DD252828A1 - PROCESS FOR PREPARING CRYSTALLINE-LIQUID TRANS-4- (TRANS-5-SUBST.-1,3-DITHIAN-2-YL) -CYCLOHEXANCARBOXYANESE - Google Patents

Abstract

The invention can be used in the chemical industry for the production of liquid crystals. Liquid crystals are used in optoelectronic devices to display numbers, characters and images. The aim of the invention is the preparation of novel crystalline liquid trans-4- (trans-5-Subst.-1,3-dithian-2-yl) cyclohexanecarboxylic acid esters. Crystalline-liquid trans-4- (trans-5-Subst.-1,3-dithian-2-yl) -cyclohexanecarboxylic acid esters have been found to be preparable by the slow addition of 2-subst.-propane-1,3-dithiols a boiling solution of trans-4-formyl-cyclohexanecarboxylic acid esters and an acidic catalyst such as p-toluenesulfonic acid or boron trifluoride in a suitable solvent with CHCl3 or benzene, wherein the water of reaction formed is simultaneously distilled off and a separation of the pure trans isomer by fractional crystallization from methanol succeed.

Description

COOY

with η = 1 ... 12

- (θ) - / "Vr ^1. cholesteryl. -

with m = 2 .., 8

, -CH-Cp-H

I D Ιό

CH,

R ³ = R ¹ , OR ¹ , COOR ¹ , OOCR ¹ , OCOOR ¹ , COR ¹ , CN, halogen R ⁴ , R ⁵ = H, H / CH ₃ , H / H, CH ₃ / CN, H / H, CN / CN, CN when R ³ Φ CN R ⁶ = OR ¹ , CH ₂ OR ¹ , CN, halogen, COOR ¹ , OCOR ¹ with X = -COO-, OOC-, single bond Y = Q, S, Z = O , P

and η = 1 to 12.

Characteristic of the known technical solutions

Crystalline liquid substituted 1,3-dithianes are described in WP 160061 and DE 3133884. However, only in position-2 phenyl-substituted 1,3-dithiane and simple 2- (4-n-alkylcyclohexyl) -1,3-dithiane can be synthesized according to these methods, the scope of which is limited.

The synthesis of 4- (1,3-dithian-2-yl) cyclohexanecarboxylic succeeds by this method only in very poor yield and consequent lack of purity. The substances produced according to the invention are novel and processes for their preparation have hitherto not been described.

Object of the invention

The object of the invention is the preparation of novel crystalline liquid trans-4- (trans-5-Subst.-1,3-dithian-2-yDcyclohexancarbonsäureester.

Explanation of the essence of the invention

The object of the invention is a process for the preparation of novel crystalline liquid trans-4- (trans-5-substituted-1,3-dithian-2-yl) cyclohexanecarboxylic acid esters in good yield and high purity. It has been found that crystalline liquid trans-4- (trans-5-Subst.-1,3-dithian-2-yl) cyclohexanecarboxylic acid esters of the general formula can be prepared by adding 2-subst.-propane-1,3- dithiols to a boiling solution of trans ^ -formyl-cyclohexanecarboxylic, preferably -methyl or -äthylestern, and an acid catalyst such. For example, p-toluenesulfonic acid or boron trifluoride in a suitable solvent such. B. CHCl 3 or benzene, wherein the reaction water formed is distilled off simultaneously azeotropically. The separation of the pure trans isomer succeeds here by fractional crystallization from a solvent, preferably methanol. The cis-isomer enriched in the mother liquor can be equilibrated to the trans isomer by known methods. By this method, preference is given to obtaining simple alkyl esters, such as methyl or ethyl esters, which are reacted further in accordance with the reaction scheme indicated. The trans-4- (trans-5-Subst.-1, S-dithian-cycyclohexanecarboxylic acids obtained by alkaline hydrolysis are converted with appropriately substituted alcohols or phenols to the trans-4- (trans-5-Subst.-1,3- dithian-2-yl) cyclohexanecarboxylic esters, where in trans-4- (trans-5-substituted-1,3-dithian-2-ylcyclohexanecarboxylic acids directly, for example by means of carbodiimides, or after conversion into the acid chlorides according to known methods to be esterified

 The substances produced according to the invention are new and have pronounced crystalline-liquid properties.

synthetic scheme

/ COOEt COOEt 1

LiAlH

^0H

Oh ei

\

OTos

1. (H,

2. OH

3. Η ^β

V / VCOOEt

recryst.

