by a distillation (steph) in order to with glyoxylic acid so as to obtain the corresponding separate the alkoxyphenol compound (GA and/or GE or PMP mandelic compound; and/or PEP) from the other organic compounds present, such 0101 separation of the alkoxyphenol compound from as the possible residues of the hydroxyphenol compounds the solution containing the mandelic compound, prefer (unreacted reagent) and dialkoxybenzene, and from the tars ably with recycling of the alkoxyphenol compound; (dimers, trimers, oligomers, and other organic compounds of 0102 oxidation of the mandelic compound so as to very high molecular weight). obtain the alkoxyhydroxybenzaldehyde; 0091. The hydroxyphenol (unreacted reagent) is more 0.103 separation of the alkoxyhydroxybenzaldehyde by preferably separated from the tars by means of a treatment extraction with an organic Solvent, then separation of the known to those skilled in the art. The hydroxyphenol is pref alkoxyhydroxybenzaldehyde from the organic solvent, erably recycled for the O-alkylation step. The invention preferably with recycling of the alkoxyhydroxybenzal makes it possible to maximize the conversion of the hydrox dehyde extraction organic solvent; and yphenol while at the same time minimizing the production 0.104 recovery of the alkoxyhydroxybenzaldehyde, COStS. optionally in Solid form. 0092. The dialkoxybenzene (veratrole and/or 1,2-diethy 0105. When “mandelic”, “vanillin' or “ethylvanillin' is oxybenzene, or 1,4-dimethyoxybenzene and/or 1,4-diethy mentioned without further information, the para-mandelic oxybenzene) can advantageously be exploited by treating it compound, para-Vanillin or ethyl-para-vanillin is respec by means of an additional purification step, known to those tively targeted, unless otherwise indicated. skilled in the art, such as a distillation, or a step of Washing 0106 The para-mandelic compounds (formula (IV)), in procedure(s), or other purification techniques. In accordance particular the production of para-Vanillin, have the following with the invention, the amount of organic solvent used should preferably be less than or equal to the maximum amount of formulae: organic solvent influencing the dialkoxyphenol/alkoxyphe nol ratio in order to be able to vary the dialkoxybenzene/ (IV) alkoxyphenol ratio and to limit the dialkoxybenzene and OH alkoxyphenol reserves in excess with respect to the market needs. 0093. The invention also covers the production of at least rts OR (R)n-- - - one alkoxyhydroxybenzaldehyde from hydroxyphenol. 2 0094 Synthesis of alkoxyhydroxybenzaldehyde 0095. The process according to the invention makes it possible to produce an alkoxyhydroxybenzaldehyde by add HO CO2H ing an aldehyde function to the abovementioned alkoxyphe OH nol compound. 0096. The process according to the invention makes it OMe possible to produce in particular vanillin and/or ethylvanillin from guaiacol and/or guaethol. The guaiacol/guaethol mix ture is obtained in any proportions. The GA/GE ratio depends on the O-alkylation conditions. This GA/GE weight ratio may, for example, range from 0.1/100 to 100/1. The vanillin/ HO CO2H ethylvanillin weight ratio preferably ranges from 80/20 to mandelic compound of para-Vanillin 40/60, or preferably from 80/20 to 45/55. According to one variant, the Vanillin/ethylvanillin molar ratio is at least equal to 2. Preferably, the proportion of Vanillin by weight is 0107 Preferably, the steps and their sequence are carried between 65% and 72%, and preferably between 60% and out continuously, with the exception of a few steps as during 70%, and the proportion of ethylvanillin is between 28% and the separation of the compounds. 35%, and preferably between 30% and 33% by weight. 0108. The reactions for condensation of the alkoxyphe 0097. Reference is made to the alkoxyphenol, guaiacol nols, and in particular of guaiacol, with glyoxylic acid are and guaethol compounds, and to the corresponding alkoxy described in the literature. Mention will quite particularly be hydroxybenzaldehydes independently of their salified or non made of patents EP 0 578 550, WO 99/65853 and WO salified form. When reference is explicitly made to the salt, 09077383, to which reference is made for the production of this makes it possible to describe a particular detail regarding the compounds of the invention. US 2015/O 183702 A1 Jul. 2, 2015

0109 The sequence of the above steps can be carried out 0116 succession of steps a) to d) (and preferably according to the following reactions according to the example including steps e) to h) described above in particular guaiacol: with reference to FIG. 1), so as to recover at least one Condensation of guaiacol and of glyoxylic acid so as to form alkoxyphenol; para-mandelic acid: 0.117 condensation of the alkoxyphenol (AP) com guaiacol-glyoxylic acid--NaOH-guaiacolate-man pound with glyoxylic acid so as to obtain the corre delate(phenate)+H2O sponding mandelic compound, after the addition of water, of glyoxylic acid and of a base; Acidification so as to recover the unreacted guaiacol: 0118 separation of the alkoxyphenol compound from guaiacolate-mandelate(phenate)+-guaiacol-mande the Solution containing the corresponding mandelic late--Na2SOH2SO compound, after the addition of an organic solvent and of an acid, preferably with recycling of the alkoxyphenol Oxidation of the para-mandelic acid so as to form para-van compound; illin: 0119) oxidation of the mandelic compound by reaction with an oxidizing agent introduced so as to obtain the mandelate--NaOH--O-->vanillate--Na2CO+H2O corresponding alkoxyhydroxybenzaldehyde; Acidification so as to form Vanillin: 0120 separation of the alkoxyhydroxybenzaldehyde by extraction after the addition of an organic solvent and of an acid: 0110. During the separation