DE60006049T2 - Oxidation of alcohols mediated by nitroxyl derivatives - Google Patents

Description

Object of the present invention is a process for the oxidation of alcohols using a nitroxyl radical in the presence of a supported metal catalyst and a cooxidant.

The oxidation of alcohols is under organic chemical reactions are very common and is common in many processes well established in the industry. This applies in particular to the oxidation of primary alcohols to aldehydes or carboxylic acids to.

This oxidation can be catalytic Way to be carried out advantageously. Among known The catalytic process was the oxidation of alcohols with TEMPO and a cooxidant to a very attractive tool for the organic Synthesis (Semmelhack et al., J. Am. Chem. Soc., 105 (1983) 4492-4494). The authors used the stable organic nitroxyl radical 2,2,6,6-tetramethyl-piperidin-1-oxyl (TEMPO) as a mediator. The real oxidant is the nitrosonium ion, that can be synthesized from TEMPO using several methods.

soluble Fe (III) ions, for example, oxidize MeO-TEMPO to immonium oxide, which is a good activity for Oxidation of benzyl alcohol in a two-phase system (aqueous phase / acetonitrile or methylene chloride) shows. In this case, immonium oxide accelerates, which is a kind of ammonium salt, the reaction by Effect as an anion transport. The disadvantage of this procedure consists of the Fe (III) under stoichiometric conditions what was used given the pollution and cost of industrial Purposes is not feasible (Miyazawa, T. Endo., J. Molec. Catal., 31: 217-220 (1985).

The nitroxyl radical can also by copper (II) salt be oxidized to the oxoammonium salt, the alcohol to the corresponding Aldehydes, the hydroxylamine and a protonic acid oxidized. The hydroxylamine was again slightly oxidized by copper (II) salts to form a nitroxyl radical to give. But it was necessary to include the acid because it inhibits the catalytic oxidation system. Therefore copper (II) hydroxide or pyridine, again in stoichiometric Amounts, as an acid-trapping agent used (M.F. Semmelhack, C.R, Schmid, D.A, Cortes, C.S. Chou., J. Am. Chem. Soc., 106 (1984) 3374-3376; T. Miyazawa, T. Endo., J. Molec. Catal., 32 (1985) 357-360).

Sulfonic acid, p-toluenesulfonic acid or 1 (S) - (+) - camphor-10-sulfonic acid were to bring about the Oxoammonium salt used in methylene chloride as a solvent. consequently could be a big one Range of different alcohols to the corresponding aldehydes or Ketones are oxidized. However, alcohols with a β-oxygen will not oxidized by oxoammonium salts and with a δ-oxygen react slowly. The disadvantage of this method is that Use of an excess on nitroxyl radical and p-sulfonic acid (2 moles of nitroxyl radical were used per mole of alcohol) and leads to many steps for cleaning the products (Z. H. Ma, J. M. Bobbitt, J. Org. Chem, 56 No. 21 (1991) 6111-6114; J.A. Cella, J.A. Kelly, E. F. Kenehan., J. Org. Chem. 40 No. 62 (1975) 1860). This too The process is disadvantageous on an industrial scale.

Primary alcohols are quantitatively oxidized to aldehydes under two-phase conditions (methylene chloride-aqueous sodium hypochlorite) in the presence of catalytic amounts of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MeO-TEMPO). Simultaneous catalysis by bromide and buffering the pH at 8.6 with NaHCO ₃ are also required (PL Anelli, C. Biffi, F. Montanari, S. Quici, J. Org. Chem., 52 (1987) 2259-2562; T. Inokuchi, S. Matsumoto, T. Nishigama, S. Torii., J. Org. Chem., 55 (1990) 462-466).

Many authors have described a procedure for the oxidation of primary Hydroxyl functions in an aqueous Phase. The response is mediated by TEMPO, and hypobromite is used as the regenerating oxidant, which in turn by Hypohalite as an oxidant, preferably in the form of a salt such as Example lithium hypochlorite, sodium hypochlorite, potassium hypochlorite or calcium hypochlorite is regenerated (A.E.J. de Nooy, A.C. Besemer, H. Van Bekkum., Recl. Trav. Chim. Pays-Bas., 113 (1994) 165-166; A.E.J. de Nooy, A.C. Besemer, Tetrahedron, 51 No. 29 (1995) 8023-8032; P. S. Chang, J.F. Robyt, J. Carbohydr. Chem., 15 (7) (1996) 819-830.

