JPH1087530A - Reduction of aldehyde or ketone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reducing an aldehyde or ketone, enabling to safely and easily reduce the aldehyde or ketone with a high selectivity and in a short time in the absence of a solvent or in a general inexpensive solvent by reacting the aldehyde or ketone with polymethylhydrosiloxane in the presence of a specific catalyst. SOLUTION: This method for reducing an aldehyde or ketone comprises reacting (B) an aldehyde or ketone with (C) polymethylhydrosiloxane of the formula [R<1> , R<2> are each H, methyl; (n) >=0] in the presence of (A) a catalytic amount of tetrabutyl ammonium fluoride. The component A is preferably used in an amount of usually 0.001-0.5 equivalent, especially 0.005-0.1 equivalent, based on the component B in the reaction, and the reaction easily proceeds even at a low temperature such as -70 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel aldehyde or ketone reduction method capable of safely and easily reducing a carbonyl group of an aldehyde or ketone.

[0002]

BACKGROUND OF THE INVENTION The production of alcohols by reduction of aldehydes or ketones is a very important industrial process, and various reports have been made on this production method. However, among them, a method using polymethylhydrosiloxane which is inexpensive as a reducing agent, is stable against air and moisture, and is easy to handle is a very effective method.

[0003] The method of using polymethylhydrosiloxane is a method in which an aldehyde or ketone is reduced by reacting it with polymethylhydrosiloxane, followed by desilylation to produce an alcohol. A method using a catalytic amount of an organotin compound as a siloxane activator (J. Lipowitz et al.
J. Org. Chem. , 38, 162-165 (19
73)), a method using potassium fluoride or potassium formate as an activator for polymethylhydrosiloxane (C.I.
Chuit et al., Synthesis, 1989, 981.
９８984) are known.

[0004] However, the former method has a problem that it is difficult to apply to industrial production because a toxic tin compound is used.
A large amount of polymethylhydrosiloxane activator is required,
Polar solvents such as expensive N, N-dimethylformamide and dimethylsulfoxide have to be used, and none of these methods has been satisfactory in industrial production.

The present invention has been made in view of the above circumstances, and provides a method for reducing an aldehyde or ketone in which the carbonyl group of the aldehyde or ketone can be safely and easily reduced using polymethylhydrosiloxane. With the goal.

[0006]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, as shown in the following reaction formula (A), aldehydes or ketones have the following general formula: By reacting the polymethylhydrosiloxane represented by (1) with a catalytic amount of tetrabutylammonium fluoride, the aldehyde or ketone can be reduced safely and easily in a solventless or inexpensive general-purpose solvent, and In a substrate in which an isomer such as cis-trans is produced by reduction, high selectivity is generally obtained at a low temperature, but the reduction reaction of the present invention has a very high activity,
Since the reaction easily proceeds even at a low temperature such as 70 ° C., it can be reduced with very high selectivity, and further, by subjecting the reduced product of the aldehyde or ketone obtained by the above method to desilylation, The present inventors have found that a corresponding alcohol can be easily obtained, and have accomplished the present invention.

[0007]

Embedded image (However, in the formula, R ¹ and R ² may be the same or different, and each is a hydrogen atom or a methyl group, and n is an integer of 0 or more.)

Accordingly, the present invention provides a method for reacting an aldehyde or ketone with a polymethylhydrosiloxane represented by the above general formula (1) in the presence of a catalytic amount of tetrabutylammonium fluoride to form a carbonyl group of the aldehyde or ketone. And a method for reducing an aldehyde or ketone.

Hereinafter, the present invention will be described in more detail. In the method for reducing aldehyde or ketone of the present invention, the aldehyde or ketone used as a raw material includes:
Various aldehyde compounds and ketone compounds can be used, and these compounds may be any of aliphatic, alicyclic and aromatic compounds. That is, it may have a carbon unsaturated bond, and may further have a hydrogen atom bonded to a carbon atom partially or wholly substituted with a halogen atom or the like, and a carbon atom such as an oxygen atom Any aldehyde or ketone which has a different atom or a group containing a different atom, may have a carbonyl group, and can be conventionally reduced by reacting with polymethylhydrosiloxane can be used.

The polymethylhydrosiloxane to be reacted with an aldehyde or ketone is represented by the following general formula (1).

[0011]

Embedded image

In the above formula (1), R ¹ and R ² may be the same or different and each is a hydrogen atom or a methyl group, and n is an integer of 0 or more, preferably 0 to 1,0.
It is an integer of 00.

The amount of the polymethylhydrosiloxane of the above formula (1) is determined based on the amount of S based on the substrate aldehyde or ketone.
One equivalent or more, particularly preferably 1 to 5 equivalents, is preferable in terms of iH unit. If the amount used is less than 1 equivalent, the reduction reaction may not be completed.

