JP2867368B2 - Method for producing cyclohexanol derivative - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a cyclohexanol derivative useful as a raw material for a liquid crystal material as an electrochemical display material.

[Prior Art] A liquid crystal display cell that is currently the mainstream is a TN cell, which is a type of field effect cell. Cryst. Liq. Cryst. 63, 45 (198
As reported in 1), the anisotropy (縞 n) of the refractive index of the liquid crystal material filled in the cell is used to prevent the occurrence of interference fringes on the cell surface, which may impair the appearance of the cell. It is necessary to set the product of the thickness (d) μm of the liquid crystal layer in the cell to a specific value. The thickness of the liquid crystal layer in a liquid crystal display cell that is practically used is usually set to a certain value within a limited range of 6 to 10 μm.
When set to 5, a liquid crystal material with a small value of Δn is required, and when a value of Δn · d is set to 1.0, 1.6 or 2.2, conversely, a liquid crystal material with a large value of Δn is required Becomes As described above, Δn depends on the display characteristics of the liquid crystal display cell.
A liquid crystal material having a small value and a large liquid crystal material are required.

On the other hand, most practical liquid crystal materials are usually prepared by mixing a compound having a nematic phase near room temperature and several or more components of the compound having a nematic phase in a temperature range higher than room temperature.

Many of the mixed liquid crystals as described above that are currently in practical use are:
Since it is required to have a nematic phase over at least the entire temperature range of −30 ° C. to + 65 ° C., there is a need for a liquid crystal having a nematic phase near or above room temperature, and many reports have been made. ing.
Such useful liquid crystals are all liquid crystals having a cyclohexane ring in the molecule.
No. 2-39497, Tokuhei 2-37333, Tokubo Sho64
No. 935, JP-B-63-55496, JP-B-63-53178, JP-B-63-46742, JP-A-2-36153, JP-A-2-3613
3, JP-B-64-22835 and JP-A-63-287737.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is to reduce the value of Δn of the mixed liquid crystal by adding it to a nematic mixed liquid crystal which is currently practically used as a base liquid crystal, Provided is a cyclohexanol derivative useful as a raw material compound, which can be used for a liquid crystal having a cyclohexane ring capable of increasing a nematic phase / isotropic liquid phase transition temperature which is an upper limit of a temperature range showing a phase. It is in.

[Means for Solving the Problems] That is, the present invention provides: 1. a general formula (II): (Wherein, X represents a halogen atom or —OSO ₂ C ₆ H ₄ CH ₃ ; n represents an integer of 1 to 10), and after condensation with alcohols, nuclear hydrogenation is performed. Formula (I): (Wherein, R is an alkyl group having 1 to 5 carbon atoms which may contain an asymmetric carbon, and n is the same as described above).

 Hereinafter, the present invention will be described in detail.

The cyclohexanol derivative represented by the general formula (I) is, for example, a compound (IV): (Wherein n is the same as described above) can be synthesized by the following steps.

After protecting the phenolic hydroxyl group of the compound represented by the general formula (IV) with benzyl bromide, the ester group in the compound is reduced to an alcohol represented by the general formula (V) using a reducing agent. The reducing agent used at this time is not particularly limited, and various known agents capable of reducing an ester group can be used. For example, LiAlH ₄ , NaAlH ₂ (OCH ₂ CH ₂ OCH ₃ ) ₂ , LiBH _{4 and the} like are economically advantageous. It is. The amount of the reducing agent to be used is about 1 to 4 mol per 1 mol of the substrate represented by the general formula (IV),
Preferably 2.0 to 3.5 moles are used. The solvent used in the reduction reaction is not particularly limited as long as it is not an alcohol-based solvent, but benzene, ether, toluene,
Xylene, tetrahydrofuran, hexane are preferred.

Next, the alcohol represented by the general formula (V) can be prepared by a known method, for example, P. Hodge, et.al., JCS. PerkinI (1984), 195,
RTHrubiec, J. Org. Chem., (1984), 49, Compound (II) can be derived by halogenation or tosyl chloride tosyl ester.

