DE1162345B - Process for the preparation of ª ‡ -hydroxy and / or ª ‡ -oxoaldehydes or ketones - Google Patents

Description

Process for the preparation of α-hydroxy and / or α-oxoaldehydes or -ketones The production of α-hydroxycarbonyl compounds takes place in general by chlorination of the corresponding carbonyl compounds and careful saponification the a-chlorocarbonyl compounds obtained in this way by mild alkalis or alkali carbonates. The disadvantage of this process is that the chlorination with elemental Chlorine must carry out, with all of the chlorine partly as hydrogen chloride, partly is bound as alkali chloride than is lost in the form of by-products.

It is also already known to use carbonyl compounds with a-position To oxidize the methylene group with the help of selenium dioxide to α-dicarbonyl compounds.

Apart from the high price of this oxidizer, this shows known methods have the disadvantage that insoluble in the course of the oxidation reaction Selenium is produced, which only occurs after a complicated work-up and regeneration can be used again as an oxidizing agent. We are also involved in the oxidation reactions bound with selenium dioxide to the use of non-aqueous solvents.

It is known that the OH group is present in aromatic compounds to introduce copper (II) salts. In this way, for example, aniline can be used for o-aminophenol are oxidized. It is also known that one primary or secondary OH groups of aldehydes or ketones in the presence of copper (II) salts, such as copper acetate or copper sulfate, can oxidize to aldehyde or keto groups. Furthermore, one can d-xylose in the presence of copper (II) acetate and acetic acid as solvents Dehydrate a-dehydroxylose.

The present invention relates to a method of production of α-hydroxy and / or α-oxoaldehydes or ketones by oxidation, which thereby is characterized in that one saturated aldehydes or ketones with either aqueous Solutions of copper (II) or iron (III) salts, optionally with the addition of catalytic ones Quantities of precious metal salts, optionally in an acidic medium or with a moist and with these metal salts loaded carriers with a large surface, in the presence of Containing water vapor, optionally together with oxygen or free oxygen Gases, converts at about 30 to 2000 C, the resulting α-hydroxy and R or α-oxoaldehydes or ketones wins in a known manner and optionally - if the reaction carried out in the absence of oxygen or gases containing free oxygen - the separated copper (I) or iron (II) salts or the supported catalysts oxidized in a known manner and returned to the reaction.

In general, this reaction gives a mixture of the respective α-Hydroxycarbonyl compound and its corresponding dicarbonyl compound. Puts one such saturated aldehydes or ketones that are branched in the a-position Have a carbon skeleton, the α-hydroxycarbonyl compound initially formed is formed the dicarbonyl compound in more or less large amounts by rearrangement and Oxidation reactions.

You can, if desired, the yield of dicarbonyl compounds further increase if the α-hydroxycarbonyl compound obtained after the reaction again with copper (II) or

Iron (III) salts implemented. In this way you can achieve that in the end practically only α-dicarbonyl compounds are obtained. It is the other way around it is also possible under certain precautionary measures (e.g. with short dwell times) to prevent the formation of α-dicarbonyl compounds very largely and practically to obtain exclusively α-hydroxycarbonyl compounds.

The copper (II) or iron (III) salts are in the reaction in transferred to the 1- or 2-valued state. It is therefore convenient and a preferred one Measure of the process according to the invention, these metal salts by oxidizing agents to transfer them back to their effective higher valence level.

This oxidative regeneration is preferably carried out with such oxidizing agents, which even with repeated use no or practically no disturbing residues leave behind, which results in an inconvenient and time-consuming processing of the re- action solution unnecessary. Air and oxygen, in particular, are therefore used as oxidizing agents, but also ozone, hydrogen peroxide and their organic or inorganic derivatives, Acids of nitrogen, such as nitric acid or oxides of nitrogen, can be considered.

The reaction with simultaneous regeneration of the reduced copper or iron salt solutions can be carried out batchwise or continuously.

When working in batches, the procedure according to the invention is such that one the solution of a copper (II) or. Iron (III) salt in a first stage with the saturated aldehyde or ketone converts and in a second stage - after separation of the formed reaction products - the reduced metal salt solution on oxidative Paths regenerated and that regenerated in the original oxidation stage present metal salt again in the first stage again with saturated aldehydes or ketones converts. But it is also possible that the main reaction stage, in which the saturated aldehydes resp.

