GB2238309A

GB2238309A - Liquid crystalline phenyl-naphthalenes

Info

Publication number: GB2238309A
Application number: GB9024433A
Authority: GB
Inventors: George William Gray; David Lacey; Kenneth Johnson Toyne; Michael Hird; Damien Gerard Mcdonnell; Edward Peter Raynes
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1989-11-10
Filing date: 1990-11-09
Publication date: 1991-05-29
Also published as: GB8925414D0; GB9024433D0

Abstract

Novel phenyl-napthalenes having liquid crystalline properties are disclosed of general formula I: <IMAGE> wherein R1 is C1-15 alkyl or alkoxy or perfluoroalkyl or perfluoroalkoxy or CN; R2 is CN, halogen, C1-15 perfluoroalkyl or perfluoralkoxy, NCS, C1-15 alkyl or alkynl or alkoxy; m is 0, 1 or 2; provided that R1 and R2 are not both alkyl, alkoxy, perfluoroalkyl or perfluoroalkoxy unless m is 0.

Description

PHENYL-NAPHTHALENES HAVING LIQUID CRYSTALLIDE PROPERTIES This invention relates to novel phenylnaphthalenes having liquid crystalline properties and to their use in liquid crystal materials and devices.

Liquid crystal materials and devices exploit the electro-optical properties of nematic or cholesteric (N or N*), or smectic (S) in particular chiral smectic C (Sc*) or smectic A (SA) phases. The most common type of liquid crystal materials in use are those which show a nematic phase, and these are extensively used in for example watches, clocks, calculators, electronic displays etc.

Liquid crystal materials desirably are easy to prepare, show liquid crystal phases which persist over a wide temperature range which preferably includes room temperature, and useful physico-chemical properties such as birefringence. For some applications of liquid crystal materials a high birefringence is sought, e.g.

in the so-called "electrically controlled birefringence" (ECB) effect device (see, for example, N F Schieckel and K Fahrenschon Appl. Phys. Lett (1971), 19, 2912), in thin film transistors (TFT) or supertwist twisted nematic (STN) devices. It is rare for all the requisite desirable properties to be found in a single liquid crystalline compound, and generally liquid crystal materials consist of mixtures of component compounds.

Very many liquid crystalline compounds suitable for such uses are known and will be apparent to those skilled in the art.

Some investigations have been carried out of compounds containing a naphthyl group, for example Applicant's co-pending GB 8900871 (Applicant's Ref: PO743) describes a series of such compounds, as components of liquid crystal materials.

It is an object of this invention to provide novel phenyl-naphthalene compounds having liquid crystalline properties or being otherwise suitable for use as component compounds in liquid crystal materials.

According to this invention phenyl-naphthalenes of general formula I are provided

Formula I wherein R1 is C1 15 alkyl or alkoxy or perfluoroalkyl or perfluoro-alkoxy, or CN; R2 is CN, halogen, Cm 15 perfluoroalkyl or perfluoroalkoxy, NCS, C1 15 alkyl or alkynyl; m is 0, 1 or 2 provided that R1 and R2 are not both alkyl, alkoxy, perfluoroalkyl or perfluoroalkoxy unless m is 0.

The preferred embodiments of the invention discussed below are inter alia chosen with respect to ease of preparation and their liquid crystal properties, particularly with respect to suitability for use in high birefringence nematic liquid materials.

Preferably R1 and R2, if organic substituents, contain 1-8 carbon atoms. A preferred halogen for R2 is fluorine. A preferred perfluoroalkyl group is CF3. When m is 2 the two fluorines are preferably in the 2,3-substitution positions on the phenyl ring.

Preferably one of R1 and R2 is a non-polar group, such as alkyl, alkoxy or alkynyl and the other is polar, such as CN, halogen (e.g. fluorine), NCS or a CF3- terminated perfluoroalkyl or perfluoroalkoxy such as CF3 itself.

Preferred overall structures for the phenylnaphthalenes of formula I are listed below Table 1

where R is alkyl or alkoxy, especially alkoxy and R1 is alkyl.

Phenyl-naphthalenes of formula I may be prepared by generally applicable routes shown in Figures 1 to 3 of the accompanying drawings. 2-hydroxy-6bromonaphthalene and 2-aminonaphthalene are known. In these routes the reaction conditions of the individual steps are well known but the overall combination of steps to form the end product is novel. Compounds in which R2 is NCS, e.g. 1.6, are preferably prepared by initially incorporating an amino group into the molecule as R2, for example coupling the boronic acid with para-bromoaniline in step A3, and then converting this into an isothiocynanate. Ways of doing this will be apparent to those skilled in the art.

Routes D, E and F illustrate methods by means of which parabrominated intermediates for use in step A3 may be prepared.

This invention also provides a liquid crystal material being a mixture of at least two component compounds, at least one of which is a phenyl-naphthalene of formula I.

Phenyl-naphthalenes of formula I have nematic liquid crystalline properties. In particular, many have a high birefringence, making them suitable for applications in which this characteristic is required, as discussed above. Although some have rather high melting points, this can be in some cases be usefully reduced by introducing one or more lateral fluorosubstituents on the phenyl ring, e.g. as in 1.3, 1.5 and 1.8.

These compounds may be used as components of liquid crystal materials together with other known liquid crystalline compounds especially for example compounds of general formula II

Formula II where RA is Cl-10 n-alkyl or n-alkoxy. Other known compounds which may be usefully included as components of liquid crystal materials include those described, for example, in GB-1551043, GB-1556994, GB-1592147, GB-1587819, GB-1603076, GB-2011940, GB-2023136, GB-2027708, GB-2027027, GB-2058789, GB-2063250, GB-2071649, GB-2070594, GB-2071131, GB-2081707, GB-2079275, GB-2080820, GB-2089345, GB-A-8203798, EP-0060648, GB-2111974, US-4482472, GB-2118934, US-4506957, GB-2121406, EP-A-83303348.3, GB-2134110, EP-A-8430494.3, EP-A-84303240.0.