Next, the compound (II) is condensed in the presence of an alcohol and a basic substance to be described later to give the compound (III)
Can be manufactured. Examples of the basic substance used in the above reaction include alkali metal hydrides such as potassium hydride and sodium hydride; alkali metals such as lithium, sodium and potassium; alkali metal alcoholates such as sodium ethylate and sodium methylate; and carbonates. Examples thereof include alkali metal carbonates such as sodium and potassium carbonate. The alcohols used in the above reaction include methanol, ethanol, propanol, butanol, (S) -2-butanol, (R) -2-butanol, (S) -2-pentanol, and (R) -2. -Pentanol and (S) -2-methyl-1-butanol. The amount of the basic substance to be used is usually at least one equivalent to the alcohol used, and the upper limit thereof is not particularly limited, but is preferably about three equivalents. The equivalent ratio of the amounts of the alcohols and compound (II) used is about 1: 5 to 5: 1, preferably 1: 3 to 3: 1. In the above reaction, the reaction temperature is usually in the range of about -50 ° C to 120 ° C, preferably in the range of -30 ° C to 100 ° C. As a reaction solvent, for example, a solvent inert to the reaction such as tetrahydrofuran, diethyl ether, acetone, methyl ethyl ketone, toluene, benzene, chloroform, dimethylformamide or the like can be used alone or as a mixture, and the amount used is not particularly limited.

Next, by subjecting the obtained compound (III) to catalytic hydrogenation reaction, the cyclohexanol derivative (I) as the target compound can be obtained. Compound (III)
When performing catalytic hydrogenation of phenol, debenzylation occurs preferentially depending on the catalyst used, and the phenol derivative (V
The formation of compound (I), which is the object of the present invention, can be achieved by proceeding the reaction without isolating the compound (I).
Can be obtained.

The catalyst used for the hydrogenation reaction is not particularly limited, and a usual hydrogenation catalyst can be used. Preferred hydrogenation catalysts include, for example, palladium, platinum,
A material in which a metal such as ruthenium and rhodium is supported on various carriers such as carbon powder, zeolite, silica, and alumina corresponds to the above. The amount of the catalyst to be used is about 1 to 40% by weight, preferably 5 to 20% by weight, relative to compound (III). In the catalytic hydrogenation reaction, the hydrogen pressure
5Kg / cm ² ~200Kg / cm ^2, preferably about 40Kg / cm ² ~150Kg /
The reaction is preferably performed in the range of cm ² , in which case the presence or absence of the solvent is not considered.

There is no particular limitation on the solvent used, but ethyl acetate,
Preferred are tetrahydrofuran, ethanol, dioxane and the like. After completion of the catalytic hydrogenation reaction, the desired cyclohexanol derivative can be obtained by distillation under reduced pressure.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

Example 1 Synthesis of 4- (1′-methoxyethyl) -1-cyclohexanol (First Step) 150 g of methyl parahydroxyphenylacetate (0.
9 mol), 188 g (1.1 mol) of benzyl bromide and 248 g (1.8 mol) of anhydrous potassium carbonate were added to acetone 1 and the mixture was refluxed for 10 hours. After completion of the reaction, the precipitate was separated by filtration, sufficiently washed with acetone, and combined with the mother liquor and concentrated under reduced pressure. The residue was purified by silica gel chromatography (CHCl ₃ ),
Parabenzyloxyphenylacetic acid methyl ester 196g
(76% yield). NMR (CDCl ₃ ); δ (ppm) = 3.51
(S, 2H), 4.38 (s, 3H), 5.12 (s, 2H), 6.98 (d, 2H), 7.
35 (m, 5H), 7.98 (d, 2H) (2nd stage) To 800 ml of tetrahydrofuran (THF) was added 15 g (0.4 mol) of lithium aluminum hydride, and with stirring, 50 g (0.2 mol) of methyl methyl parabenzyloxyphenylacetate was added. It was dissolved in 200 ml of THF and added dropwise. At this time, the reaction was carried out with care so that the reaction temperature did not become 10 ° C. or higher. After the completion of the dropwise addition, the reaction was further carried out at room temperature for 15 hours. Then, THF was distilled off under reduced pressure, 500 ml of diethyl ether was added, and the mixture was washed sequentially with a 10% aqueous hydrochloric acid solution, water, and saturated saline. The organic layer was concentrated to obtain 35 g of parabenzyloxyphenylethanol (yield: 76%).

