JPH0140024B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an efficient method for producing acyl cyanides, and more particularly, to a novel method for producing acyl cyanides, which comprises treating cyanohydrin with a hydroperoxide in the presence of a ruthenium catalyst for oxidative dehydrogenation. be. Acyl cyanides themselves are known as pesticides that have insecticidal and bactericidal effects (Ger.
Offen.1813184), and its usefulness as a highly selective acylating agent [D. Seebach et al.
Chem.Ber., 111 , 2630 (1978), AS, Howard
et al., Tetrahedron Letters, 1979 , 1339]. Acyl cyanides are important as intermediates for the synthesis of many useful heterocyclic compounds [J. Thesing,
Angew .
-It is an important group of compounds that can be derived into keto acids, α-aminoketones, 1,2-aminoethanol derivatives, arylacetic acid derivatives, etc. Conventionally, such acyl cyanides are produced by cyanating acid halides, but
The cyanation methods in this case include (1) a method using a stoichiometric amount or more of silver or copper cyanide, (2) a method using dry hydrogen cyanide in the presence of pyridine, and (3) a method using dry hydrogen cyanide in the presence of pyridine.
(4) using sodium cyanide in the presence of an ammonium salt as a phase transfer catalyst; (5) using organosilicon cyanide. However, methods (1) to (3) not only require high temperatures and a long time, but also often produce so-called acyl cyanide dimers as by-products, resulting in low yields. , On the other hand, method (4) also
It has the disadvantage of producing 30 to 50% dimer as a by-product, and although the method (5) provides acyl cyanide at a relatively low temperature and high yield, the organic cyanated silicon compound used as the cyanating agent is sensitive to moisture. Because it is extremely unstable and reacts with moisture to generate toxic hydrogen cyanide gas, the reaction system must be dehydrated strictly, which poses handling difficulties. In view of the above circumstances, the present inventors proposed a new method for cyanating acid halides (Japanese Patent Publication No. 57-35883, Japanese Patent Publication No. 57-77661). However, conventional methods, including these new cyanation methods, use highly reactive acid halides as starting materials, so they have the disadvantage that the range of acyl cyanides that can be produced is limited.
Moreover, acid halides are generally expensive. As described above, the conventional method cannot be said to be a general or industrially advantageous method, and it must be said that it includes various drawbacks. As a result of intensive research in order to overcome such problems in conventional methods, the present inventors have discovered that the dehydrogenation reaction of cyanohydrins, which can be easily produced from readily available aldehydes, can be used to produce various hydroperoxides in the presence of a ruthenium catalyst. The inventors have discovered the novel fact that the process progresses rapidly under mild conditions by the action of a similar compound, and based on this discovery, they have completed the present invention. That is, according to the present invention, a novel method for efficiently producing acyl cyanides using cyanohydrins, which are easily produced industrially, as raw materials is provided. The cyanohydrins that are the raw materials of the present invention have the general formula

It has a structure represented by [Formula], that is, aldehyde cyanohydrin, and the type is not limited as long as R ¹ is unsaturated aliphatic, aromatic, or heteroaromatic. Therefore, in the cyanohydrin of the above general formula, the organic group represented by R ³ includes an aryl group such as a phenyl group or a naphthyl group, a heterocyclic group such as a furyl group, a thienyl group, a pyrrolyl group, an indolyl group, or a pyridyl group; vinyl, propenyl.
Organic groups such as alkenyl groups such as isopropenyl and β-styryl are included, and any functional group may be bonded except for those that inhibit the progress of the reaction. Note that the above organic groups are merely examples and are not limited thereto. It is widely known that these cyanohydrins can be easily obtained from the corresponding aldehydes (having a structure in which R ¹ in the general formula of cyanohydrin is bonded to a formyl group), and these aldehydes can also be obtained by oxidation reaction ( R ¹ - CH ₃ → R ¹ CHO), hydrolysis of gem-dihalides (R ¹ CHX ² → R ¹ CHO), carbonylation of halides (R ² X → R ¹ CHO), Vilsmeyer
It is easy to produce industrially in large quantities by reaction (R ¹ H→R ¹ CHO), Gatterman-Koch reaction (R ¹ H→RCHO), etc. The hydroperoxide represented by the general formula R ² OOH (R ² is the same as above) used in this reaction may be any one as long as it falls within the range of R ² above, but considering chemical stability,
A secondary or tertiary carbyl group that is bonded to the hydroperoxide group is preferable, and examples of such organic group ^R2 include isopropyl group, cyclohexyl group, t-butyl group, α-tetralyl group, α-methylbenzyl group. group, α-cumyl group, α-simyl group [o-, m-, p-;