Ketones react with the copper (II) or iron (III) salt immediately containing an oxidizing agent, preferably oxygen or free oxygen Gases, supplied and so continuously the lower valence metal salt formed oxidatively regenerated.

It is also possible that the copper (lI) -bzw. Iron (III) saline solution on a carrier with a large surface, for example silica gel, carbon or aluminum oxide, precipitates and over these moist laden carriers simultaneously or one after the other a vaporous mixture of saturated aldehydes or ketones and water as well Conducts oxygen or gases containing free oxygen. With this procedure however, it is advisable not to keep the residence times and temperatures too low to keep so that the reaction to proceed to the stage of the α-hydroxycarbonyl compounds can and not undesired by-products, for example α-halocarbonyl compounds in the case of the use of copper or iron chlorides, arise to a considerable extent. In all of these forms of implementation it is necessary to do small from time to time Quantities of water, in the case of the use of metal halides also of hydrogen halide, add, which are lost to a small extent in the course of the reaction.

The process is carried out at temperatures between approximately 30 and 2000.degree. It is preferred to work at temperatures above the boiling point of the saturated aldehydes or ketones to be converted and are below 1500 C. Is working at temperatures above 1000 C, one generally works under pressure, the pressure to be used in each case is expediently higher than the boiling pressure of the aqueous solution at the reaction temperature.

From the aqueous, the a-hydroxy and / or a-dicarbonyl compounds solution containing these last-mentioned process products by per se gain known measures. In general, separation is achieved by simple means Distillation at normal pressure and preferably under reduced pressure. In individual Cases is also the azeotropic distillation of the organic reaction product with the water used as a solvent is possible. Substances that are not or only bad with Water vapor are volatile, can often be extracted with suitable Remove extractants from the aqueous reaction medium. Of course It is also possible to obtain chemical reactions to obtain the process products Kind of use. So you can optionally use the a-hydroxy or a-dicarbonyl compounds also separate with reagents characteristic for these groups of substances.

It is advisable to use the α-hydroxycarbonyl compounds or α-Dicarbonyl compounds relatively quickly after their formation from the aqueous To win reaction solution in order to continue reacting this often reactive Exclude substances in an undesirable manner.

To carry out the process of the invention, the salts are trivalent iron and the salts of divalent copper, especially their Halides, for example iron (III) chloride, iron (III) bromide, copper (II) chloride and copper (II) bromide. However, one can also use the salts of these metals with others Use acids, for example with sulfuric acid or organic acids. Man can also use salts of the same metal with different acid residues. In the end Excess free acid may also be present in the solution.

The copper (II) or iron (111) salt solution can also be catalytic Amounts of precious metal salts such as palladium, rhodium, platinum and iridium are added be.

Suitable saturated aldehydes or ketones with preferably at least 4 carbon atoms are, for example, butyraldehyde, isobutyraldehyde, methylethyl acetaldehyde, Diethylacetaldehyde, nonylaldehyde, methyl ethyl ketone, diethyl ketone, octanone-2 and Cyclohexanone.

Should the aqueous saline solution become noticeable after prolonged use Separate amounts of insoluble organic constituents, so you can get the solution in the German Auslegeschrift 1 146 045 and in the British patent 922694 can easily be regenerated by taking a branch stream this aqueous solution subjected to a thermal treatment, with which the oxidative regeneration of the lower valency salts present in this branch stream can couple. The regeneration of such a branch stream can be carried out continuously during the entire course of the reaction over time.

If undesired precipitations of the reduced occur during the reaction Valence level of the metal used, for example copper (I) chloride, so you can by the addition of solubilizers or by using a Excess of the metal in the higher valence level over that for implementation with the saturated aldehyde or ketone necessary stoichiometric amount often prevent the deposition of insoluble metal salts, as it has already done in the German Auslegeschrift 1 132910 has been described.