NMR (CDCl ₃ ); δ (ppm) = 1.60 (s, 1H), 2.85 (t, 2
H), 3.53 (t, 2H), 5.12 (s, 2H), 6.68 (d, 2H), 7.35
(M, 5H), 7.98 (d, 2H) (3rd stage) 50 g (0.21 mol) of parabenzyloxyphenylethanol was dissolved in 500 ml of carbon tetrachloride, and phosphorus tribromide was added dropwise at -10 ° C. After reacting for 10 hours at the same temperature, the reaction mixture was concentrated under reduced pressure, and 300 ml of diethyl ether was added.
Washed thoroughly with water. The organic layer was concentrated to obtain 43.5 g (yield: 71%) of 4-benzyloxy-1- (1'-bromoethyl) benzene. NMR (CDCl ₃ ); δ (ppm) = 2.78 (t, 2
H), 3.65 (t, 2H), 5.12 (s, 2H), 6.96 (d, 2H), 7.35
(M, 5H), 7.98 (d, 2H) (4th stage) In 500 ml of THF, 30 g (0.1 mol) of 4-benzyloxy-1 (1'-bromoethyl) benzene and 21 g of methyl iodide
(0.15 mol), 7.5 g of sodium methylate (0.15 mol)
Was added and the mixture was heated under reflux for 15 hours, and then the reaction mixture was concentrated under reduced pressure. The residue was purified by silica gel chromatography (CHCl ₃ ) to obtain 21 g of 4-benzyloxy-1- (1′-methoxyethyl) benzene (87% yield). NMR (CDCl ₃ );
δ (ppm) = 2.78 (t, 2H), 3.35 (s, 3H), 3.58 (t, 2H),
5.12 (s, 2H), 6.96 (d, 2H), 7.35 (m, 5H), 7.98 (d, 2
H) (5th stage) 4-benzyloxy-1- (1'-methoxyethyl)
50 g (0.2 mol) of benzene was dissolved in 100 ml of ethanol containing 0.5% (w / w) acetic acid, 5 g of 5% Ru-carbon powder was added, and the mixture was reacted in an autoclave at a hydrogen pressure of 80 kg / cm ² and 70 ° C. for 5 hours. . After filtering off the catalyst, the mother liquor was distilled, and a fraction at 97-98 ° C was fractionated at 4 mmHg to obtain 27 g of 4- (1′-methoxyethyl) -1-cyclohexanol (86% yield). NMR (CDC
l ₃ ); δ (ppm) = 0.98 (m, 1H), 1.15 to 1.80 (m, 10H),
1.95 (m, 1H), 3.30 (s, 3H), 3.37 (m, 2H), 3.52 (m, 0.5
H), 3.94 (m, 0.5H) Example 2 The same procedure as in Example 1 except that the catalyst was replaced with 5% Ru-carbon powder and 5% Rh-carbon powder was used, and the reduction reaction was carried out at normal temperature and pressure. Was performed to obtain 29 g of 4- (1'-methoxyethyl) -1-cyclohexanol (yield 92%). NMR analysis results were the same as in Example 1.