SH

OHC

COOC ₂ H ₅

BF ₃ .Et ₂ O

CHC1 _{3 /} RT (equilibration)

Vs / ^ / ^C00Et

1. OH

2. H

^R -i ri Vcooh V / \ /

SOCI,

^C 6 ^H 6 Vs / \ - /

COCI

R'OH / pyridine

embodiments Example 1:

2-Subst.-1,3-di-p-toluenesulfonyloxypropanes 2

To a solution of 0.528 mol (105 g) of p-toluenesulfochloride in 150 ml of absolute pyridine at 0 ° C with stirring, a solution of O, 26mol 2-substituted propane-1,3-diol 1 in 90ml abs. Pyridine added dropwise. The resulting solution is stirred at ⁰ ° C. for 40 h and then poured onto a mixture of 750 h ice / 300 ml conc. Hydrochloric acid and 150 ml of water. The precipitated solid is taken up in CH ₂ Cl ₂ . This solution is washed with 200 ml of 10% hydrochloric acid and twice with 300 ml of water. After drying over Na ₂ SO ₄ , the solvent is distilled off and the residue is recrystallized from hexane / ethyl acetate.

R_pu f pu ncn _ / f ~ * \ \ pu ^

R Yield Fp

[% J [ ⁰ C]

C ₅ H ₁₁ 72 '60-61

C ₆ H ₁₃ 90 50-51

^ 6 ^ 13 ^ ~ \ Q / ^{86 69} ~ ⁷²

Example 2: 2-Subst.-1,3-dimercaptopropane 3

A solution of 0.1 mol of subst.-1,3-di-p-toluenesulfonylpropane and 0.22 mol (16.7 g) of thiourea in 100 ml of ethanol is heated to boiling for 6 hours. After cooling, the solvent is largely distilled off on a rotary evaporator and the residual thiuronium salt is refluxed with 120 ml of 5 N sodium hydroxide solution for 2 hours under a protective gas atmosphere. The cooled reaction mixture is acidified with 2N hydrochloric acid and extracted three times with ether. The combined ether extracts were dried over Na ₂ SO ₄ , the solvent was distilled off in vacuo and the residue was fractionated in vacuo.

R-CH (CH ₂ SH) ₂ R yield kp [%] [° C, mm Hg] C ₅ H ₁₁ 95 75 / 0.2 C ₆ H ₁₃ 96 84 / 0.25 ^C 6 ^H 13 ° - <5> - 89 180 / 0.1

Example 3:

Trans-4- (trans-5-n-hexyl-1,3-dithian-2-yl) cyclohexanecarboxylic acid ethyl ester 4 0.05 mol of 2-subst.-propane-1,3-dithil is slowly added with stirring and protective gas to a water separator Reflux solution of 0.055 mol (10.1 g) of methyltransylformhylcyclohexanecarboxylate and 100 mg of p-toluenesulfonic acid in 250 ml of benzene is added dropwise After the addition has ended, the mixture is heated for a further 20 minutes and the reaction mixture is then cooled to room temperature, with 100 ml of 5% NaNCO 3 ₃ solution and 100 ml of water and the solvent was distilled off on a rotary evaporator in vacuo.The residue is recrystallized from MeOH until the constancy of the transition temperatures.

Yield: 20% d. th

KS ₈ 134 I

The mother liquors obtained by recrystallization were combined, the solvent is distilled off on a rotary evaporator and the residue in 250 ml abs. CHCI ₃ dissolved. After addition of 2 ml of BF ₃ Et ₂ O 72h is allowed to stand at room temperature and worked up as above

 Repeated equilibration yields a total yield of about 80% of isomerically pure product.