More recently, 2,2,6,6-tetramethylpiperidine-1-oxyl water-mediated oxidation of primary hydroxyl groups of polysaccharide in the description of WO 95/07303, which discloses a method for Manufacture concerns completely carboxylated carbohydrates. In In this process, carbohydrates with a carbonyl content of oxidized at least 75% using the hypochlorite / bromide system. The Amount of hypochlorite solution used was 2-2.4 Moles per mole of monosaccharide unit. This clearly shows that that Process produces a lot of halogenated salts that have a certain Level of pollution (AOX waste).

The catalytic oxidation process of the above primary Hydroxyl groups have the following disadvantages:

In two-phase systems,

• - (i) leads the Oxidation of alcohol to aldehyde only.
• - (ii) the nitroxyl radical and the cooxidant became stoichiometric Amount used.
• - (iii) are many steps for cleaning of the products required.

In the aqueous phase,

• - (i) became a big one Co-oxidant excess (2 moles and more hypochlorite solution per mole of substrate) used.
• - (ii) the problems associated with this procedure sooner or later due to the loss of the oxidizing power of the N-oxoammonium salts of the simultaneously brought about Hydrogen peroxide and molecular chlorine (T. Endo, T. Miyazawa, S. Shiihashi, M. Okawara, J. Am. Chem. Soc., 106 (1984) 3877-3878) and an accumulation of halogenated salts and AOX.

The object of the present invention is another way of catalytic oxidation of To show alcohols using a nitroxyl radical that is not with those mentioned above Oxidation process associated disadvantages.

This goal is achieved through application one mentioned in claim 1 Procedure reached. Expectations 2 to 18 further apply to preferred embodiments of the invention.

wobei R¹, R², R³, R⁴, R⁵, R⁶ unabhängig voneinander (C₁-C₈)-Alkyl, (C₁-C₈)-Alkoxy, (C₆-C₁₈)-Aryl, (C₇-C₁₉)-Aralkyl, (C₆-C₁₈)-Aryl-(C₁-C₈)-Alkyl, (C₃-C₁₈)-Heteroaryl, (C₄-C₁₉)-Heteroaralkyl, (C₃-C₁₈)-Heteroaryl-(C₁-C₈)-Alkyl, (C₃-C₈)-Cycloalkyl, (C₃-C₈)-Cycloalkyl-(C₁-C₈)-Alkyl, (C₁-C₈)-Alkyl-(C₃-C₈)-Cycloalkyl darstellen oder R⁵ und R⁶ über eine (C₁-C₃)-Alkylkette, die durch ein oder mehrere R¹, N[(C₁-C₈)-Alkyl]₂, (C₁-C₈)-Amido, (C₁-C₈)-Alkyloxycarboxyl, (C₆-C₁₈)-Aryloxycarboxyl, Nitril, Hal, = O, Teil eines Polymers substituiert sein kann, verbunden sind, in Gegenwart eines Metall-Trägerkatalysators und eines Cooxidans, ist man fähig, Oxidationsprodukte zu gewinnen, die nicht von den aus dem Stand der Technik bekannten Nachteilen mit den Transformationen begleitet sind. Es können besonders der halogenierte Abfall (AOX) und die hyperstöchiometrische Verwendung kosteneffektiver und kaum entsorgbarer Cooxidanzien (Fe^3+/2+) weggelassen werden.By oxidation of alcohols by derivatives of the general formula (I)

where R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ independently of one another (C ₁ -C ₈ ) alkyl, (C ₁ -C ₈ ) alkoxy, (C ₆ -C ₁₈ ) aryl, (C ₇ -C ₁₉ ) aralkyl, (C ₆ -C ₁₈ ) aryl (C ₁ -C ₈ ) alkyl, (C ₃ -C ₁₈ ) heteroaryl, (C ₄ -C ₁₉ ) heteroaralkyl, (C ₃ -C ₁₈ ) heteroaryl- (C ₁ -C ₈ ) -alkyl, (C ₃ -C ₈ ) -cycloalkyl, (C ₃ -C ₈ ) -cycloalkyl- (C ₁ -C ₈ ) -alkyl, Represent (C ₁ -C ₈ ) alkyl- (C ₃ -C ₈ ) -cycloalkyl or R ⁵ and R ⁶ via a (C ₁ -C ₃ ) -alkyl chain which is represented by one or more R ¹ , N [(C ₁ -C ₈ ) alkyl] ₂ , (C ₁ -C ₈ ) amido, (C ₁ -C ₈ ) alkyloxycarboxyl, (C ₆ -C ₁₈ ) aryloxycarboxyl, nitrile, Hal, = O, part of a polymer substituted, linked, in the presence of a supported metal catalyst and a cooxidant, one is able to obtain oxidation products that are not accompanied by the disadvantages known from the prior art with the transformations. In particular, the halogenated waste (AOX) and the hyperstoichiometric use of cost-effective and hardly disposable cooxidants (Fe ^{3 + / 2 +} ) can be omitted.

