JPH0364491B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the general formula The present invention relates to a method for producing an unsaturated carbonyl compound represented by the formula (wherein R ¹ , R ² , R ³ and R ⁴ are hydrogen, an alkyl group, an alkenyl group or an aryl group). More specifically, the present invention provides a method for converting the general formula (In the formula, R ¹ , R ² , R ³ and R ⁴ are hydrogen, an alkyl group, an alkenyl group or an aryl group.) By dehydrogenating the unsaturated alcohol represented by the formula using oxygen gas, the above-mentioned general The present invention relates to a method for producing an unsaturated carbonyl compound represented by formula (). The unsaturated carbonyl compound represented by the general formula () is widely used as fragrances, pharmaceuticals, etc., or raw materials for their production.

Conventionally, in order to produce the unsaturated carbonyl compound represented by the above general formula () from the unsaturated alcohol represented by the above general formula (2), (a) a method of oxidizing with a reagent oxidizing agent such as manganese dioxide [new method] Experimental Chemistry Course 15 Maruzen (1976)]
(b) Oxygen oxidation method using a platinum catalyst [see New Experimental Chemistry Course 15 Maruzen (1976)], (c) Oxygen oxidation method using a complex catalyst such as tristriphenylphosphine ruthenium () dichloride (Ito, Matsumoto, Proceedings of the 43rd Spring Annual Meeting of the Chemical Society of Japan,
1L36, 1981) are known. However (a)
This method requires the use of oxidizing reagents in a stoichiometric manner and is difficult to adopt industrially due to problems such as treatment of the resulting reduction products. The method (b) has problems in selectivity, such as the production of carboxylic acids and the like as by-products. Method (c) has low catalytic activity, requires complicated preparation of the catalyst, and uses a phosphine complex that is unstable under oxidation conditions as a catalyst, making it difficult to reuse the catalyst.

As a result of studies to overcome the drawbacks of conventional methods, the present inventors discovered an industrial method for easily converting an unsaturated alcohol into the corresponding unsaturated carbonyl compound with good yield and completed the present invention.

Examples of the unsaturated alcohol represented by the general formula () that is a raw material of the present invention include allyl alcohol, crotyl alcohol, prenol, geraniol, nerol, farnesol, retinol,
Unsaturated primary alcohols such as 2-(β-ionylidene)ethanol and cinnamyl alcohol, and 3-
Hydroxy-1-butene, 3-hydroxy-1-
Examples include unsaturated secondary alcohols such as phenyl-1-butene, β-ionol, and carveol.

The method of the present invention requires dehydrogenation of the unsaturated alcohol represented by the general formula () using oxygen gas in the presence of a ruthenium dioxide () catalyst.

Examples of the oxygen gas used in the present invention include oxygen gas, a mixed gas of oxygen and an inert gas, and air.

As the ruthenium dioxide used in the present invention, commercially available anhydrous ruthenium dioxide (), hydrated ruthenium dioxide () or halogenated ruthenium,
Any ruthenium dioxide prepared from a ruthenium compound such as ruthenium tetroxide may be used, but it is preferable to use a form with as large a surface area as possible. In addition, for use in the reaction, the above-mentioned ruthenium dioxide () may be used in a homogeneous system, or it may be supported on a carrier such as silica gel, alumina, or activated carbon using any technique commonly used for the production of powder or heterogeneous catalysts. It may also be used as a heterogeneous system dispersed in a solution.

In carrying out the present invention, it is not necessary to use a solvent, but if it is desired to use a solvent, for example, a saturated hydrocarbon such as pentane, hexane, heptane, or a mixture thereof, dichloromethane, chloroform, tetrachloride, etc. Carbon, halogenated hydrocarbons such as dichloroethane, trichloroethane, 1,1,2,2,-tetrachloroethane, aromatic hydrocarbons such as benzene and toluene, carbonyl compounds such as acetone and methyl ethyl ketone, tetrahydrofuran, dioxane, 1,2- Examples include ethers such as dimethoxyethane, saturated alcohols such as methanol and ethanol, and esters such as ethyl acetate, propyl acetate, butyl acetate, and pentyl acetate.

Furthermore, in carrying out the present invention, it is preferable to add an antioxidant to the reaction system and to dilute the reaction system with a solvent in order to suppress side reactions. When using an antioxidant, 2,6-di-t-butyl-p
So-called hindered phenols such as -cresol, 2,4,6-tri-t-butylphenol, and 2,6-di-t-butylhydroquinone can be used. Further, the amount of antioxidant to be used is sufficient at a weight ratio of 1/100 or less to the reaction substrate.

