Process for preparing mandelic aromatic compounds and aromatic aldehyde compounds

Abstract

A process for preparing an aromatic compound or compounds where at least one mandelic group CHOHCOOH is described, comprising a reaction for condensation of at least one aromatic compound with glyoxylic acid or derivatives thereof, wherein said condensation reaction is carried out substantially in the absence of any acid or any base added to the reaction medium. The condensation reaction is followed by an oxidation reaction in order to obtain aromatic aldehyde.

Claims

1. A process for the preparation of one or more mandelic aromatic compounds carrying at least one mandelic CHOHCOOH group comprising: reacting at least one aromatic compound with glyoxylic acid or esters of glyoxylic acid under condensation conditions in the absence of any added acid or added base other than those constituted by reactants, an optional catalyst and an optional solvent, wherein the said aromatic compound is a substituted benzene substituted by one or more alkoxy groups, phenol or a substituted phenol according to formula (I): ##STR00004## wherein: R represents one or more identical or different substituents, x, the number of substituents on a ring, is an integer between 1 and 4, wherein R is selected from the group consisting of hydroxyl, linear or branched alkyl having from 1 to 6 carbon atoms, linear or branched alkoxy having from 1 to 6 carbon atoms and wherein a molar ratio of the said aromatic compound to glyoxylic acid or esters of glyoxylic acid varies from 0.9 to 1.1; and recovering condensation products directly after the condensation reaction of the at least one aromatic compound with glyoxylic acid or esters of glyoxylic acid without intervening steps.

2. The process of claim 1, wherein said aromatic compound is a substituted phenol wherein the position para with respect to the hydroxyl group of the substituted phenol according to formula (I) is unsubstituted.

3. The process of claim 1, wherein the substituted phenols are selected from the group consisting of o-cresol, m-cresol, 3-ethylphenol, 2-(tert-butyl)phenol, guaiacol, and guaethol.

4. The process of claim 1, wherein the glyoxylic acid is in the monohydrate form.

5. The process of claim 1, wherein the step of reacting is carried out in the presence of at least one catalyst.

6. The process of claim 5, wherein the catalyst is selected from transition metal complexes comprising oxygen-comprising ligands.

7. The process of claim 5, wherein the catalyst is selected from the group consisting of: iron(II) acetate, iron(III) acetate, copper(II) acetate, iron(II) acetylacetonate, iron(III) acetylacetonate, copper(II) acetylacetonate, and copper(III) acetylacetonate.

8. The process of claim 5, wherein the catalyst comprises a complex composed of a transition metal and at least one glyoxylate ligand.

9. The process of claim 1, wherein the optional solvent is selected from the group consisting of water, aromatic hydrocarbons, alcohols, and water-alcohol mixtures.

10. The process of claim 1, wherein the process consists of reacting the glyoxylic acid with guaiacol, with guaethol, or with guaiacol and guaethol.

11. A process for the preparation of one or more mandelic aromatic aldehydes comprising: reacting at least one aromatic compound with glyoxylic acid or esters of glyoxylic acid according to the process of claim 1 to prepare one or more mandelic aromatic compounds, and oxidizing the one or more mandelic aromatic compounds.

12. The process of claim 11, wherein the step of oxidizing is carried out without addition of alkaline agent.

13. The process of claim 11, wherein the step of oxidizing is carried out in the presence of water as solvent.

14. The process of claim 11, wherein the step of oxidizing is carried out in the presence of a catalyst selected from the group consisting of chromium, cobalt, copper, vanadium, manganese, iron, nickel and osmium derivatives.

15. The process of claim 11, wherein the one or more aromatic aldehydes comprise vanillin, ethylvanillin, or vanillin and ethylvanillin.

16. The process of claim 1, wherein recovering the condensation products involves separation of mandelic aromatic compounds obtained from the condensation reaction by crystallization.

17. The process of claim 1, wherein recovering the condensation products involves separation of mandelic aromatic compounds obtained from the condensation reaction by extraction with at least an organic solvent.

18. The process of claim 1, wherein the reactor contents consist essentially of the reactants, the optional catalyst, the optional solvent, and an optional inert atmosphere.

