Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
  • C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
  • C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
  • C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
  • C07C45/38—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups being a primary hydroxyl group

Definitions

• the present invention relates to a new level for the preparation of hydroxybenzaldehydes by oxidation of primary hydroxybenzyl alcccis using oxygen or oxygen-containing gases in alkaline aqueous media.
• very many methods, either chemical or catalytic, have been proposed for oxidizing a benzyl alcohol to the corresponding benzaldehyde.
• French patent application No. 77-13941 (2,350,328) teaches the use of a catalyst based on a noble metal from the platinum group associated with lead, silver, tellurium and / or tin and / or their compounds
• French patent application No. 75-09932 (2,305,420) describes a co-catalyst based on a bismuth derivative
• Japanese patent application No. 55-22615 reveals a process for the oxidation of piperonyl alcohol to piperonal in the presence of a catalyst containing a platinum group metal associated with an inorganic salt of a metal chosen from the following metals: lead, bismuth, silver and tin and finally, US Pat. No.
• 4,190,605 accelerates the catalytic oxidation by activating a palladium-based catalyst by prior reaction of the latter with a hydroxybenzyl alcohol. It should be noted that in all these processes the role of temperature is not negligible and can sometimes be decisive. It is also known to carry out the catalytic oxidation of a hydroxybenzyl alcohol in the presence of an organic solvent.
• the alkaline aqueous medium consists of an aqueous solution of an alkali hydroxide used in an amount such that the hydroxide / hydroxybenzyl alcohol molar ratio is between 2.25 and 10.
• the alkaline aqueous medium can be added of an organic solvent inert under the reaction conditions and miscible with water.
• the reaction medium can comprise an accelerator or a mixture of accelerators based on the following metals: copper, cobalt, iron and manganese.
• the accelerators which can be used are metal ions derived from oxides or from mineral or organic salts, anhydrous or hydrated, from copper, cobalt, iron and / or manganese, to various degrees of valency such as copper sulfate II, cobalt chloride II hexahydrate, iron chloride III, manganese sulfate II.
• the process according to the invention offers various advantages such as carrying out the oxidation in the homogeneous phase, the removal of a catalyst based on a noble metal from the platinum group, the possibility of carrying out the oxidation in the absence of catalyst of some nature that it is had according to the variant of the process in the presence of metal ions accelerators at various degrees of valence, inexpensive, previously mentioned and finally the possibility of working at temperatures which may not exceed 50 ° C.
• the amounts of accelerator (s) to be used in the variant of the process according to the invention can vary between wide limits. The accelerating effect is already noticeable with additions of 0.01 gram equivalent of the metal or of the metal compound per mole of hydroxybenzyl alcohol used. Usually, 0.01 to 0.5 gram-equivalent of the metal or of the metal compound is used per mole of hydroxybenzyl alcohol engaged.
• the process according to the invention is carried out in an alkaline aqueous medium, the alkaline agent advantageously being an alkali hydroxide such as sodium hydroxide or potassium hydroxide.
• the alkaline agent advantageously being an alkali hydroxide such as sodium hydroxide or potassium hydroxide.
• more than one mole of alkaline agent is used per mole of hydroxybenzyl alcohol used.
• the operation is carried out with an excess equal to or greater than 2.25 moles of alkaline agent per mole of alcohol engaged and the molar ratio of alkali agent to alcohol engaged is usually between 2.25 and 10.
• the concentration of hydroxybenzyl alcohol in the alkaline aqueous solution is generally chosen so as to preserve a solution throughout the oxidation reaction. Generally, a weight concentration of hydroxybenzyl alcohol, adopted between 5 and 40%, is adopted.
• the oxygen or the oxygen-containing gases are in intimate contact with the alkaline aqueous solution containing the starting hydroxybenzyl alcohol and optionally the accelerator (s).