A method is preferably used, wherein R ¹ to R ^{4 of} the formula (I) represent (C ₁ -C ₈ ) -alkyl and R ⁵ and R ⁶ via a (C ₁ -C ₃ ) -alkyl chain which is represented by one or several R ¹ , N [(C ₁ -C ₈ ) alkyl] ₂ , (C ₁ -C ₈ ) amido, (C ₈ -C ₁₈ ) aryloxy, (C ₁ -C ₈ ) alkyloxycarbonyl, (C ₆ -C ₁₈ ) aryloxycarbonyl, nitrile, Hal, = O, part of a polymer may be substituted (e.g. BT Miyazawa, T. Endo., J. Polym. Scien., 23 (1985) 2487-2494) ,

The most preferred R ¹ to R ⁴ are methyl and R ⁵ and R ⁶ are linked via a C ₃ alkyl chain.

The amount of derivatives used Formula (I) is not critical. You should look at the cost effectiveness of the process related quantity can be used. A method is preferred, wherein the derivative of the general formula (I) in the range of 0.01 mol% to 10 mole%, more preferably between 0.1 mole% and 4 mole% is used on the substrate.

The procedure can be done with primary and secondary Alcohols performed become. primary Alcohols are made according to their Reactivity much faster than the secondary oxidizes what the specialist in the discrimination between the two Groups in a way that helps primary alcoholic functions in the presence of secondary alcoholic groups in the same molecule are selectively oxidized can. The method according to the invention However, alcohol used preferably has a primary alcoholic function.

Primary alcoholic residues will be usually, depending of whether water is the reaction solvent or an organic medium is used to match the corresponding carboxylic acids or oxidized to the aldehyde (A.E. J. de Nony et al., Tetrahedron 1993, 51, 8023f). [What about synthesizing the aldehydes?] In a preferred embodiment according to the invention, the supported metal catalyst comprises metals in an oxidation state ± 0 or metal oxides. Silver is preferred as elemental metals, Chromium, palladium, bismuth, iron, vanadium, copper, cobalt, nickel, Molybdenum, Manganese, ruthenium or osmium or alloys thereof are used.

In addition, the metal oxides used can be MO _x with M = silver, chromium, palladium, bismuth, iron, vanadium, copper, cobalt, nickel, molybdenum, manganese, ruthenium or osmium or mixtures the same or mixed metal oxides thereof.

The carrier itself advantageously consists from micro or mesoporous Materials. The microporous Material can be derived from zeolite material, and the mesoporous material can be silicon dioxide, aluminum oxide, aluminophosphate, titanium oxide or Celite or carbon. The zeolite material used can Zeolites such as X, L, Y, mordenite, mesoporous materials such as from the M41-S family (MCM-41, MCM-48, MCM-50) or silicon dioxide, Aluminum oxide, amorphous silica-alumina, aluminophosphate, titanium oxide, Zirconium oxide and Celite represent.

The ratio of metal to carrier is in the range from 0.01% by weight to 60% by weight, preferably between 0.05 % By weight and 50% by weight and more preferably between 0.1% by weight and 30 Wt .-%.

The cooxidant used according to the invention must for oxidizing the corresponding hydroxylamine of the formula (I) for Nitrosonium ion must be strong enough in the presence of the catalyst.

On the other hand, it has to be mild enough not to destroy the alcohol to be oxidized. All oxidants with an E ₀ of> 0.3 and less than 2.5 are possible. The cooxidant is preferably selected from a group consisting of hydrogen peroxide, oxone, ozone, perborate, percarbonate, oxygen, N-methylmorpholine-4-oxide, peroxodisulfate or caroate.