Further, tetrabutylammonium fluoride is used as a catalyst for activating polymethylhydrosiloxane, and may be used in a catalytic amount relative to the substrate aldehyde or ketone. 0.001 to 0.5 equivalent, especially 0.00
5 to 0.1 equivalents are preferred. If the amount is less than 0.001 equivalent, a satisfactory effect may not be obtained.
Even if it is used in excess of 5 equivalents, a high effect cannot be expected, resulting in high cost and economic disadvantage.

The reduction reaction according to the present invention is a method of adding tetrabutylammonium fluoride to a mixture of the raw material aldehyde or ketone and the polymethylhydrosiloxane of the above formula (1), Either a method of adding polymethylhydrosiloxane to the mixture or a method of adding aldehyde or ketone to a mixture of polymethylhydrosiloxane and tetrabutylammonium fluoride is possible.

In the above-mentioned reduction reaction, a solvent is not essentially required, but a general-purpose solvent such as tetrahydrofuran (THF) or diethyl ether may be used if necessary when the stirring property is poor.

Although the reaction conditions for the above-mentioned reduction reaction are not particularly limited, the reaction of the present invention has a very high activity, and the reaction easily proceeds even at a low temperature such as -70 ° C.

After the carbonyl group of the starting aldehyde or ketone is reduced by the method of the present invention, the resulting reaction solution is treated directly or with a fluoride such as potassium fluoride, tetrabutylammonium fluoride or the like. Decomposition or alcoholysis with methanol or the like and desilylation can easily provide an alcohol in which the carbonyl group C ＝ O of the raw material aldehyde or ketone is reduced to C—OH.

[0019]

According to the method for reducing aldehydes or ketones of the present invention, aldehydes or ketones can be reduced safely and easily in a solventless or inexpensive general-purpose solvent. In the case of a substrate in which an isomer such as cis-trans is produced by reduction, high selectivity is generally obtained at low temperatures, but the reduction reaction of the present invention has a very high activity, Since the reaction proceeds easily even under, reduction can be performed with very high selectivity. Furthermore, the corresponding alcohol can be easily obtained by subjecting the reduced product of the aldehyde or ketone obtained by the method of the present invention to desilylation.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

Example 1 p-tert-butylcyclohexanone 308 was placed in a 10 ml flask equipped with a thermometer.
mg (2 mmol), polymethylhydrosiloxane 18
0 mg (1.5 molar equivalent in terms of Si-H) and THF4m
After cooling to −70 ° C., 1M of tetrabutylammonium fluoride was stirred with a magnetic stirrer.
0.1 ml of a tetrahydrofuran solution was added and reacted for 30 minutes. 2 ml of a 1 M THF solution was added to the reaction solution, and the mixture was heated to room temperature, poured into a vessel containing diethyl ether and saturated saline, and adjusted to pH 2 with 1N hydrochloric acid. The ether layer was separated by liquid separation, neutralized with sodium hydrogen carbonate, dehydrated with magnesium sulfate, and the solvent was removed under reduced pressure. The obtained solid was purified by silica gel chromatography to obtain 269 mg of p-tert-butylcyclohexanol. Obtained. The yield was 86% and the trans: cis ratio was 96: 4.

Examples 2 to 8 Using the various carbonyl compounds shown in Table 1, the reaction was carried out in the same manner as in Example 1. Table 1 shows the results.

[0023]

[Table 1]

Example 9 Citronellal 598 mg (3.8 mmol) was placed in a 10 ml flask equipped with a thermometer.
l), 350 mg of polymethylhydrosiloxane (Si-
H equivalent 1.5 mol equivalent) and THF 8 ml, and
After cooling to ５5 ° C., 0.2 ml of a 1 M THF solution of tetrabutylammonium fluoride was added with stirring with a magnetic stirrer, and reacted for 15 minutes. THF was removed from the reaction solution under reduced pressure, and the residue was dissolved in a mixed solution of 8 ml of diethyl ether and 8 ml of acetone. Then, 1.13 g (19 mmol) of potassium fluoride was added thereto, followed by stirring for 3 hours. After the obtained liquid was filtered, the filtrate was purified by silica gel chromatography in which the filtrate was concentrated to obtain 541 mg of citronellol. The yield was 89%.

Example 10 The reaction and post-treatment were carried out in the same manner as in Example 9 except that citronellal was changed to 3-phenylpropanal, to obtain 3-phenylpropanol in a yield of 85%.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07C 33/20 C07C 33/20 33/30 33/30 33/32 33/32 35/08 35/08 35/29 35/29 67/31 67/31 69/675 69/675 // C07B 61/00 300 C07B 61/00 300

Claims (1)

[Claims] An aldehyde or ketone is reacted with a polymethylhydrosiloxane represented by the following general formula (1) in the presence of a catalytic amount of tetrabutylammonium fluoride to reduce the carbonyl group of the aldehyde or ketone. A method for reducing an aldehyde or a ketone, comprising: Embedded image (However, in the formula, R ¹ and R ² may be the same or different, and each is a hydrogen atom or a methyl group, and n is an integer of 0 or more.)