In the present invention, the oxidation reaction proceeds under atmospheric pressure and at room temperature, but in terms of reaction efficiency, the reaction temperature is preferably in the range of 50 to 120°C.
Preferably, the reaction is carried out under a pressurized atmosphere of oxygen gas.

The feature of the present invention is that the unsaturated alcohol of the general formula () can be easily converted into the unsaturated alcohol of the general formula () in the presence of oxygen gas by using a ruthenium dioxide () catalyst.
In addition to converting into unsaturated carbonyl compounds, the stereochemistry between the raw material and the product is largely maintained during the reaction process, and active functional groups such as unsaturated bonds are oxidized. This is not to be done.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 2.0 g of geraniol and hydrated ruthenium dioxide (RuO ₂・XH ₂ O, water content 27.5%, Ru 55%)
(manufactured by Alfa Products) 50 mg was heated and stirred at 55 to 60° C. for 12 hours under an oxygen atmosphere of 1 atmosphere. The reaction mixture was applied to a silica gel column and flushed with dichloromethane to obtain 930 mg of citral and 370 mg of geraniol.

Example 2 In a solution of 2.0 g of geraniol dissolved in 8 ml of dichloromethane, 50 mg of hydrated ruthenium dioxide () powder similar to that used in Example 1 was suspended,
The mixture was heated and stirred at 90 to 95°C for 3 hours under an oxygen atmosphere (7 atm). The reaction mixture was purified by GLC (XF60 20%, 2m,
Analysis at 160°) revealed that 50.5% of geraniol was converted to citral (trans:cis=93:7).

Example 3 10 parts of geraniol, 1 part of ruthenium dioxide similar to that used in Example 1, 0.1 part of 2,6-di-t-butyl-p-cresol and 5 parts of toluene were heated to the reflux temperature of toluene. Oxygen gas was bubbled in for 1.2 hours while stirring. Analysis of the reaction mixture by GLC, NMR, and TLC revealed that 71% citral was produced. The remainder was essentially geraniol containing a small amount of nerol.

Example 4 A methylene chloride solution (approximately 5 ml) of ruthenium tetroxide prepared from 50 mg of the same hydrous ruthenium dioxide used in Example 1 was added to 15 g of geraniol with stirring. (Ruthenium dioxide is essentially produced in this state.) This was diluted with 80 ml of methylene chloride, and in the presence of 50 mg of 2,6-di-t-butyl-p-cresol, an oxygen atmosphere (4
-5 atm) at 85 to 90°C for 6 hours with stirring. The reaction mixture was analyzed in the same manner as in Example 3, and it was found that 14% of geraniol was converted to citral.

Example 5 A methylene chloride solution (about 15 ml) of ruthenium tetroxide prepared from 145 mg of ruthenium dioxide was added to 50 g of geraniol. 500 mg of 2,6-di-t-butyl-p-cresol was added to this, and the reaction temperature was 60
The mixture was heated and stirred at ~75°C for 11.5 hours in an oxidizing atmosphere of 8.5 atm. The reaction mixture was analyzed in the same manner as in Example 3, and it was found that 36% of geraniol was converted to citral.

Example 6 50 mg of hydrated ruthenium dioxide similar to that used in Example 1 and 1.0 g of carveol were added to 2 ml of methylene chloride.
Soak at 65-70℃ under oxygen (1 atm) atmosphere.
The reaction was allowed to proceed for 48 hours. When the reaction mixture was separated and purified using silica gel column chromatography, 34
Carvone was obtained with a yield of 1.5%, and unreacted carveol was quantitatively recovered.

Example 7 50 mg of hydrated ruthenium dioxide similar to that used in Example 1 and 50 mg of 2,6-di-t-butyl-p-cresol were added to 10.0 g of prenol, and the mixture was heated at 100°C under an oxygen atmosphere of 7 atm. The mixture was heated and stirred for hours. A portion of the reaction mixture was diluted approximately 50 times with carbon tetrachloride,
Filtration to remove the catalyst and NMR spectroscopy of the solution revealed that 27% of the prenol had been converted to 3-methyl-2-butenal. Note that, other than the aldehyde mentioned above, there was virtually no change in prenol.

Claims (1)

[Claims] 1. In the presence of a ruthenium dioxide () catalyst, the general formula A general formula characterized by dehydrogenating an unsaturated alcohol represented by using oxygen gas. A method for producing an unsaturated carbonyl compound represented by (wherein R ¹ , R ² , R ³ and R ⁴ are hydrogen, an alkyl group, an alkenyl group or an aryl group).