The ratio of cooxidant to substrate is not critical, but is supposed to be economic and ecological establish as low as possible being held. Usually it is in the range of 1 to 20, preferably between 1-10, more preferably between 1-2 equivalents.

The method according to the invention is preferred in a solvent carried out. It is more preferred in water or an organic solvent, most preferably in acetone, acetonitrile, benzene, dioxane, diglyme, Tetrahydrofuran or water or mixtures thereof.

If water is part of the solvent represents, the pH in the range of 2 to 12, preferably between 8.5 and 10 are.

The temperature of the reaction can according to the applied molecules or reaction conditions selected become and is not critical. As a rule, it is in the range from -30 ° C to 100 ° C, preferred between -10 ° C to 50 ° C.

The catalyst can then be recovered and for subsequent Oxidation reactions can be reused.

The proposed mechanism works the catalytic system as explained in the following scheme:

The catalyst reoxidizes the hydroxylamine, that during oxidation of the alcohol to the corresponding nitroxyl radical or the corresponding nitrosonium ion is formed, which then becomes Is capable of oxidizing an alcohol function. To close the It is important to reoxidize the reduced metal (or cycle its equivalent) a primary To use Cooxidans.

The method according to the invention can be used for oxidation primary Very large alcohols Range can be used. Polyols are more preferred on the primary Hydroxyl groups than on the secondary and / or tertiary hydroxyl groups oxidized.

The method is particularly for Oxidation of water soluble Suitable polyols. The preferred substrate for the present oxidation is 1,2-propanediol (R '= Me and R '' = H).

The method according to the present invention can be primary for oxidation Alcohols can be used advantageously. Preferred alcohols are for example: n-butanol, cyclohexanol, cyclopentanol, 3-methylcyclohexanol, 2-methylcyclohexanol, 1-hexanol, 1-butanol, octanol, dodecanol, Octanol, (±) -2-norbornane-methanol, (1R) - (-) - nopol, piperonyl alcohol, cinnamyl alcohol, famesol, nerol, Geraniol. The more preferred substrates for the present oxidation reaction are: 1-butanol and 1-hexanol.

The method according to the present invention can be used for the regioselective oxidation of a wide range of different Carbohydrates are used if they have primary hydroxyl groups. Examples of carbohydrates include: methyl-α-D-glucopyranoside, Methyl-β-D-glucopyranoside, Octyl-β-D-glucopyranoside, Sucrose, dodecyl-D-glucopyranoside, α-D-glucopyranoside-1- (disodium phosphate), α-α-trehalose.

The preferred substrates of the present Oxidation are: methyl-α-D-glucopyranoside and sucrose and especially methyl-α-D-glucopyranoside.

• – Bei der Oxidation von primärem Alkohol oder primären Hydroxylgruppen, z. B. im Fall der Kohlenhydrate, werden eine extrem hohe Aktivität und Selektivität erreicht. Primäre Hydroxylgruppen von Methyl-α-D-glucopyranosid werden insbesondere in Gegenwart von sekundären regioselektiv oxidiert, Nebenreaktionen werden vermindert;
• – kleine Mengen Nitroxidradikal werden verwendet (0,1 – 4 Mol-% pro Mol Substrat);
• – das zuvor verwendete Hypochlorit/Bromid-System wurde durch ein umweltfreundliches katalytisches System ersetzt;
• – die erhaltenen Carbonsäuresalze weisen eine hohe Reinheit auf, die keiner weiteren Reinigung bedarf.

Compared to the usual methods, the method of the present invention has the following advantages:

• - In the oxidation of primary alcohol or primary hydroxyl groups, e.g. B. in the case of carbohydrates, extremely high activity and selectivity are achieved. Primary hydroxyl groups of methyl-α-D-glucopyranoside are oxidized in the presence of secondary regioselectively, side reactions are reduced;
• - small amounts of nitroxide radical are used (0.1 - 4 mol% per mole of substrate);
• - the previously used hypochlorite / bromide system has been replaced by an environmentally friendly catalytic system;
• - The carboxylic acid salts obtained have a high purity, which requires no further purification.

Linear or branched methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl or octyl, including all, come as (C ₁ -C ₈ ) -alkyl radicals of their possible isomers. The radical (C ₁ -C ₈ ) alkoxy corresponds to the radical (C ₁ -C ₈ ) alkyl, provided that it is bound to the ring via an oxygen atom.

It should be noted that (C ₃ -C ₈ ) cycloalkyl is cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl radicals.

Hal means fluorine, chlorine, bromine and Iodine.

(C ₆ -C ₁₈ ) aryl denotes aryl species with 6 to 18 carbon atoms, such as phenyl, naphthyl, phenanthryl.

(C ₇ -C ₁₉ ) aralkyl are aryl radicals which are connected to the corresponding molecule via a (C ₁ -C ₈ ) alkyl radical.

(C ₃ -C ₁₈ ) heteroaryl are aryl molecules in which at least one C atom is substituted by a hetero atom such as N, O, P, S. Possible molecules are pyrolyl, furyl, pyridyl, imidazolyl, quinolinyl, etc.

(C ₄ -C ₁₉ ) Heteroaralkyl are heteroaryl species which are linked to the corresponding molecule via a (C ₁ -C ₈ ) alkyl radical.

The (C ₁ -C ₃ ) alkyl chain represents groups such as methenyl, 1,2-ethenyl, 1,3-propenyl.

(C ₁ -C ₈₎ -Alkoxycarboxyl is bonded via a carboxyl function to the corresponding molecule (C ₁ -C ₈₎ alkoxy group. (C ₆ -C ₁₈₎ -Aryloxycarboxyl is bonded via a carboxyl function to the corresponding molecule (C ₆ -C ₁₈₎ aryl group. (C ₁ -C ₈ ) Amido represents a (C ₁ -C ₈ ) alkyl radical which is linked via an amido group to the molecule in question.

Examples:

The following examples illustrate the present invention further.

General description:

Experiments were carried out in a 250 ml glass batch reactor with thermostat equipped with a condenser, a thermometer and a magnetic stirrer. The pH was coupled with a pH meter (Titrolin-alpha) to a pH control unit and an automatic Burette (Metrohm 655, 20 ml flask) containing 1 M KOH was kept constant.

Oxidation process:

A defined amount of substrate (5 mmol) was dissolved in 100 ml of water. Then 30 mg (0.19 mmol) TEMPO and 10 mmol cooxidant added. The system was at 298 K and pH 9.5 equilibrated. The catalyst was added to the mixture immediately. The pH of the solution was changed while the reaction by automatic titration with 1 M KOH solution 9.5 kept constant. At the end of the reaction the pH was checked inflict of hydrochloric acid adjusted to pH 8 at pH = 8. Then the catalyst was through Filtration recovered, water and TEMPO were under vacuum removed at 313 K. The product mixture was placed under vacuum overnight Room temperature dried. The degree of oxidation of the substrate was determined after the silylation by means of gas chromatography.

For silylation z. B. 10 mg of the oxidized sugar is introduced into a gas chromatography tube and 600 ml of pyridine added. The solution was stirred until the mixture was completely solubilized. After that, 600 ml of hexamethyldisilazane and 150 ml of trifluoroacetic acid were introduced. The mixture was 30 min placed in an oven at 363 K. Then n-decane became the internal one Standard for quantitative analysis added. The products were made using of the GC SIEMENS with capillary column, Ultrachromapack, 25 m long and a flame ionization detector (FID) is analyzed.

Production of the catalysts:

- Metal - carried on Al ₂ O ₃ , AlPO ₄ and NaY

Ag-Na-Y, Ag-AlPO ₄ and Ag-Al ₂ O ₃ were produced by wet impregnation. Silver nitrate was added to a solution containing the carrier (10 g). The mixture was stirred for 15 h and then filtered, washed and dried at 373 K overnight. Then the catalyst was calcined in air at 773 K for 6 h. The composition of the catalysts was determined after dissolving the solids by inductively coupled plasma (ICP). The BET specific surface area and the average pore diameter were obtained from the adsorption isotherms of nitrogen at 77 K using the automatic volumeter from Micromeritics. The samples were first evacuated at 473 K for 16 h. The results are reported in Table 1.

Table 1: Characterizations of the catalysts

- Production of the silver carbonate on Celit

The carrier material is Celit Washing with methanol containing 10% concentrated hydrochloric acid and then cleaned with distilled water until the stock liquor was neutral. Then the material was dried at 393K.