Example 1 1kg CuCl2 2H., O and 5 liters of water are mixed with 178 g of isobutyraldehyde Heated to reflux for 5 hours until the boiling point of the mixture was 950.degree has risen. Then 3 l of liquid are distilled on the descending condenser away. 5 g of trimeric isobutyraldehyde separate from the distillate in Crystals. Leave in a column by distilling the distillate again 89 g (= 41.6% of theory) of diacetyl are obtained as an azeotrope with water. in the At the bottom of this distillation there are 30 g of a-Hydroaxyisobutyraldehyde and Acetoin, which can be obtained through exhaustive etherification. That in aqueous suspension Any copper (I) chloride present can be converted back into copper (II) chloride by introducing air are oxidized. A little hydrochloric acid is then added until a clear solution is obtained receives.

Example 2 200 g of CuCl2 and 1 l of water are mixed with 40 g of methyl ethyl ketone Heated to reflux for 48 hours and the reaction mixture was distilled through a column. 35 g of an organic layer are obtained, which contains 12 g of diacetyl and 20 g of methyl ethyl ketone contains.

The copper contained in the solution is released by blowing in oxygen (I) chloride converted into copper (11) chloride and can be used again.

Example 3 In a reaction tube 2 m long and 5 cm in diameter there is a solution of 500 g CuCl ,! in 1 liter of water. The solution is through a jacket heater kept at 800 C. This solution results in 70 1 Air directed. At the same time, 20 g of isobutyraldehyde are in vapor form together with returned product initiated. Distill over the top of the gassing column 100 ccm of water-containing product per hour, from which 18 g of diacetyl are obtained can. The remainder of the product distilled off overhead, freed from diacetyl, which consists of water, hydroxyisobutyraldehyde, acetoin and a-chloroisobutyraldehyde, is in vapor form with fresh isobutyraldehyde in the bottom of the gassing column returned.

Example 4 In a 60 cm high column, 1.5 mol of iron (III) - chloride in 220g of water with 0.75 mol of isobutyraldehyde heated to reflux. At a Head temperature of 650 ° C., 40 g of distillate were removed, in which 10 g of diacetyl and 1 gram of acetoin was present. By gassing the reaction solution with oxygen the iron (II) salt formed during the reaction could be converted back into the trivalent one State.

Example 5 0.5 mol of Fe (SO4) was dissolved in 300 g of water and mixed with 0.5 moles of isobutyraldehyde on a 60 cm high column heated. At a head temperature 25 g of distillate of the following composition were taken from 650 C: 1.0 8 / o formaldehyde, 2.8% acetone, 3.6% α-oxyisobutyraldehyde, 28.0% diacetyl, 64.0% isobutyraldehyde.

This could be achieved by gassing the reaction solution with oxygen convert the iron (II) salt formed during the reaction back into the trivalent state.

Claims (2)

Claims: 1. Process for the production of a-hydroxy and / or α-Oxoaldehydes or ketones by oxidation, characterized in that saturated Aldehydes or ketones either with aqueous solutions of copper (11) or iron (III) salts, optionally with the addition of catalytic amounts of noble metal salts, optionally in an acidic medium or with moist carriers loaded with these metal salts with a large surface, in the presence of water vapor, optionally together with Oxygen or gases containing free oxygen, converts at about 30 to 2000 C, the α-hydroxy and / or α-oxoaldehydes or ketones formed in a known manner wins and optionally - if the reaction in the absence of oxygen or gases containing free oxygen is carried out - the separated copper (I) - or iron (II) salts or the supported catalysts are oxidized and in a known manner returns to the reaction. 2. The method according to claim 1, characterized in that the Reaction carried out at temperatures above 1000 C under pressures higher than are the boiling pressures of the aqueous solutions used. Documents considered: Tetrahedron letters, 2, 1958, P. 289; Journal of the Alnerican Chemical Society, 74, 1952, pp. 5162, 5163; 78 1956, pp. 3463 and 79, 1957, pp. 5279 to 5292; Chimie et Industrie, 83, 1960, no. 2, p. 236; Houben-Weyl, Methods of Organic Chemistry, 7/1, 1954, p. 190; Newer preparative methods of organic chemistry, 1944, pp. 4 to 9.