DD160221A3 - PROCESS FOR PREPARING CRYSTALLINE-LIQUID TRANS-6-ALKYLDECALIN-2-CARBOXYLIC ACID ESTERS - Google Patents

Abstract

The invention relates to a novel process for the preparation of crystalline trans-6-n-alkyldecalin-2-carboxylic acid esters. The aim of the invention is the preparation of the crystalline liquid trans-6-n-alkyldecalin-2-carboxylic esters in high yields from easily accessible starting materials. It has been found that crystalline trans-6-n-alkyldecalin-2-carboxylic acid esters of the general formula can be prepared by catalytic high-pressure hydrogenation of 6-n-alkylnaphthalene-2-carboxylic acids, separation of the trans isomers by distillation and esterification of Reaction with thionyl chloride obtained acid chlorides with the corresponding hydroxy compounds.

Description

224 160

Process for the preparation of crystallin-iTissigrr trans-Gn- Alk yldecal in-2-carboxylic acid ester

in the field of the invention

The invention relates to a novel process for the preparation of crystalline trans-6-n-alkyldecalin-2-carboxylic acid esters. These substances can be used in electro-optical components.

Characteristic of the known technical solutions

It is known that hydrogenation of naphthalene-2-carboxylic acid with platinum dioxide in glacial acetic acid at 240 atms gives rise to the non-mesogenic cis-decalin-2-carboxylic acid (W. Dauben, E. Hoerger, J. Araer, Ohem, Soc. 72 »1504 (1951)). However, only unsubstituted decalcarboxylic acids are obtainable in this way. All hydrogenation experiments with Raney nickel in alkaline medium under high pressure led to the 5,6,7,8-tetrahydronaphthalene-2-carboxylic acid (G. Stork, J. Araer, Chem. Soc., 6_9, 576 (1947)) Only the synthesis of trans-decalin-2-carboxylic acid from trans-decalin was achieved by chlorination and subsequent Grignard reaction (1st N.B.B., Chapman, J. Shorter, KJ Toine, J. Chem. Soc., 1964 , 1077 2. W.Dauben, R. Tweit, J.Amer.Chem. Soc., 76, 3197 (1954)).

Furthermore, it has already been proposed (GB 2082179) DD 156258) to produce 6-alkyldeealin-2-carboxylic acids and their esters by the following processes:

Either a 4-subst.-cyclohexanone is first mixed with pyrrole

- Jler

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lidin and then reacted in 6 v / eiteren synthesis steps to 6-substituted decalin-2-carboxylic acid, or starting from tetrahydronaphthal-6-one, 6-alkyl-tetrahydronaphthalene-2-ca'rbonsäure is prepared in 5 synthetic steps, which subsequently must be hydrogenated. Both variants suffer from the disadvantage that the individual synthesis steps are not quantitative and thus result in only low yields due to the large number of synthetic steps.

 ^ -224 160

Object of the invention

The object of the invention consists in the easier preparation of the crystalline liquid trans-o-n-alkyldecalin ^ -carboxylic acid esters in high yields from Mcht accessible starting materials.

Explanation of the essence of the invention

The object of the invention is a new process for the preparation of crystalline liquid 6-n-alkyldecalin-2-carboxylic acid esters.

According to the invention, crystalline-liquid trans-6-n-alkyldecalin-2-carboxylic acid esters of the general formula

"xxx

C-O-R

ν. with R

R ² =

- ° ^COOG n ^H 2n ₊ 1 '- ^SC n ^H 2n ₊ 1

-Cl, -Br, -CN, -NO ,.

with η = 1 to 12. R ⁴ '= -H, -Cl, -C ₂ H ₅

prepared from 6-n-alkylnaphthalene ~ 2-carboxylic acids which hydrogenated in alkaline solution with Raney-Hickel catalysts under high pressure v / earth, the trans-isomers are separated in a known manner by distillation and then reacted in a known manner with thionyl chloride * and the resulting acid chlorides esterified with the corresponding hydroxy compounds.

2 2 4 1 6 0

The naphtha compounds required as starting materials can be prepared in a known manner (D. Coates, GG, W. Gray, Mol. Cryst., Liqu., Cryst., 21, 249 (1976)). Thereafter, 6-n-alkylnaphthalene-2-carboxylic acids by Friedel-Crafts acylation of naphthalene, subsequent reduction dea ketone Huang Minlott with hydrazine hydrate, Friedel Crafts again acylation of the resulting 2-n-acylnaphthalenes with acetyl chloride or acetic anhydride and oxidation of 6'-n-alkyl 2'-acetonaphthone obtained with Alkalihypobromid.

example 1

34 g (0.15 mol) of 6-n-butylnaphthalene-2-carboxylic acid are hydrogenated together with 20 g of KOH in 150 ml of water and 10 g of catalyst at 14 MPa and at temperatures between 200 and 260 ⁰ C for 100 hours in a Schüttelautoklaven. The potassium salt of decalinic acid is produced as a foam. After two hours of cooking with conc. HCl deposits the crude acid as a pale yellow oil on the solution. This is taken up in ether, over Na ₂ SO. dried and fractionally distilled. Bp: 172 ° C / 40 Pa; Yield 60 to 70 % of theory.

The remaining 6-n-alkyldecalin-2-carboxylic acids are prepared analogously by using the corresponding 6-n-alkylnaphthalene-2-carboxylic acids in the hydrogenation.

Example 2 Preparation of δ-n-butyldecane

23.8 g (0.1 mol) of 6-n-butyldecalin-2-carboxylic acid are mixed with 5 times the amount of thionyl chloride (40 ml). After addition of 100 ml of ether and a few drops of pyridine, it is refluxed gently for 6 hours , After stripping off the ether and the remaining thionyl chloride is fractionated

2 2Λ160

Bp: 127 to 128 ° C / 40 Pa; Yield: 80 to 90 % of theory.

The other G-n-Alkyldecalin ^ -carboxylic acid chlorides are obtained according to the same procedure by using the appropriate acids ·

Example 3

Preparation of ^ - / ^ o ^ n-Alkyldecal ^^ g-carbonyloxy 77'benzqe ^

The required 4-hydroxybenzoic acid phenyl esters are prepared according to literature procedures (J.P. van Meter, B.H.

Klanderman, Mol, Gryst. Liq. Cryst. 22, 285 (1973)).

4-Hydro3ybenzoesäure p-Cyanphenylester obtained by esterification of Benzyloxyearbonyloxybenzoylchlorid with 4-cyanophenol and subsequent catalytic deprotection by hydrogen in the presence of Pd / SrCO, as a catalyst.

The following new variant proved to be even more favorable for the synthesis of substituted 4-hydroxybenzoic acid phenyl esters: 8 g (0.023 mol) of 4-n-butyldecalin-2-carboxylic acid 4- ^l- formylphenyl ester are dissolved in 20 ml of 90% acetic acid.

For this purpose, 5 g of 0r0 ~ are added dropwise in 10 ml of 60% acetic acid and then stirred at 4O ⁰ C for 12 hours. After cooling, 50 ml of water are added, the precipitate precipitated was taken up in ether, the ether extract was washed with water and bicarbonate solution and dried over Na 2 SO 4. dried.

After removal of the solvent, the crude crude acid is converted into the acid chloride without further purification.

The esterification takes place in the variant according to EINHORN

0.005 mol of the respective substituted phenol or 4-Hydroxybenzoesäurephenylesters in 20 ml of pyridine are mixed with the equimolar amount of 6-n-alkyldecalin-2 - carboxylic acid chloride or 4- / ~ 6-n-alkyldecalin-2-carbonylo? YJ7-benzoyl chloride. The mixture is allowed to stand overnight and then heated to 70 ⁰ O for 30 min. After cooling

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is concentrated on 60 g of ice and 13 ml of conc. Sulfuric acid poured, the precipitate sucked off, washed with aqueous arο arbonate solution, water, dilute hydrochloric acid and washed again with water.

After recrystallization from absolute methanol or ethanol for 3 to 5 times, the esters are obtained as pure and clear as a clarifier.

Yields are between 30 and 70 % of theory. The substituted phenyl and cyclohexyl esters are not mesomorphic.

Table 1

R-

Cl

, 70-71. 139-140. 246-249.

OC ₇ H _{15 °.} 62-63. 159-160. 215-216.

OC ₇ H _{15 °.} 78-80. , 200.5

C ₅ H ₁₁ . 67-69. 150-151. 222-224.

CN. 100-101 -. 294-296.

(Dec.)

K = crystalline-solid S smectic

Example 4

Nematic I β isotropic-liquid

Other esters of 6-n-alkyldeQaJ.sub.2-2-carboxylic acid are obtained when esterified with hydroxybiphenyl and other analogous hydroxy compounds of Example Jf. Table 2 shows the transformation temperatures of the compound obtained.

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!Table

6-n-Alkyldecalin-2-carboxylic acid 4-substituted biphenyl ester and analogous esters

COO-X-R

H ₉ C ₄

O-0--

br

_t 61- 63 - -

164-166.

, 126-128. 177-179. 266-267.

^C 5 ^H 11. 93- 94 - -

, 218-219 ♦

, 104-105. 208-209. 237-238

OC ₉ H _19th 65-66. 189-190

97

Claims (1)

224 Process for the preparation of crystalline trans-6-alkyldecalin-2-carboxylic acid esters of the general formula ,1 C-O-R ' 1
where R = n-alkyl ^R = = " ^G n ^H 2n ₊ 1 '- ^0C n ^H 2n ₊ 1' - ° ^COOC n ^H 2n ₊ 1 '- ^SC n ^H -Cl, -Br, -CN, with η = 1 to 12 mean, -Cl, - characterized in that 6-n-alkylnaphthalene-2'-carboxylic acids are hydrogenated in alkaline solution with Raney-Kickel catalysts under high pressure, the trans-isomers separated in a known manner by distillation and then reacted in a known manner with thionyl: and the resulting Acid chlorides are esterified with the corresponding hydroxy compounds.