of the mixture, whether it is of 0121 separation of the alkoxyhydroxybenzaldehyde the alkoxyphenol or of the alkoxyhydroxybenzaldehyde, hav from the organic solvent by distillation, preferably with ing resulted in their formation, a recycling, also called a loop, recycling of the organic solvent; and is preferably carried out. Thus, in the present invention, ref 0.122 recovery of the alkoxyhydroxybenzaldehyde erence is made to “recycling loop 1 when referring to the recycling of the excess alkoxyphenol during the condensation (AHBA), optionally in solid form. reaction, and to “recycling loop 2 when referring to the (0123 Condensation Reaction recycling of the alkoxyhydroxybenzaldehyde extraction sol 0.124. According to one advantageous variant, the alkox vent, during the separation steps. yphenol is reacted with glyoxylic acid in the presence of an inorganic base and of an organic base, and preferably NaOH 0111. Once separated, the alkoxyhydroxybenzaldehyde or KOH, and more preferably in the presence of sodium may be treated so as to obtain it in solid purified form; refer hydroxide (NaOH), or ammonium hydroxide. According to ence is made in the present invention to “solid chain'. This treatment can typically implement the steps of crystallization, this variant, a mixture of alkyl phenolate and of derivative of pulling dry, and drying, or flaking. Among these steps, some, the mandelate type is obtained. like the pulling dry, may not be carried out continuously. 0.125. The condensation reaction between the alkoxyphe Thus, the process is preferably continuous, with the exclusion nol (in phenolate form) and glyoxylic acid allows the synthe of the pulling dry. sis of the corresponding para-mandelic acid. 0.126 The condensation can be carried out in a cascade of 0112 The vanillin and/or the ethylvanillin thus obtained stirred reactors. According to one variant, the reaction is may in particular be used as a flavoring in industry, for carried out in a piston flow reactor, optionally comprising a instance in the food, pharmaceutical or cosmetics industry, in heat exchanger. Such an embodiment is, for example, particular for example for manufacturing fragrances. described for guaiacol in application WO 09/077383. The 0113. The vanillin and/or the ethylvanillin may also be condensation reaction between the alkoxyphenol and glyoxy used as a synthesis intermediate, for example for the produc lic acid can be carried out in water, in the presence of an alkali tion of Veratric aldehyde (3,4-dimethoxybenzaldehyde) and/ metal, said reaction being carried out in a piston flow reactor. or 3,4-diethoxybenzaldehyde. It can be carried out in a tubular reactor. 0114. In this context, if the process relates to the simulta I0127. The condensation reaction can advantageously be neous production of vanillin and of ethylvanillin, it is possible catalyzed by a quaternary ammonium hydroxide, for instance either to synthesize the vanillin and ethylvanillin according to according to the reaction described in patent application EPO the same stream, from a stream comprising guaiacol and 578 550. guaethol, themselves prepared from catechol by simulta I0128. The condensation reaction can advantageously be neous reaction with an O-methylating agent and an O-ethy carried out in the presence of a dicarboxylic acid, for instance lating agent; or to synthesize guaiacol and guaethol sepa according to the reaction described in patent application WO rately and then to mix them before the condensation step so as 99765853. to synthesize the Vanillin and ethylvanillin according to the I0129. Since the alkoxyphenol is usually in excess with same stream; or to synthesize the mandelic compounds sepa respect to the glyoxylic acid, the alkoxyphenol fraction which rately via separate reactions of the guaiacol and of the gua has not reacted is advantageously recovered from recycling ethol with glyoxylic acid and then to mix the corresponding loop 1. This excess reduces the probability of forming com mandelic compounds before the oxidation step; or to synthe pounds of the dimandelic acid type (i.e. compounds resulting size the vanillin and ethylvanillin separately and then to mix from the condensation of two glyoxylic acid molecules with them, for example before the crystallization. one guaiacol molecule). 0115 Thus, it is possible to represent the reaction scheme 0.130 Advantageously, firstly, the alkoxyphenol and according to FIG. 2 which advantageously comprises the sodium hydroxide react to form sodium alkoxyphenolate. For following steps: example for guaiacol: US 2015/O 183702 A1 Jul. 2, 2015

alkoxyphenolate into alkoxyphenol under conditions which CHO CHO keep the mandelate in salified form. 0145 The unreacted alkoxyphenol, present in the organic phase, can be separated from the mandelate formed, present HO -O + NaOH -- O + H2O in the aqueous phase. 0146 According to one variant, the alkoxyphenol obtained after neutralization can be extracted by extraction 0131 Then the alkoxyphenolate reacts with glyoxylic acid via the addition of an organic solvent which solubilizes the to form the corresponding para-mandelate: alkoxyphenol contained in the aqueous phase. Reference is made here, for example, to the process described for guaiacol in patent FR 2379 501. CHO,-COOH + NaOH -- CHO-COONa + H2O 0147 According to one preferred embodiment, the alkox yphenol contained in the aqueous phase is extracted with an CHO organic solvent. Use is made of an organic solvent which is inert with respect to the mandelate. As solvents which can be NaO | CHO COONa - - used, mention may in particular be made of halogenated or nonhalogenated aliphatic, cycloaliphatic or aromatic hydro CHO carbons; alcohols; ethers; ketones and nitriles. As aliphatic, cycloaliphatic or aromatic hydrocarbons, mention is more particularly made of heptane, cyclohexane, methylcyclohex NaO CHOH-COONa ane, benzene and toluene; as halogenated aliphatic, cycloaliphatic or aromatic hydrocarbons, mention is more particularly made of dichloromethane, trichloromethane, 0132) These two reactions for preparing the glyoxylate dichloroethane, chlorobenzene and dichlorobenzenes; as and the guaiacolate can be carried out according to two sepa alcohols, mention is more particularly made of methanol, rate steps. Alternatively, the glyoxylic acid is brought into ethanol, propanol, isopropanol and butanol; as ethers, men contact directly with the guaiacolate in the presence of the tion is more particularly made of diethyl ether, diisopropyl base. ether and methyl (tert-butyl) ether; as ketones, mention is 0.133 Alkoxyphenolate Solution more particularly made of acetone, methyl ethyl ketone, 0134. According to one advantageous variant, an alkox methyl isobutyl ketone and diisobutyl ketone; and as nitriles, yphenolate solution is prepared. This alkoxyphenolate solu mention is more particularly made of acetonitrile. A mixture tion is fed with alkoxyphenol from a storage tank which of said solvents may be used. A solvent of food quality may be receives the alkoxyphenol recycled from recycling loop 1 and used. the new alkoxyphenol. This alkoxyphenolate Solution is 0.148. The mandelate then remains in the aqueous phase, advantageously introduced into the reactor for the condensa whereas the alkoxyphenol goes into the organic phase. tion reaction. 014.9 The alkoxyphenol to be recycled may be contami 0135 All of the (demineralized) water and of an inorganic nated by the presence of organic solvent residues. The pres base (for example sodium hydroxide) required for the reac ence of organic solvent in the alkoxyphenol results in a sig tion are fed into the alkoxyphenolate solution. nificant decrease in the performance levels of the 0136. The temperature of the reactor for preparing the condensation reaction. It is therefore preferable to separate alkoxyphenolate Solution is advantageously maintained at the the extraction solvent from the alkoxyphenol before its rein condensation reaction temperature. troduction into the alkoxyphenol storage tank. 0137 Recycling Loop 1 0150. After separation of the aqueous and organic phases, 0138 Recycling loop 1 is the recovery of the alkoxyphe the alkoxyphenol-organic phase mixture is preferably dis nol which has not reacted in the condensation reaction. Thus, tilled so as to separate the organic solvent from the alkox loop 1 relates to the separation of the alkoxyphenol com yphenol, and also from tars generally present, in order to pound from the mandelic compounds, which advantageously recycle the organic solvent. comprises the following steps: 0151. Other types of separation may be envisioned. 0.139 recovery of a mixture comprising the mandelic 0152 The aqueous phase containing the mandelate is pref compound formed in mandelate form and the unreacted erably treated so as to remove the residual organic solvent, for alkoxyphenol in alkoxyphenolate form; example by distillation. The mandelate then feeds the oxida 0140 neutralization of the alkoxyphenolate to give the tion reaction. alkoxyphenol, while maintaining the corresponding 0153. According to one variant, the unreacted alkoxyphe mandelate in conjugated base (Salified) form; nolate can be separated using basic anion exchange resins or 0141 separation of the alkoxyphenol from the mande an adsorbent resulting in selective binding of the alkoxyphe late: nol and in the recovery of an aqueous stream comprising the 0.142 introduction of the mandelate into an oxidation mandelic compounds in Salified form resulting from the con reactor; and densation reaction. The stream of the alkoxyphenol in salified 0.143 recycling of the alkoxyphenol, which has not form (alkoxyphenolate) bound to the resin or the adsorbent reacted as a reagent, to the condensation reaction. can be separated by means of a resin regeneration treatment or 0144. The reaction medium resulting from the condensa a desorption treatment. Such separation methods are in par tion is advantageously neutralized with an inorganic acid, and ticular described in patent applications WO 09/141280 and preferably with sulfuric acid, so as to convert the unreacted WO 11 FO393.31. US 2015/O 183702 A1 Jul. 2, 2015

0154 The alkoxyphenol which has not reacted during the also comprises the preparation of an aqueous solution of condensation reaction is preferably recycled to the feed of the alkoxyphenol in Salified (phenolate) form, and the separation alkoxyphenolate solution. of the residual dialkoxybenzene from the aqueous mixture comprising the alkoxyphenoate. Removal of the Dialkoxybenzene (Called “DAB”) Possibly 0162 According to one preferred variant, illustrated for Present example according to FIG. 3, the process comprises the fol 0155 As was indicated above, the O-alkylation reaction lowing steps: also generates a dialkoxybenzene compound. In the process 0.163 preparation of a solution of alkoxyphenol (AP) of the invention, the alkoxyphenol obtained after the O-alky for example in a mixture made up of a new alkoxyphenol lation reaction is therefore in a mixture with a Super alkoxy with an alkoxyphenol originating from recycling, said lation (dialkoxylation) compound of the dialkoxybenzene Solution of alkoxyphenol also comprising an impurity of type. the dialkoxybenzene (DAB) type: 0156. It has in particular been discovered by the inventors 0.164 preparation of a solution of alkoxyphenolate by that, when Veratrole (1,2-dimethoxybenzene) is formed, in adding water and at least one base to the solution of particular when guaiacol has been prepared from pyrocat alkoxyphenol; echol, the Veratrole accumulates in the guaiacol Solution 0.165 separation of the dialkoxybenzene from the owing to the recycling, but also because it does not react alkoxyphenol; during the condensation reaction with glyoxylic acid. 0166 optional exploitation of the dialkoxybenzene: 0157. The veratrole concentration in the guaiacol storage 0.167 condensation of the alkoxyphenol with glyoxylic tank (mixture of new-recycled) is variable. Since veratrole acid and obtaining of the corresponding mandelic com does not react in the condensation reactions according to the pound, which is for example Salified (mandelate). invention, Veratrole therefore has a tendency to accumulate in 0168 According to one variant, the separation of the the guaiacol solution and thus reduces the guaiacol titer in the dialkoxybenzene from the alkoxyphenol is carried out by Solution injected into the condensation reactor. In the process distillation or settling out. of the invention, it is sought to limit the veratrole accumulated 0169 Advantageously, the mandelic compounds are in the guaiacolor the guaiacolate solution. Thus, according to obtained in salified form. Thus, the process of the invention one preferred embodiment of the invention, the dialkoxyben comprises a step of neutralization of the Salified mandelic Zene formed is removed. According to one variant of the compound to give the mandelic compound in acid form. process of the invention, the Veratrole concentration by 0170 According to one variant, the hydroxyphenol is weight in the Solution comprising AP before the condensation pyrocatechol, the alkoxyphenol is the guaiacol obtained in reaction is between 0.01% and 25% and preferably between step (i) with a methylating agent, and the dialkoxybenzene is 0.01% and 10%, and more preferably between 0.01% and Veratrole, and the process also comprises the separation, in 5%, and is generally approximately 2%. step (iii), of the pyrocatechol from the guaiacol and Veratrole 0158. The invention therefore relates to an independently mixture. patentable process for producing at least one alkoxyhydroxy 0171 According to one variant, the hydroxyphenol is benzaldehyde compound from at least one hydroxyphenol pyrocatechol, the alkoxyphenol is the guaethol obtained in compound, said process being characterized in that it com step (i) with an ethylating agent, and the dialkoxybenzene is prises: 1.2-diethoxybenzene, and the process also comprises the (i)—the synthesis of at least one alkoxyphenol from at least separation, in step (iii), of the pyrocatechol from the guaethol one hydroxyphenol in the presence of at least one O-alkylat and 1,2-diethoxybenzene mixture. ing agent, 0172 Advantageously, a part of the alkoxyphenol (alkox (ii)—the recovery of at least one alkoxyphenol and of impu yphenolate) is advantageously diverted to a distillation col rities, including a dialkylated compound of the dialkoxyben umn intended to limit the dialkoxybenzene content in the Zene type (also called here “DAB); guaiacol before the condensation reaction. The dialkoxyben (iii)—the separation of the dialkoxybenzene from the alkox Zene is distilled at the top in the form of a dialkoxybenzene yphenol; water heteroazeotrope. A temperature at the bottom of the (iv)—the condensation of the alkoxyphenol with glyoxylic distillation column of between 90 and 120° C. is preferred. acid and the obtaining of the corresponding mandelic com This process makes it possible, for example for guaiacol, to pound; limit the veratrole concentration by weight to 0.01% in the (V)—the oxidation of the mandelic compound to give the guaiacol (or guaiacolate) used for the condensation reaction. corresponding alkoxyhydroxybenzaldehyde; and 0173 The dialkoxybenzene-water heteroazeotrope is then (vi)—the recovery of the alkoxyhydroxybenzaldehyde advantageously separated by settling out or another means of optionally in Solid form. separation. 0159. In particular, the invention consists of a process for 0.174. The bottom of the column (comprising the alkox producing at least one alkoxyhydroxybenzaldehyde selected yphenolate) is preferably directed to the feed of the conden from vanillin (4-hydroxy-3-methoxybenzaldehyde), ethyl sation reactor So as to cause the alkoxyphenol (alkoxypheno Vanillin (3-ethoxy-4-hydroxybenzaldehyde), and any mix late) and the glyoxylic acid to react by condensation. ture thereof, from pyrocatechol. Oxidation of the Mandelic Compounds to Give 0160 According to one preferred variant, step (i) is carried Alkoxyhydroxybenzaldehyde out in a three-phase medium as described in the invention, including all the variants and embodiments described without 0.175. The oxidation step allows the conversion of the any limitation. mandelic compounds into the desired alkoxyhydroxybenzal 0161 According to one preferred embodiment, step (iii) dehydes. The para-mandelic compound corresponds more of separation of the dialkoxybenzene from the alkoxyphenol particularly to the abovementioned formula (IV). In particu US 2015/O 183702 A1 Jul. 2, 2015

lar, para-Vanillin (called here Vanillin) can be produced in 0182. At the end of the oxidation reaction, the precursor of Vanillate form by oxidation of the corresponding para-man the alkoxyhydroxybenzaldehyde (vanillin and/or ethylvanil delic acid. lin), i.e. with a hydroxyl group in Salified (ionic) form, and 0176 The alkoxyhydroxybenzaldehyde is obtained by various impurities, including tars, are obtained. oxidation of the corresponding mandelic compound, prefer 0183 In a subsequent step, the acidification of the alkoxy ably in an oxidizing atmosphere. Such as O or air. hydroxybenzaldehyde (vanillin and/or ethylvanillin) in the 0177 According to one variant, the reaction medium is an reaction medium is carried out using a strong acid, for alkaline aqueous medium, preferably an inorganic base and example sulfuric acid. It is then necessary to recover the noble more preferably sodium or potassium hydroxide, so as to product, namely the alkoxyhydroxybenzaldehyde (vanillin form the corresponding phenate, and to capture the released and/or ethylvanillin), in the presence of tars according to a process which is both friendly to the integrity of the products CO, in carbonate form. to be separated while at the same time being economical, and 0.178 The reaction may be carried out continuously or easy to carry out in industrial devices, quite particularly in batchwise, for example in a medium strongly diluted in water. those which operate continuously. To separate the alkoxyhy 0179 The reaction can be catalyzed. A catalyst of this droxybenzaldehyde (vanillin and/or ethylvanillin) from the oxidation reaction may be selected from catalysts comprising crude reaction mixture, a known method consists in carrying at least one metal element selected from the group formed by out the extraction thereof using an organic solvent. copper, nickel, cobalt, iron, manganese, and any mixture 0.184 Advantageously, the process comprises: thereof. By way of examples of inorganic or organic copper compounds, mention may in particular be made, as copper 0185 the separation of the alkoxyhydroxybenzalde compounds, of cuprous and cupric bromide; cuprous iodide; hyde from the reaction mixture by extraction with an cuprous and cupric chloride; basic cupric carbonate; cuprous organic solvent; and and cupric nitrate; cuprous and cupric Sulfate; cuprous Sulfite: 0186 the recovery and the recycling of the organic sol cuprous and cupric oxide; cupric hydroxide; cuprous and vent used for the extraction. cupric acetate; and cupric trifluoromethyl sulfonate. As spe 0187. Recycling Loop 2 cific examples of nickel derivatives, mention may be made of 0188 Recycling loop 2 covers the conversion of the nickel(II) halides, such as nickel(II) chloride, bromide or alkoxybenzaldehyde hydroxylate (vanillate and/or ethyl iodide; nickel(II) sulfate; nickel(II) carbonate; the salts of vanillate) obtained after the oxidation reaction to give the organic acids comprising from 1 to 18 carbonatoms, such as, corresponding alkoxyhydroxybenzaldehyde, and the recov in particular, acetate or propionate, nickel(II) complexes, ery and the recycling of the solvent used for the extraction of such as nickel(II) acetylacetonate, nickel(II) dichlorobis the alkoxyhydroxybenzaldehyde (vanillin and/or ethylvanil (triphenylphosphine) or nickel(II) dibromobis(bipyridine); lin) from the mixture resulting from the oxidation reaction. and nickel(0) complexes, such as nickel(0) bis(cycloocta-1, The invention covers in particular the production of vanillin 5-diene) or nickel(0) bisdiphenylphosphinoethane. As and/or of ethylvanillin. examples of cobalt-based compounds, mention may in par 0189 The reaction medium resulting from the oxidation is ticular be made of cobalt(II) and (III) halides, such as cobalt acidified with an acidic medium, preferably containing an (II) chloride, bromide or iodide or cobalt(III) chloride, bro inorganic acid, and for example Sulfuric acid, or hydrochloric mide or iodide: cobalt(II) and cobalt(III) sulfate; cobalt(II) acid, so as to convert the alkoxyhydroxybenzaldehyde Salt carbonate, basic cobalt(II) carbonate; cobalt(II) orthophos into alkoxyhydroxybenzaldehyde. phate; cobalt(II) nitrate; cobalt(II) and cobalt(III) oxide: 0190. According to one preferred embodiment, the cobalt(II) and cobalt(III) hydroxide; the salts of organic acids alkoxyhydroxybenzaldehyde contained in the aqueous phase comprising from 1 to 18 carbon atoms, such as, in particular, is extracted with an organic solvent which solubilizes the cobalt(II) and cobalt(III) acetate or cobalt(II) propionate: alkoxyhydroxybenzaldehyde contained in the aqueous phase. cobalt(II) complexes, such as hexaminecobalt(II) or (III) Use is made of an organic solvent which is inert with respect chloride, hexaminecobalt(II) or (III) sulfate, pentaminecobalt to the alkoxyhydroxybenzaldehyde. As solvents which can be (III) chloride or triethylenediaminecobalt(III) chloride. Use used, mention may in particular be made of halogenated or may also be made of iron-based catalytic systems, generally nonhalogenated aliphatic, cycloaliphatic or aromatic hydro in the form of oxides, of hydroxides or of salts, such as carbons; alcohols; ethers; ketones and nitriles. As aliphatic, iron(II) and iron(III) chloride, bromide, iodide or fluoride: cycloaliphatic or aromatic hydrocarbons, mention is more iron(II) and iron(III) sulfate; iron(II) and iron(III) nitrate; or particularly made of heptane, cyclohexane, methylcyclohex iron(II) and iron(III) oxide. The oxidation reaction can be ane, benzene and toluene; as halogenated aliphatic, catalyzed, for example, by a catalytic system comprising two cycloaliphatic or aromatic hydrocarbons, mention is more metal elements selected from the group formed by copper, particularly made of dichloromethane, trichloromethane, nickel, cobalt, iron, manganese, and any mixture thereof. The dichloroethane, chlorobenzene and dichlorobenzenes; as present invention covers in particular the reactions described alcohols, mention is more particularly made of methanol, according to patent application WO 08/148760. ethanol, propanol, isopropanol and butanol; as ethers, men 0180 Firstly, the mandelate compound reacts with the tion is more particularly made of diethyl ether, diisopropyl base (preferably sodium hydroxide) so as to salify the phenate ether and methyl (tert-butyl) ether; as ketones, mention is function of the mandelate compound. Then, the oxidation in more particularly made of acetone, methyl ethyl ketone, an oxidizing medium (preferably in air) produces vanillate methyl isobutyl ketone and diisobutyl ketone; and as nitriles, and CO (trapped in carbonate form). mention is more particularly made of acetonitrile. A mixture 0181. The oxidation of the para-mandelic compound to of said solvents may be used. give para-Vanillin is virtually complete, with very good selec 0191 The extraction operation is carried out at a tempera tivity. ture which depends on the nature of the solvent. US 2015/O 183702 A1 Jul. 2, 2015

0.192 This extraction step can be carried out at the same Hydroxyphenol O-alkylation time as the acidification. However, it is preferable for the reaction mixture and the organic solvent to be mixed together, Examples 1 to 4 (Hydroquinone “HQ') and then for the acid to be added. 0205 The following are charged batchwise, at 80°C., to a 0193 In order to isolate the alkoxyhydroxybenzaldehyde 150-liter 316L stainless steel reactor equipped with a jacket, (vanillin and/or ethylvanillin) from the extraction solvent, a with a mechanical stirrer, with a reflux condenser system and separation step can be carried out by recrystallization, but a with an inert gas (nitrogen) inlet: distillation of said mixture is preferably carried out, making it 0206. 21.9 kg (0.20 kmol) of crystalline hydroquinone possible to obtain, for example at the top of the distillation, the extraction solvent (if it is the most volatile compound of (HQ) the mixture) and, for example at the bottom of the distillation, 0207 x kg of demineralized water (cf. table below) a "crude alkoxyhydroxybenzaldehyde' ('crude' Vanillin 0208 2.6 kg (0.02 kmol) of an aqueous solution of and/or ethylvanillin), namely a mixture comprising essen sodium hydroxide at 30% by weight tially the alkoxyhydroxybenzaldehyde, combined with heavy 0209 y kg of methyl isobutyl ketone (MIBK) (cf. table impurities called “tars” and with small amounts of light impu below). rities. Reference is made, for this step in particular, to the The following are simultaneously injected into the reactor process described in patent application WO 2010/007161. containing the above aqueous solution, over the course of 45 0194 The organic solvent used is advantageously minutes under 10 bar at a temperature of 120° C.: recycled. It can be reintroduced into the process in order to 0210 28.3 kg (0.21 kmol) of an aqueous solution of extract the alkoxyhydroxybenzaldehyde from the aqueous sodium hydroxide at 30% by weight phase during the acidification, and/or used to recover the 0211 11.1 kg (0.22 kmol) of methyl chloride. alkoxyhydroxybenzaldehyde from the washing water. 0212. After reaction for 1.5 hours, the reaction medium is 0.195 Optionally, the alkoxyhydroxybenzaldehyde can be cooled to 30° C. and transferred to the “neutralization' sec treated in order to condition it in solid form. Preferably, the tion. A sample of this reaction medium is taken in order to alkoxyhydroxybenzaldehyde is purified, preferably by distil assay, by liquid chromatography, the compounds present lation, followed by crystallization (using one or more sol (p-methoxyphenol PMP and p-dimethoxybenzene PDMB, vents or by the flaking technique), for example according to and HQ) in the mixture and to determine the reaction perfor the following steps: mance levels. 0196) dissolution of the alkoxyhydroxybenzaldehyde in a water-alcohol mixture (for example methanol or Examples 1 2 3 4 ethanol); Water (x kg) 43.8 30.7 12.1 O 0.197 vacuum crystallization; MIBK (ykg) 12.7 19.1 28.7 39.0 MIBK/HQ (ml/mol) 8O 120 18O 245 0198 batchwise pulling dry; DC (HQ) 85% 87% 89% 89% 0199 drying of the alkoxyhydroxybenzaldehyde at a RY(PMP)/HQ 65% 70% 71.9% 71.9% RY(PDMB)/HQ 20% 18% 16% 16% temperature of 25°C. at a temperature below the melting R = dialkoxybenzenef O.34 O.29 O.25 O.25 point of the alkoxyhydroxybenzaldehyde, preferably alkoxyphenol (ww) under an inert gas (typically nitrogen). 0200. Several crystallization variants can be envisioned: for example batchwise crystallization, for example by cool Observation: An aqueous solution of hydroquinone can be ing, or continuous crystallization, for example under vacuum. prepared beforehand. 0213. These examples illustrate the effect of the amount of The resulting product can be optionally ground so as to obtain organic solvent on the dialkoxybenzenefalkoxyphenol ratio finer grains. and in particular on the p-dimethoxybenzene/p-methoxyphe nol ratio. Above a certain amount of organic solvent, there is Examples no effect of the amount of organic solvent on the dialkoxy benzene/alkoxyphenol ratio. On the other hand, below a cer 0201 In the examples, the degree of conversion, the yield tain amount of organic solvent, the invention illustrates the and the selectivity obtained are defined. effect on the dialkoxybenzene/alkoxyphenol ratio. This is 0202 The degree of conversion (DC) corresponds to the Surprising for those skilled in the art who were not expecting ratio between the number of moles of reagent (hydroxyphe such an effect. nol, for example) converted and the number of moles of 0214 Thus, it is possible to adjust the synthesis preferen reagent (hydroxyphenol, for example) used. tially toward one or other of the compounds according to the market demands, i.e. to be able to form to a greater or lesser 0203 The real yield (RY) is expressed by the ratio extent the compound of the dialkoxybenzene type compared between the number of moles of product formed (alkoxyphe with the alkoxyphenol, and vice versa, by using the amount of nol, for example) and the number of moles of reagent used organic solvent. Thus, the invention relates to a process for (hydroxyphenol, for example). producing at least one alkoxyphenol from at least one hydrox 0204 The selectivity or the yield with respect to the con yphenol which makes it possible to modulate or adjust the verted product (YC) is expressed by the ratio between the production of the dialkoxybenzene/alkoxyphenol ratio. Fur number of moles of product formed (alkoxyphenol, for thermore, this effect is observed on an industrial process for example) and the number of moles of reagent converted (hy which the conversion of the starting hydroxyphenol is maxi droxyphenol, for example). mized. US 2015/O 183702 A1 Jul. 2, 2015

Hydroxyphenol O-alkylation Condensation 0227. The following are continuously charged to a first Examples 5 to 7 (Pyrocatechol “PC”) 5-liter 316L stainless steel reactor equipped with a jacket, 0215. The following are charged batchwise, at 80°C., to a with a mechanical stirrer, with a pH electrode, with a reflux 150-liter 316L stainless steel reactor equipped with a jacket, condenser system and with an inert gas inlet: with a mechanical stirrer, with a reflux condenser system and 0228) 64.8 kg/h of demineralized water with an inert gas (nitrogen) inlet: 0229 9.3 kg/h (116 mol/h) of an aqueous solution of sodium hydroxide at 50% by weight 0216. 21.2 kg (0.19 kmol) of crystalline pyrocatechol 0230 10.1 kg/h (81.5 mol/h) of guaiacol (new and (PC) recycled from which all or part of the veratrole has been 0217 30.7 kg of demineralized water removed). 0218 2.5 kg (0.019 kmol) of an aqueous solution of 0231. This reaction mixture is maintained at a temperature sodium hydroxide at 30% by weight of 35°C. This preparation is then fed into the first reactor of 0219 x kg of methyl isobutyl ketone (MIBK) (cf. table a system of 3 reactors in cascade, with an aqueous solution of below). glyoxylic acid at 50% by weight (6.04 kg/h, i.e. 40.8 mol/h). 0220. The following are simultaneously injected into the 0232. The 3 perfectly stirred reactors are made of 316L reactor containing the above aqueous Solution, over the stainless steel and each have a volume of 801; they operate at course of 45 minutes under 10 barata temperature of 120°C.: 35o C. 0233. The overall residence time is 2 hours. 0221 21.8 kg (0.164 kmol) of an aqueous solution of 0234. At the outlet of the final reactor, a sample of this sodium hydroxide at 30% by weight reaction medium is taken and the compounds present in the 0222 8.9 kg (0.176 kmol) of methyl chloride. mixture are assayed by liquid chromatography. 0223. After reaction for 1.5 hours, the reaction medium is 0235. The results obtained are as follows: cooled to 30° C. and transferred to the “neutralization' sec 0236 conversion of guaiacol (GA): DC-47% tion. A sample of this reaction medium is taken in order to 0237 4-hydroxy-3-methoxymandelic acid (PMA): assay, by liquid chromatography, the compounds present YC(PMA)/GA=86% (guaiacol GA and veratrole VE and residual PC) in the mix 0238 2-hydroxy-3-dimethoxymandelic acid: ture and to determine the reaction performance levels. YC(OMA)/GA=5% 0239 2-hydroxy-3-methoxy-1,5-dimandelic acid: YC(DMA)/GA=9% Examples 5 6 7 0240. The reaction medium is sent to recycling loop 1 in MIBK (x kg) 12.3 18.5 27.8 order to separate the excess guaiacol from the mandelic com MIBK/PC (ml/mol) 8O 120 18O pounds. DC (PC) 79% 79% 80% RY(GA)/PC 72.1% 72.4% 74.5% 0241. Oxidation RY(VE)/PC 7.3% 6.6% 5.4% 0242. The 316L stainless steel oxidation reactor equipped R = dimethylated O.11 O.10 O.08 with a self-suction stirrer of cavitation type (“cavitator') or of monomethylated (wiw) Rushton type and with a jacket for efficient cooling is con tinuously fed with: Observation: An aqueous solution of pyrocatechol can be 0243 the mixture of the co-catalysts and of the aqueous prepared beforehand. Solution of mandelic compounds from loop 1, i.e.: 0244 77 kg/h of reaction medium resulting from the 0224. These examples illustrate the effect of the amount of condensation reaction, in which the excess guaiacol is organic solvent on the dialkoxybenzenefalkoxyphenol ratio removed (then recycled) in recycling loop 1. This and in particular on the Veratrole? guaiacol ratio. mixture contains about 7.2 kg/h of 4-hydroxy-3- 0225. As for examples 1 to 4, above a certain amount of methoxymandelic acid, 0.5 kg/h of 2-hydroxy-3- organic solvent, there is no effect of the amount of organic methoxymandelic acid and 0.9 kg/h of 2-hydroxy-3- solvent on the dialkoxybenzene/alkoxyphenol ratio. On the methoxy-1,5-dimandelic acid. other hand, below a certain amount of organic solvent, the 0245 100 g/h of an aqueous solution of CoCl and of invention illustrates the effect on the dialkoxybenzene/alkox CuSO in an amount expressed as molar percentage of yphenol ratio. This is surprising for those skilled in the art metal relative to the molar sum of the mandelic acids: who were not expecting Such an effect. 0.04% each; 0226. Thus, it is possible to adjust the synthesis preferen 0246 the appropriate amount of an aqueous Solution of tially toward one or other of the compounds according to the sodium hydroxide at 50% by weight corresponding at market demands, i.e. to be able to form to a greater or lesser least to the amount required by the stoichiometry of the extent the compound of the dialkoxybenzene type compared oxidation reaction (to be discussed together); with the alkoxyphenol, and vice versa, by using the amount of 0247 the amount of oxygen at atmospheric pressure organic solvent. Thus, the invention relates to a process for sufficient to have a virtually complete conversion of the producing at least one alkoxyphenol from at least one hydrox mandelic acids. The oxidizing agent may be oxygen at yphenol which makes it possible to modulate or adjust the atmospheric pressure or pressurized air. production of the dialkoxybenzene/alkoxyphenol ratio. Fur 0248. This reaction is carried out at 80°C. At the outlet of thermore, this effect is observed on an industrial process for the reactor, a sample of this reaction medium is taken and the which the conversion of the starting hydroxyphenol is maxi compounds present in the mixture are assayed by liquid chro mized. matography. US 2015/O 183702 A1 Jul. 2, 2015