Example 4:

trans ^ -ftrans-ö-n-hexyl-1S-dithiane ^ -yO-cyclohexanecarboxylic acids 5

0.2 mol (11.2 g) of KOH are dissolved in 10 ml of water and added to a solution of 0.035 mol (12.6 g) of trans-4- (trans-5-n-hexyl-1,3-dithian-2-yl) - cyclohexanecarboxylic acid ethyl ester in 200 ml of methanol. After boiling for 2 hours under reflux, the solvent is largely distilled off on a rotary evaporator. The residue is dissolved in 250 ml of water, acidified with 10% hydrochloric acid and the resulting precipitate is filtered off with suction and recrystallized from hexane / ethyl acetate.

Yield: 90% d. th

 K 220N230 I

Example 5:

Trans-4- (trans -5-n-hexyl-1,3-dithian-2-yl) cyclohexanecarboxylic acid (4-cyanophenyl) ester 6 0.01 mol (3.30 g) of trans-4- (trans-5-) n-hexyl-1,3-dithian-2-yl) -cyclohexanecarboxylic acid, 0.01 mol (1.19 g) of 4-cyanophenol, 100 mg of 4-dimethylaminopyridine and 0.011 mol (3.27 g) of CI-P-dimethylaminopropyU-S- Ethylcarbodiimidmethiodid are dissolved at room temperature with stirring in 50 ml of absolute methylene chloride and allowed to stand for 24 h at room temperature. For working up, it is diluted with 100 ml of methylene chloride, washed four times with 100 ml of water, once with 100 ml of 5% NaHCO 3 solution and again with 100 ml of water, dried over Na ₂ SO ₄ and the solvent on a rotary evaporator

distilled off. The residue is recrystallized from methanol. · -

Yield: 80% d. Th.

The transformation temperatures of this substance and other substances synthesized in analogy to this procedure are given in Tab. 1 and 2.

table

is

-C2H5 -C4H9

• 50

• 134

• 121.7

• 115.5

CH

1/8 -CH ₂ CH ₂ CN

• 60

• 55

• 60

• 85

• 122.5

• 120 • 118 • 120.5 • 125.5

table

S _B

is

2/1 2/2 2/3 2/4 2/5 2/6

OC ₄ H ₉ OC5H11 CN CH

CN

.COO - ^ - OC ₄ H ₉ H

H • 45 - - • 130 • 157 H • 70 - - • 186.5 • 191 H • 85 - - • 186 • 219 H' • 95 - - • 187 • 210.5 H • 130 - - - - • 228 CH ₃ • 100 - - • 117.5 • 174.3 H • 91 • 226 • 238 • 286 H • 102 • 174 • 179 • 315 H • 110.5 - - - - • 298 H • 109 • 276

Claims (1)

A process for the preparation of novel crystalline liquid trans-4- (trans-5-Subst-1, S-'dithian-2-yl) cyclohexanecarboxylic acid esters, characterized in that 2-subst-propane-1,3-dithiols to a boiling solution of trans ^ -Formylcyclohexancarbonsäureestern, preferably ethyl or methyl ester and an acidic catalyst such as. For example, p-toluenesulfonic acid or boron trifluoride in a suitable solvent such. B. CHCl ₃ or benzene with simultaneous azeotropic removal of the water of reaction, be added, wherein the trans-4- (trans-5-Subst-1,3-dithian-2-yl) cyclohexanecarboxylic acid ester by fractional crystallization from a solvent, preferably methanol are separated from the cis-isomers, which are also convertible by multiple equilibration in the trans isomers, then the resulting trans-4- (trans-5-Subst-1,3-dithian-2-yi) cyclohexanecarboxylic acid ester by means of aqueous Alkalis to give the trans-4- (trans-5-Subst-1,3-dithian-2-yl) cyclohexanecarboxylic and saponified after conversion into the acid chloride or directly with appropriately substituted alcohols or substituted phenols. Field of application of the invention The invention relates to a process for the preparation of novel crystalline liquid trans-4- (trans-5-Subst.-1,3-dithian-2-yDcyclohexancarbonsäureester the general formula: