Definitions

• the invention relates to the selective oxidation of primary alcohols, using an oxidising agent in the presence of a catalytic amount of a di-tertiary-alkyl nitroxyl compound, especially 2,2,6,6-tetramethylpiperidin- 1 -oxyl (TEMPO) .
• TEMPO 2,2,6,6-tetramethylpiperidin- 1 -oxyl
• TEMPO cyclic and/or di-tert-alkyl nitroxyls
• Doxyl 4,4-dimethyloxazolidine-N-oxyl
• Proxy 2,2,5,5-tetramethylpyrrolidine-N-oxyl
• 4-hydroxy-TEMPO and derivatives thereof, especially 4-acetamido TEMPO, and those described in WO 95/07303 can be substituted for TEMPO.
• the catalytic amount of nitroxyl is preferably 0.1-10%, more preferably 0.2-3% by weight, based on the primary alcohol, or 0.1-10 mol% (0.2-3%) with respect to the primary alcohol.
• the peroxosulphate present in the process of the invention serves for regenerating TEMPO.
• the peroxosulphate may be a straight peroxomonosulphate, MHSO 5 , M 2 SO 5 or the persulphuric acid H 2 SO 5 , wherein M is an alkali metal or other metal (taking account of its valency in the formula), ammonium or substituted ammonium.
• M is an alkali metal or other metal (taking account of its valency in the formula), ammonium or substituted ammonium.
• the peroxosulphate is Oxone® (2KHSO 5 .KHSO 4 .K 2 SO 4 ), which is commercially available. It is not necessary and not recommended to use any halogen, as a co-oxidant.
• the amount of peroxosulphate is equivalent to the amount of primary hydroxyl groups to be oxidised. If complete oxidation of -CH 2 OH groups to carboxyl groups -COOH is desired, 2 - 2.4 moles of peroxosulphate per mol of primary hydroxyl groups is advantageously used.
• the process of the invention results in oxidation of primary alcohols initially to the corresponding aldehydes, and eventually to the corresponding carboxylic acids.
• the second oxidation step from aldehyde to carboxylic acid, proceeds at a faster rate than the first step, i.e. the oxidation from alcohol to aldehyde.
• the maximum fraction of aldehyde functions present will be below about 10 (based on the number of primary hydroxyls available for oxidation).
• the present process is especially favourable for the selective oxidation of primary hydroxyl groups in alcohols having a secondary alcohol function in addition to the primary alcohol, such as 1,6-octanediol, 1,9-octadecanediol, sugar alcohols, glycosides, and in particular carbohydrates having primary alcohol functions, especially polysaccharides having chain lengths of at least 5 anhydroglycose units, such as glucans (starch, cellulose), furano- fructans, galactans, (galacto)mannans, and the like.
• a particular group of compounds suitable for oxidation with the present process are hydroxyalkylated, especially hydroxyethylated carbohydrates such as hydroxyethyl starch or hydroxyethyl inulin. These derivatives result in an alternative way for producing formylmethyl and carboxymethyl carbohydrates.
• Potato starch (3.0 g, 18.5 mmol anhydroglucose units) was gelatinised in demi- water (200 ml) at 95°C with effective mechanical stirring.
• 4-Acetamido-TEMPO (61 mg, 0.29 mmol) was added and dissolved.
• the solution was cooled on ice and the temperature was maintained ⁇ 10°C throughout the reaction.
• the reaction was initiated by the addition of Oxone (11.38 g, 2 mol HSO 5 7mol primary alcohol), which was added under mechanical stirring in small portions throughout the oxidation to minimise unwanted side reactions.
• pH was raised to 8.2 and then kept constant by the addition of 0.5 M NaOH using a pH stat apparatus.
• Example 2 Methyl ⁇ -D-glucopyranoside (1.0 g, 5.1 mmol) and 4-acetamido-TEMPO (20 mg, 0.09 mmol) were dissolved in water (50 ml). The solution was cooled on ice and the temperature was maintained at ⁇ 10°C throughout the reaction. The reaction was initiated by the addition of Oxone (3.17 g, 2 mol HSO 5 7mol primary alcohol), which was added in small portions under mechanical stirring throughout the oxidation to minimise unwanted side reactions. After each addition of the acidic oxidant, pH was raised to 8.2 and then kept constant by the addition of 0.5 M NaOH using a pH stat apparatus.
• Oxone 3.17 g, 2 mol HSO 5 7mol primary alcohol
• Amylopectin (waxy starch maize) (3.0 g, 18.5 mmol anhydroglucose units) was gelatinised in demi-water (200 ml) at 95°C with effective mechanical stirring. 4-Acetamido-TEMPO (61 mg, 0.29 mmol) was added and dissolved. The reaction was initiated by the addition of Oxone (11.38 g, 2 mol HSO 5 7mol primary alcohol), which was added under mechanical stirring in small portions throughout the oxidation to minimise unwanted side reactions. The reaction procedure was identical to that in Example 1. The conversion of the primary hydroxyls to carboxyls was estimated by C NMR to be 58 mol%.

Landscapes

• Polysaccharides And Polysaccharide Derivatives (AREA)

Priority Applications (1)

Applications Claiming Priority (6)

Publications (1)

Family

ID=28045905

Family Applications (1)

Country Status (1)

• 2001
  • 2001-12-12 EP EP01270556A patent/EP1349876A1/de not_active Withdrawn

Non-Patent Citations (1)

Similar Documents

Legal Events