Purified celite (10 g) was added to a mechanically stirred solution of silver nitrate (1.85 mmol, 0.31 g) in distilled water (100 ml). A solution of potassium hydrogen carbonate (0.15 g) in distilled water (100 ml) is slowly added to the stirred suspension. After the addition is complete, stirring is continued for a further 10 min. A yellow-green precipitate formed is collected by filtration and dried under reduced pressure on a rotary evaporator for several hours. The catalyst contains 0.17 mmol silver per gram of celite (0.088 mmol Ag ₂ CO ₃ per gram of reagent). The same procedure was repeated for a different percentage of silver (see Table 2).

Table 2:

- Other catalysts:

M-Na-Y or M-Al ₂ O ₃ catalysts with M = Cu, Co, V, Mn, Ni, Fe, Bi, Pd and / or Ru were produced by impregnation at room temperature. Bimetallic catalysts Ag-Cu and Ag-Co were also made. The composition of the catalysts was determined by inductively coupled plasma (ICP) after the solids had dissolved. The results are reported in Table 3.

Table 3:

- Physico-chemical characterization

The composition of the catalysts was determined after dissolving the solids by inductively coupled plasma (ICP). The BET specific surface area and the average pore diameter were obtained from the adsorption isotherms of nitrogen at 77 K using the automatic volumeter from Micromeritics. The samples were first evacuated at 473 K for 16 h. The X-ray diffraction study was carried out on the Siemens 5000 instrument equipped with a Cu lamp (λ _Cu = 1.54 A). The spectra from 2θ = 5 ° to 2θ = 100 ° were recorded.

The amount of acid locations was programmed using the temperature Desorption, TPD, determined by ammonia. At previously at 673 K below a stream of helium (above Night) calcined samples. The ammonia was adsorbed at 373 K for 15 min. The temperature was raised by a gradual increase of 10 ° C / min 1073 K increased. The desorbed ammonia was determined using HCl (0.025 M) using a special titrometer, coupled to a pH control unit and an automatic, the acid containing buret titrated. While temperature, pH and HCl consumption were recorded during the desorption.

Example 1:

Methyl α-D-glucopyranoside (0.97 g, 5th mmol) was dissolved in 100 ml of water. Then 30 mg (0.19 mmol) TEMPO and 2.28 g (10 mmol) ammonium peroxodisulfate added. The The system was equilibrated at 298 K and pH 9.5 with vigorous stirring (1000 rpm). Then 500 mg of catalyst were added to the mixture (zero time). The pH of the reaction was determined by means of automatic titration with 1 M KOH solution 9.5 kept constant.

For comparison, catalyst A and ammonium peroxodisulfate through catalyst I (10 mmol, 2.31 g) replaced. At the end of the reaction the pH was adjusted by adding hydrochloric acid set to 8.

Then the catalyst was recovered by filtration, water and TEMPO were removed under vacuum at 313K. The product mixture was dried overnight under vacuum at room temperature net. The degree of oxidation was determined after silylation using gas chromatography. The results are reported in Table 4.

Table 4: Oxidation of methyl-α-D-glucopyranoside over silver catalysts

pH = 9.5, 298 K, α-MDG / TEMPO = 26 (mol)

(): is the molar ratio between the substrate and silver

The selectivity of the catalyst for oxidation of methyl-α-D-glucopyranoside to methyl-α-D-glucopyranosiduronic acid very good. It was found that the oxidation was stoichiometric is when catalyst I is used in the absence of peroxodisulfate becomes. The silver oxide was reduced to metallic silver.

Using catalyst A in combination with peroxodisulfate with a molar ratio of α-MDG to Ag of 108, a very high selectivity for methyl-α-D-glucopyranosiduronic acid Get 97% with a 70% conversion. In this new process the silver acts as a catalyst.

Example 2:

Example 1 was repeated except that the ratio of peroxodisulfate to α-MDG was varied. The effect of the amount of peroxodisulfate on the catalytic properties of Ag-Al ₂ O ₃ is described in 1 shown. With a molar ratio of peroxodisulfate: α-MDG close to 2, a selectivity of 99% is obtained with a conversion of approx. 80 mol%.

Example 3:

Example 1 was repeated except that the percentage of silver was varied: 1, 2, 3 and 5% by weight. The use of a molar ratio of α-MDG: peroxodisulfate: TEMPO of 1: 2: 0.1. The result is in 2 shown.

The α-MDG oxidation is absent of silver very slowly with a conversion of approx. 7%. On the other hand the conversion increases with the percentages of silver and achieves a selectivity of 99% at 78% conversion for methyl-α-D-glucopyranosiduronic acid Plateau.

Example 4:

Example 1 was repeated except that Catalyst A was treated with carbonate using a carbonate-silver molar ratio of 0.5. Out 3 the conversion can be seen as a function of the reaction time for the parent catalyst A and for catalyst Ag-CO ₃ . The initial rate increases by a factor of 10 in the case of catalyst A-CO ₃ . This result can be interpreted by the fact that in the presence of carbonate the charge density on the silver decreases and more Lewis acid is formed. This hypothesis was based on the TPD of ammonia ( 4 ) verified.

Example 5:

α-MDG was in the presence of 500 mg of catalyst E (contains 5.8% by weight Silver) oxidized in the same way as in Example 1. The α-MDG conversion was 74% with a selectivity of 99 mol% for Methyl-α-D-glucopyranosiduronic acid.

Example 6:

α-MDG was in the presence of 500 mg of freshly made catalysts G and H, which contained different amounts of silver carbonate, oxidized. The reaction was carried out in the same way as in Example 1 described. The results are shown in Table 5.

Table 5

Example 7:

Various supported metal catalysts were used to oxidize methyl α-D-glucopyranoside using the following conditions:
Methyl α-D-glucopyranoside (0.97 g, 5 mmol) was dissolved in 100 ml of water. Then 30 mg of TEMPO and (2.28 g, 10 mmol) ammonium peroxodisulfate were added. The system was equilibrated at 298 K and pH 9.5 with vigorous stirring (1000 rpm). Thereafter, 500 mg of metal supported catalysts and / or mixed oxides were added to the mixture (zero time). The pH of the reaction was kept constant at 9.5 by means of automatic titration with 1 M KOH solution. At the end of the reaction, the mixture was neutralized to pH 8 by adding hydrochloric acid. Then the catalyst was recovered by filtration, water and TEMPO were removed under vacuum at 313K.

The product mixture was left overnight dried under vacuum at room temperature. The degree of oxidation was after silylation determined by gas chromatography. The results are shown in Table 6.

Table 6:

Example 8:

The catalyst W with 54 wt .-% silver was in two successive oxidation runs a fresh use of methyl-α-D-glucopyranoside, peroxodisulfate and TEMPO solution used. The reaction was carried out under the same conditions as described in Example 7. The results are out Table 7 can be seen.

Table 7:

Example 9:

1,2-propanediol (0.38 g, 5 mmol) was dissolved in 100 ml of water. Then 30 mg TEMPO and (2.28 g, 10 mmol) ammonium peroxodisulfate added. The system was equilibrated at 298 K and pH 9.5 with vigorous stirring (1000 rpm). Then 500 mg of catalyst D were added to the mixture (zero time). The pH of the reaction was kept constant at 9.5 by automatic titration with 1 M KOH solution.

At the end of the reaction the pH was by adding of hydrochloric acid set to 8. Then the catalyst was removed by filtration recovered, water and TEMPO were removed under vacuum at 313K. The product mixture was over Dried overnight under vacuum at room temperature. The degree of oxidation was determined by gas chromatography after silylation.

At the end of the reaction, the selectivity of the lactic acid is 75 mol% with 90% conversion of the 1,2-propanediol.

Example 10:

Example 9 was repeated except that Catalyst D was replaced with Ag carbonate on Celite, Catalyst H containing 1 mmol Ag ₂ CO ₃ / g Celite. At the end of the reaction, the selectivity of the lactic acid is 60 mol% with 75 conversion of the 1,2-propanediol.

Example 11:

Example 10 was repeated except that the ammonium peroxodisulfate was replaced by oxone (10 mmol, 3 g). At the end of the reaction is the selectivity of lactic acid 99 mol% with 8% conversion of the 1,2-propanediol.

Example 12:

Example 9 was repeated except that catalyst D by catalyst E, which contained 5.8% by weight of silver, was replaced. At the end of the reaction, the selectivity of the lactic acid is 64 mol% with 60% conversion of the 1,2-propanediol.

Example 13:

Example 12 was repeated except that the ammonium peroxodisulfate was replaced by oxone (10 mmol, 3 g). At the end of the reaction is the selectivity of lactic acid 55 mol% with 18% conversion of the 1,2-propanediol.

Claims (18)

Process for the oxidation of alcohols by derivatives of the general formula (I)

where R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ independently of one another (C ₁ -C ₈ ) alkyl, (C ₁ -C ₈ ) alkoxy, (C ₆ -C ₁₈ ) aryl, (C ₇ -C ₁₉ ) aralkyl, (C ₆ -C ₁₈ ) aryl (C ₁ -C ₈ ) alkyl, (C ₃ -C ₁₈ ) heteroaryl, (C4-C ₁₉ ) heteroaralkyl, ( C ₃ -C ₁₈ ) heteroaryl- (C ₁ -C ₈ ) -alkyl, (C ₃ -C ₈ ) -cycloalkyl, (C ₃ -C ₈ ) -cycloalkyl- (C ₁ -C ₈ ) -alkyl, ( C ₁ -C ₈ ) -Alkyl- (C ₃ -C ₈ ) -cycloalkyl or R ⁵ and R ⁶ via a (C ₁ -C ₃ ) -alkyl chain which is represented by one or more R ¹ , N [(C ₁ -C ₈ ) alkyl] ₂ , (C ₁ -C ₈ ) amido, (C ₁ -C ₈ ) alkyloxycarboxyl, (C ₆ -C ₁₈ ) aryloxycarboxyl, nitrile, Hal, = O, part of a polymer can be connected, in the presence of a supported metal catalyst and a cooxidant. A method according to claim 1, wherein R ¹ to R ^{4 represent} (C ₁ -C ₈ ) alkyl and R ⁵ and R ⁶ via a (C ₁ -C ₃ ) alkyl chain which is represented by one or more R ¹ , N [( C ₁ -C ₈ ) alkyl] ₂ , (C ₁ -C ₈ ) amido, (C ₁ -C ₈ ) alkoxycarboxyl, (C ₆ -C ₁₈ ) aryloxycarboxyl, nitrile, Hal, = O, part of a Polymers can be substituted, are bound. A method according to claim 1 and / or 2, wherein R ¹ to R ^{4 are} methyl, R ⁵ and R ⁶ are bonded via a C3 alkyl chain. Method according to one or more of claims 1 to 3, the derivative of the general formula (I) in the range of 0.01 Mol% to 10 mol%, preferably between 0.1 mol% and 4 mol% based is used on the substrate. Method according to one or more of claims 1 to 4, wherein the alcohol used has a primary alcohol function. The method of claim 5, wherein the alcohol is for corresponding carboxylic acid is oxidized. The method of claim 1, wherein the supported metal catalyst Metals in an oxidation state ± 0 or metal oxides. The method of claim 7, wherein the used Metals silver, chrome, palladium, bismuth, iron, vanadium, copper, Cobalt, nickel, molybdenum, Manganese, ruthenium or osmium or alloys thereof. A method according to claim 7, wherein the metal oxides used are MO _x with M = silver, chromium, palladium, bismuth, iron, vanadium, copper, cobalt, nickel, molybdenum, manganese, ruthenium or osmium or mixtures thereof or mixed metal oxides thereof. Method according to one or more of claims 1 to 9, the carrier used from micro or mesoporous Materials. The method of claim 10, wherein the microporous material can be derived from zeolite material and the mesoporous material Silicon dioxide, aluminum oxide, amorphous silica-alumina, aluminophosphate, Can be titanium oxide or celite or carbon. Method according to one or more of claims 1 to 11, the ratio from metal to beam is in the range of 0.05% by weight to 50% by weight. Method according to one or more of claims 1 to 12, the cooxidant being selected from the group consisting of hydrogen peroxide, Oxon, ozone, perborate, percarbonate, oxygen, N-methylmorpholine-4-oxide, Peroxodisulfate or Caroat. Method according to one or more of claims 1 to 13, the ratio from cooxidant to substrate in the range from 1 to 20, preferably between 1 and 10 equivalents lies. Method according to one or more of claims 1 to 14, the reaction in water or an organic solvent, preferably acetone, acetonitrile, benzene, dioxane, diethylene glycol dimethyl ether (diglyme), Tetrahydrofuran or mixtures thereof is carried out. The method of claim 15, wherein the pH is in the range from 2 to 12, preferably between 8.5 and 10 when water is on Part of the solvent is. Method according to one or more of claims 1 to 16, the temperature of the reaction in the range of -30 ° C to 100 ° C being preferred is between -10 ° C and 50 ° C. Method according to one or more of the preceding Expectations, the catalyst then being recovered and for subsequent Oxidation is used again.