0249. The results obtained are as follows: 6. The process as claimed in claim 2, wherein the process 0250 conversion of 4-hydroxy-3-methoxymandelic comprises: acid: DC-99.5% separating the alkoxyhydroxybenzaldehyde from the reac 0251 Yield of vanillin VA: tion mixture by extraction with an organic solvent; and recovering and recycling the organic solvent used for the extraction. 0252. The reaction medium is sent to the loop for extrac 7. The process as claimed in claim 1, wherein obtaining the tion of the Sodium Vanillate from the aqueous phase (termed alkoxyphenol comprises the following steps: recycling loop 2). O-alkylating at least one hydroxyphenol to give alkox yphenol in a basic multiphase medium comprising an 1. A process for producing alkoxyphenol, the process com organic phase and an aqueous phase; prising O-alkylating at least one hydroxyphenol to give at acidifying the resulting reaction medium; least one alkoxyphenol, wherein said O-alkylating comprises separating the organic phase containing the alkoxyphenol using an O-alkylating agent, an aqueous solvent comprising a compound from the aqueous phase containing the Bröensted base, and an organic solvent, with a base/O-alky Bröensted base and recovering the alkoxyphenol com lating agent ratio of between 0.5 and 1.5 in moles of base per pound. mole of O-alkylating agent, an O-alkylating agent/hydrox 8. The process as claimed in claim 1, wherein the process yphenol ratio of between 0.5 and 2 mol of O-alkylating agent consists of producing guaiacol and/or of guaethol from pyro per mole of hydroxyphenol, and an organic solvent/hydrox catechol or producing para-methoxyphenol and/or para yphenol ratio of less than 280 ml of organic solvent per mole ethoxyphenol from hydroquinone, by O-methylation and/or of hydroxyphenol. O-ethylation of one of the hydroxyl groups of the pyrocat 2. A process for producing alkoxyhydroxybenzaldehyde, echol or hydroquinone. the process comprising O-alkylating at least one hydroxyphe 9. The process as claimed in claim 1, wherein the O alky nol to give at least one alkoxyphenol as claimed in claim 1, lating is carried out in a basic multiphase medium with an and introducing an aldehyde function on the alkoxyphenolso organic solvent/water ratio, of less than 1.5 by weight. as to obtain the corresponding alkoxyhydroxybenzaldehyde. 10. A process for producing at least one alkoxyhydroxy 3. The process as claimed in claim 2, wherein the hydrox benzaldehyde compound, said process comprising: yphenol is pyrocatechol, wherein the O-alkylating is O-me (i)—synthesizing at least one alkoxyphenol from at least thylation and/or O-ethylation, wherein the alkoxyphenol is one hydroxyphenol in the presence of at least one selected from guaiacol and/or guaethol, and wherein the O-alkylating agent as claimed in claim 1: alkoxyhydroxybenzaldehyde is selected from vanillin and/or (ii)—recovering at least one alkoxyphenol and impurities, ethylvanillin. including a dialkylated compound of the dialkoxyben 4. The process as claimed in claim 2, wherein the process Zene type; comprises at least the following steps: (iii)—separating the dialkoxybenzene from the alkoxyphe condensing the alkoxyphenol compound with glyoxylic nol; acid so as to obtain the corresponding mandelic com (iv)—condensing the alkoxyphenol with glyoxylic acid pound; and obtaining the corresponding mandelic compound; separating the alkoxyphenol compound from the mandelic (V)—oxidizing the mandelic compound to give the corre compound, and optionally recycling the alkoxyphenol sponding alkoxyhydroxybenzaldehyde; and compound; (vi)—recovering the alkoxyhydroxybenzaldehyde option oxidizing the mandelic compound so as to obtain the ally in solid form. alkoxyhydroxybenzaldehyde; 11. The process as claimed in claim 10, wherein the at least separating the alkoxyhydroxybenzaldehyde by extraction one alkoxyhydroxybenzaldehyde is selected from vanillin with an organic solvent, then separating the alkoxyhy (4-hydroxy-3-methoxybenzaldehyde) and ethylvanillin droxybenzaldehyde from the organic solvent, and (3-ethoxy-4-hydroxybenzaldehyde) and wherein the hydrox optionally recycling the organic solvent; and yphenol is pyrocatechol. recovering the alkoxyhydroxybenzaldehyde, optionally in 12. The process as claimed in claim 1, wherein the organic solid form. solvent/hydroxyphenol ratio is between 10 and 250 ml of 5. The process as claimed in claim 4, wherein separating organic solvent per mole of hydroxyphenol. the alkoxyphenol compound from the mandelic compound 13. The process as claimed in claim 2, wherein introducing comprises the following steps: the aldehyde function occurs via a condensation reaction recovering a mixture comprising the mandelic compound between the alkoxyphenol and glyoxylic acid followed by formed in mandelate form and the unreacted alkoxyphe oxidation of the compound formed. nol in alkoxyphenolate form; 14. The process as claimed in claim3, wherein introducing neutralizing the alkoxyphenolate to give the alkoxyphenol, the aldehyde function occurs via a condensation reaction while maintaining the corresponding mandelate in Sali between the alkoxyphenol and glyoxylic acid followed by fied form; oxidation of the compound formed. separating the alkoxyphenol from the mandelate; 15. The process as claimed in claim 9, wherein the basic introducing the mandelate into an oxidation reactor, and multiphase medium has an organic solvent/water ratio of less recycling the alkoxyphenol, which has not reacted as a than 1.2 by weight. reagent, to the condensation reaction.