• it usually works with good stirring and under an oxygen or oxygen-containing gas pressure higher than ambient pressure.
• this oxidation is carried out under a pressure between 2 and 10 bars.
• We can, if desired, follow the course of oxidation by the amount of oxygen absorbed, but more often this absorption stops by itself or slows down very strongly when the theoretical amount of oxygen necessary for form the sought aldehyde has been absorbed.
• the progress of the reaction is followed, if necessary, by physical analysis such as the nuclear magnetic resonance analysis of the proton, EMN, of a test sample previously treated.
• the process according to the invention is usually carried out at a temperature less than or equal to 50 ° C and advantageously at a temperature between 25 and 50 ° C.
• the primary hydroxybenzyl alcohols used as starting materials correspond to the general formula, I, in which m is equal to 1 or 2 n is equal to 1,2,3, ... (5-m)
• R identical or different, represent a hydrogen atom, a halogen atom, an alkyl, aryl, alkoxyl, hydroxyl, methylenedioxy, carboxyl group or a condensed nucleus.
• the substituents R which are particularly preferred are alkyl, alkoxyl, hydroxyl or methylenedioxy groups.
• the primary hydroxyethyl alcohols of general formula, I are known or can be obtained by known means such as the addition of one or more moles of formaldehyde to a substituted phenol of general formula, II:
• n is equal to 1,2,3,4 and R retains the meaning given above.
• Another advantage of the process according to the invention is that it can be carried out starting from crude, non-purified hydroxyethylbenzyl alcohols, containing inter alia various impurities resulting from their preparations, or even starting from mixtures of iscarous hydroxybenzyl alcohol (isomers of constitution).
• the hydroxybenzaldehydes formed are purified by known means such as entrainenent with water vapor, distillation, fractional crystallization, chromatography.
• the sought-after hydroxybenzaldehyde is isolated by acidification at pH less than or equal to 3.5 of the reaction medium which has been previously filtered, if necessary, to possibly remove some mechanical impurities, followed by separation of the 'hydroxyben ⁇ zaldehyde thus released by means known per se such as filtration, extraction, entrainanent with steam.
• the hydroxybenzaldehyde can then be purified by known means such as recrystallization, distillation, etc.
• Reaction times vary depending on many factors: nature of the starting alcohol, stirring speed, reaction temperature, pressure of oxygen or oxygen-containing gas, concentration of accelerator and alkaline agent, etc. .. and they can vary in a wide range, but they are generally between 1 hour and 48 hours.
• the hydroxybenzaldehydes obtained according to the process of the invention are important intermediates in organic synthesis and / or precious materials for obtaining aromas or perfumes.
• the combined organic extraction phases are then washed with water, dried over anhydrous magnesium sulphate, filtered and concentrated to dryness under vacuum at a temperature below 30 ° C.
• the yield, R is the number of moles of aldehyde formed on the number of moles of alcohol used, multiplied by one hundred.
• the conversion rate, T is the ratio of the number of moles of alcohol consumed over the number of moles of alcohol used, multiplied by one hundred.
• Selectivity, S is the ratio of the number of moles of aldehyde formed over the number of moles of alcohol consumed, multiplied by a hundred.
• the mixture is heated to 50 ° C. for 24 hours with stirring at 1000 revolutions per minute and under a pressure of 8 bars of oxygen a mixture of: - 0.63 mole (78.2 g) of parahydroxybenzyl alcohol,
• the metal salt to parahydroxybenzyl alcohol molar ratio is 0.0127.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Catalysts (AREA)

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• 1981
  • 1981-01-20 FR FR8100967A patent/FR2498180A1/fr active Granted
• 1982
  • 1982-01-14 US US06/414,243 patent/US4481374A/en not_active Expired - Fee Related
  • 1982-01-14 CA CA000394180A patent/CA1173049A/fr not_active Expired
  • 1982-01-14 JP JP57500275A patent/JPS6332343B2/ja not_active Expired
  • 1982-01-14 EP EP82400064A patent/EP0058100B1/fr not_active Expired
  • 1982-01-14 WO PCT/FR1982/000007 patent/WO1982002549A1/fr not_active Ceased
  • 1982-01-14 DE DE8282400064T patent/DE3261639D1/de not_active Expired

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