Example 3 The procedure of Example 1 was repeated, except that 84 g (0.5 mol) of methyl parahydroxyphenylpropionate was used instead of using methyl methyl parahydroxyphenylacetate. Propyl) -1-cyclohexanol 29 g (35% overall yield)
I got

_{NMR (CDCl 3); δ (} ppm) = 0.92 (m, 1H), 1.13~1.78
(M, 12H), 1.92 (m, 1H), 3.28 (s, 3H), 3.33 (m, 2H),
3.48 (m, 0.5H), 3.91 (m, 0.5H) Example 4 In Example 3, instead of using 5% Ru-carbon powder, 5% Rh-carbon powder was used, and the reduction reaction was performed at normal temperature and normal pressure. The same operation was carried out except that 30 g of 4- (1′-methoxypropyl) -1-cyclohexanol (total yield: 36
%). NMR analysis results were the same as in Example 3.

Example 5 The procedure of Example 3 was repeated, except that 5% Pt-carbon powder was used instead of 5% Ru-carbon powder, and the reduction reaction was carried out at normal temperature and pressure. -Methoxypropyl) -1-cyclohexanol 25 g (total yield 30
%). NMR analysis results were the same as in Example 3.

Example 6 The same operation as in Example 1 was carried out except that sodium methylate was used instead of sodium methylate, to obtain 18 g of 4- (1′-ethoxyethyl) -1-cyclohexanol (total yield: 20%). ) Got. NMR (CDC
l ₃ ); δ (ppm) = 0.98 (m, 1H), 1.20 (t, 3H), 1.21 ~
1.80 (m, 10H), 1.95 (m, 1H), 3.37 (m, 2H), 3.47 (q.2
H), 3.52 (m, 0.5H), 3.94 (m, 0.5H) Example 7 In Example 1, instead of sodium methylate, (S) -2-pentanol and sodium metal were equimolarly in THF. 4- [1 ′-(1 ″), except that the alkoxide obtained by the reaction in
-Methylbutyloxyethyl)]-1-cyclohexanol 28g (total yield 25%) was obtained.

NMR (CDCl ₃ ); δ (ppm) = 0.88 (t, 3H), 0.98 (m, 1
H), 1.15 to 1.81 (m, 17H), 1.95 (m, 1H), 3.37 (m, 2H),
3.52 (m, 0.5H), 3.94 (m, 0.5H), 4.40 (m, 1H) Example 8 Synthesis of 4- (1'-methoxyethyl) -1-cyclohexanol 38.2 g of parabenzyloxyphenylethyl tosylate
(0.1 mol) was dissolved in 200 ml of THF, and a 100 ml THF solution of sodium methylate (0.15 mol) was added dropwise at 20 to 25 ° C. After the addition was completed, the mixture was further stirred at 40 to 50 ° C for 5 hours. After completion of the reaction, the mixture was concentrated under reduced pressure, and the residue was dissolved in chloroform.
After the organic layer was washed with a 0.1N sodium hydroxide solution and water in that order, the organic layer was concentrated under reduced pressure. 18 g of the obtained 4-benzyloxy 1- (1′-methoxyethyl) benzene
(Yield 75%) was subjected to catalytic reduction according to Example 1 to give 4-
(1'-methoxyethyl) -1-cyclohexanol 9.
5 g (85% yield) were obtained. NMR analysis results were the same as in the examples.

[Effects of the Invention] According to the present invention, the value of Δn of the mixed liquid crystal is reduced by adding it to various nematic mixed liquid crystals practically used as a base liquid crystal, and at the upper limit of the temperature range showing a nematic phase. There is a great effect that a cyclohexanol derivative useful as a liquid crystal material having a cyclohexane ring capable of increasing a certain nematic phase / isotropic liquid phase transition temperature can be easily provided.

Continuation of the front page (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 43/13 C07C 41/16 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A compound of the general formula (II): (Wherein, X represents a halogen atom or —OSO ₂ C ₆ H ₄ CH ₃ ; n represents an integer of 1 to 10), and after condensation with alcohols, nuclear hydrogenation is performed. Formula (I): (Wherein, R is an alkyl group having 1 to 5 carbon atoms which may contain an asymmetric carbon, and n is the same as described above).