Description

EXAMPLES

Example 1

Preparation of Aromatic Compounds Carrying at Least One Mandelic Group by a Condensation Reaction of Glyoxylic Acid with an Aromatic Compound

(1) An amount of an aromatic compound is introduced into a 50 ml reactor provided with a temperature probe and with a mechanical stirrer and is heated to the temperature appearing in table 1. When the desired temperature is reached in the reactor, an amount of glyoxylic acid monohydrate in the solid form and a catalytic amount of Fe(acac).sub.3, that is to say an amount representing 2.5 mol % with respect to the limiting reactant, is introduced. In this example, considering that said aromatic compound and glyoxylic acid are employed according to an equimolar ratio, the amount of Fe(acac).sub.3 is such that it represents without distinction 2.5 mol % with respect to either of said two reactants. The reaction mixture is kept under magnetic stirring at the desired temperature for a period of time varying between 1 and 22 hours (cf table 1). At the end of the reaction, the products from the condensation reaction are assayed by high-performance liquid chromatography. The results obtained are collated in table 1.

(2) TABLE-US-00001 1,2,3- Aromatic Trimethoxy- Benzo- compound Phenol* Guaiacol Guaethol o-Cresol Veratrole benzene furan Molar 1 1 1 1 1 1 1 ratio Aromatic compound/ glyoxylic acid T ( C.) 45 45 45 45 45 45 80 Duration 20 3 5 1 22 22 20 (hour) Conversion 87 85 85 85 35 75 75 of the aromatic compound (%) Yield of 75 60 50 62 19 37 70 mandelic compound (%) *The condensation reaction carried out using phenol as aromatic compound was carried out in the presence of water as solvent according to a glyoxylic acid/water ratio by weight = 50/50.

(3) The conversion of the aromatic compound corresponds to the ratio of the number of moles of aromatic compound consumed to the number of moles of aromatic compound employed.

(4) The yield of mandelic compound corresponds to the ratio of the number of moles of mandelic compound formed to the number of moles of one or other of the reactants.

Example 2

(5) 1.5 mmol of guaiacol and 1.5 mmol of glyoxylic acid monohydrate are introduced into a 25 ml reactor equipped with a temperature probe and with a mechanical stirrer and heated at 50 C. on a water bath. No catalyst is added in this test. The reaction mixture is kept under magnetic stirring at 60 C. for 1 hour.

(6) At the end of the reaction, the products from the condensation reaction are assayed by high-performance liquid chromatography. The conversion of guaiacol is 52% and the yield of mandelic compound is 30%.

Example 3

(7) 1.5 mmol of guaiacol, 1.5 mmol of glyoxylic acid monohydrate and 1 mol % of a catalyst are introduced into a 25 ml reactor equipped with a temperature probe and with a mechanical stirrer and heated at 50 C. on a water bath. The reaction mixture is kept under magnetic stirring at the desired temperature for 1 hour.

(8) At the end of the reaction, the products from the condensation reaction are assayed by high-performance liquid chromatography. The results obtained are collated in the table below:

(9) TABLE-US-00002 Catalyst Fe(acac).sub.3 Fe(acac).sub.3 Cu(OAc).sub.2 Cu(OAc).sub.2 Temperature 50 C. 60 C. 50 C. 60 C. Conversion of 43 80 12 80 the aromatic compound (%) Yield of 35 56 11 26 mandelic compound (%)

Example 4

(10) Vanillylmandelic acid (1 mol/l) is introduced into an open, magnetically stirred, 8 ml vial containing a catalyst and a solvent. The concentration of catalyst is 1 mol %, with respect to the number of moles of vanillylmandelic acid. The reaction is carried out at 80 C. for 15 hours.

(11) The yields of vanillin obtained, as a function of the catalyst and of the solvent used, are collated in the table below:

(12) TABLE-US-00003 Catalyst Water Isopropanol V.sub.2O.sub.5 28 55 NH.sub.4VO.sub.3 20 68 VO(acac).sub.2 61 18 Cu(OAc).sub.2 5 86

Example 5

(13) Vanillylmandelic acid (0.1 mol/l) is introduced into a stirred reactor under O.sub.2 pressure containing a catalyst (NH.sub.4VO.sub.3) and a solvent (water). The concentration of catalyst is 2.5 mol %, with respect to the number of moles of vanillylmandelic acid. The reaction is carried out at 80 C. under 7 bar for 180 minutes.

(14) The degree of conversion of the vanillylmandelic acid is 100% and the yield of vanillin is 93%.