[Formula]], p-phenylene diisopropyl group

Examples include [Formula]. This reaction is carried out in the presence of a ruthenium catalyst, and any ruthenium metal or compound in which the valence of ruthenium is zero to trivalent can be used as the ruthenium catalyst. In this case, the ruthenium metal or compound can be supported on an inert carrier such as alumina, silica gel, activated carbon, etc. by a known method. Examples of ruthenium compounds used in this reaction include metal ruthenium powder, colloidal ruthenium, activated carbon-supported ruthenium, ruthenium carbonyl, (1,3,5
-cyclooctatriene)(1,5-cyclooctadiene)ruthenium, ruthenium dichloride,
Ruthenium dibromide, ruthenium oxide, ruthenium acetylacetonate, ruthenium trichloride, ruthenium tribromide, ruthenium triiodide, dichlorotricarbonyl ruthenium dimer, dichloro-π-benzene ruthenium
DMSO adduct, tristriphenylphosphine ruthenium dichloride, tristriphenylphosphine ruthenium dibromide, chlorohydrido tristriphenylphosphine ruthenium, bromohydrido tristriphenylphosphine ruthenium, tristri(p-chlorophenyl)phosphine ruthenium dichloride, Examples include tristriphenylphosphine ruthenium hydride acetate, tristriphenylphosphine ruthenium hydrido bivaroate, tristriphenylphosphine chlorodiphenylsilylruthenium hydride, and the like. Note that the amount of these ruthenium catalysts used is a so-called catalytic amount, and depending on the structure of cyanohydrin, it is possible to obtain acyl cyanides sufficiently quickly at room temperature even with an amount of about 1/1000 molar ratio. I can do it. Although this reaction proceeds without a solvent, it can also be carried out in an inert solvent. Examples of such solvents include benzene, toluene, acetone,
Dichloromethane, hexane, water, acetic acid, ethyl acetate, acetonitrile, t-butyl alcohol. Chlorbenzene, ether, tetrahydrofuran,
Examples include commonly used solvents such as sulfolane. The reaction of the present invention often proceeds rapidly even at room temperature, and depending on the structure of the cyanohydrin, cooling may be required to remove heat generation, but if the reaction rate is slow, it may be carried out under heating. Done,
It is usually carried out at a temperature range of -20°C to +100°C, preferably 0°C to 80°C. The relationship between the amounts of cyanohydrin and hydroperoxide is such that the reaction will proceed even if either is in excess.
Usually carried out at a molar ratio of cyanohydrin/hydroperoxide in the range of 0.1 to 2, preferably 0.2.
~1. To separate the product, add a solvent that is substantially insoluble in water to the reaction mixture as necessary, and in the case of an insoluble catalyst, remove the insoluble matter by filtration, centrifugation, etc., and then add water (if necessary). After washing the organic layer with a solvent (which may contain a reducing agent) and stripping the organic layer of the solvent if necessary, the separation can be easily carried out by conventional separation operations such as distillation, chromatography, or recrystallization. As described above, according to the present invention, a wide range of acyl cyanides, regardless of whether they are unsaturated aliphatic, aromatic, or heterocyclic, can be produced under mild conditions by using a wide range of easily available cyanohydrins as raw materials. It can be obtained in good yield. The desired acyl cyanide can be easily obtained without requiring complicated reaction operations or product separation, and can be said to be an extremely advantageous method from an industrial standpoint. Next, a more detailed explanation will be given based on examples. Example 1 48 mg (5 x 10 ^-2 mmol) of dichlorotritriphenylphosphineruthenium and 0.59 ml (5 mmol) of mandelonitrile were added to 5 ml of benzene under a nitrogen atmosphere.
of t-butyl hydroperoxide (70%) and stirred at room temperature.
ol) was added dropwise over 10 minutes, and stirring was continued for 50 minutes. 391 mg of diphenyl ether was added as an internal standard, and analysis by gas chromatography revealed that benzoyl cyanide was produced in a yield of 92.9%. Repeat the exact same reaction, add the reaction solution to 20 ml of ether without adding diphenyl ether, and add 5 ml of water.
ml twice, dried over magnesium sulfate, filtered, and distilled the solvent from the filtrate using a rotary evaporator. The remaining oil was purified by silica gel chromatography (developing solvent: hexane-benzene, gradient) and purified with methylene chloride. - As a result of recrystallization from a mixed solvent of pentane, pure benzoyl cyanide with a mp of 32.4-33.2℃ was obtained. Examples 2 to 11 Table 1 shows the results of reactions of other cyanohydrins in exactly the same manner as in Example 1. Yields were determined by gas chromatography unless otherwise specified. Note that Table 1 also shows the results of Example 1.

【table】

[Table] *The numbers in parentheses indicate the isolated yield.

Claims (1)

[Claims] 1. A cyanohydrin represented by the general formula [Formula] (wherein R ¹ represents an organic group selected from an aryl group, an alkenyl group, and a heterocyclic group) in the presence of a ruthenium catalyst. Below, general formula R ² OOH
(In the formula, R ² represents an organic group selected from an alkyl group, a cycloalkyl group, and an ^aralkyl group ⁾ . is the same as above).