Generally, phenyl-naphthalenes of this invention may constitute 5-508 by weight of such a liquid crystal material.

Liquid crystal materials of the invention may be used in display devices of known construction and method of operation. Typically, an electrooptical display device will consist of two substrates between which a layer of the liquid crystal material may be sandwiched.

At least one of the substrates is optically transparent, and both have electrodes which are preferably made of a transparent material on their opposing faces. By applying an electric field across the layer of liquid crystal material via the electrodes an electrooptic effect is achieved which may be viewed directly or preferably through one or more polarising filters.

The invention will now be described by way of example only with reference to Figures 1 to 4 which show preparation routes to phenyl-naphthalenes of Formula I.

Example 1 Route A SteD Al A stirred solution of l-bromobutane (50 g, 0.36 mol) in acetone was added dropwise to a stirred ref fluxing mixture of 2-hydroxy-6-bromonaphthalene (40 g, 0.18 mol) and potassium carbonate (51 g, 0.37 mol) in acetone (300 ml). The stirred mixture was heated under reflux for 24 hr (i.e. until glc analysis revealed a complete reaction). The potassium carbonate was filtered off, water was added to the filtrate and the product was extracted into ether twice. The combined ethereal extracts were washed with water, 5% sodium hydroxide, water and dried. The solvent and the excess of l-bromobutane were removed in vacuo. The crude product was recrystallised from ethanol to yield an off-white powder.

Yield 32.3 g (64%) mp 52-530C.

SteP A2 n-Butyllithium (12.4 ml, 2.5 M in hexane, 0.031 mol) was added dropwise to a stirred cooled (-780C) solution of the product of step Al (8.602, 0.031 mol) in dry T}F (60 ml) under dry nitrogen. The reaction mixture was maintained under these conditions for 1.5 hrs and then a previously cooled solution of tri-isopropyl borate (12.0 g, 0.064 mol) in dry THF (50 ml) was added dropwise at -780C. Lithiation was monitored by glc analysis. The reaction mixture was allowed to warm to room temperature overnight and then stirred for one hour with 10% hydrochloric acid (30 ml).

The product was extracted into ether (twice), and the combined ethereal extracts were washed with water and dried (XgSO4). The solvent was removed in vacuo to yield a colourless solid.

Yield 8.5 g (100%) Step A3 A solution of para-bromobenzonitrile (1.25 g, 6.87 mmol) in ethanol (15 ml) was added to a stirred mixture of the product of step A2 (2.01 g, 8.24 mmol) and tetrakis-(triphenyl phosphine) palladium (0) (0.2917 g, 0.25 mmol) in benzene (30 ml) and 2M sodium carbonate (30 ml) at room temperature under dry nitrogen. The stirred mixture was heated under reflux (N1000C) for 4 hrs (i.e. until gle and tlc analysis revealed a complete reaction).The product was extracted into ether (twice) and the combined ethereal extracts were washed with brine and dried (XgSO4). The solvent was removed in vacuo and the residue was purified by column chromatography silica gel/petroleum fraction (bp 40-600C) - dichloromethane, 3:1] to give a colourless solid which was recrystallised from ethanol-ethyl acetate (8:1) to yield colourless crystals.

Yield 1.63 g (79%).

Example 2. Route E A solution of n-butyllithium (7.8 ml, 10.0 M in hexane, 0.078 mol) was added dropwise to a stirred, cooled (-5 to OOC) solution of pent-l-yne (5.28 g, 0.078 mol) in dry ThF (50 ml) under dry nitrogen. This mixture was stirred for 10 min and then a solution of dry zine chloride (10.80 g, 0.079 mol) in dry THF (100 ml) was added dropwise at -5 to 100C. The mixture was stirred at room temperature for 15 min and a solution of para-iodobromobenzene (5.28 g, 0.078 mol) in dry THF (100 ml) was added dropwise at -5 to OOC followed by the addition of tatrakis (triphenylphosphine)palladium (0) (2.80 g, 2.40 mmol). The mixture was stirred at room temperature overnight (glc analysis revealed a complete reaction) and poured into 10% hydrochloric acid.The product was extracted into ether (twice) and the combined etherea extracts were washed with aqueous sodium hydrogen carbonate and dried (MgSO4). The solvent was removed in vacuo to afford a liquid which was filtered through a short alumina column and eluted with dichloromethane. The solvent was removed in vacuo and the residue distilled to yield an oil.

Yield 14.20 g (82%) bp 130-1340C at 15 mm Hg.

Example 3, Stews B1 and B2 B1 A solution of N-phenyltriflamide (4.93 g, 0.0138 mol) in dry dichloromethane (50 ml) was added dropwise to a stirred cooled (-780C) solution of 2-hydroxy-6bromonaphthalene (2.80 g, 0.0126 mol) in dry dichloromethane (80 ml) and dry triethylamine (2.55 g, 0.25 mol) under dry nitrogen. The stirred mixture was allowed to warm to room temperature overnight (glc and tlc analysis revealed a complete reaction). The mixture was washed with aqueous sodium carbonate and the separated aqueous layer was washed with dichloromethane.

The combined organic extracts were washed with water and dried (NgSO4). The solvent was removed in vacuo and the residue was purified by column chromatography (silica gel/dichloromethane) to give an off-white solid.

yield 4.40 g (98%) mp 52-530C.

B2 Quantities: pent-l-yne (0.48 g, 7.14 mmol), n-butyllithium (2.90 ml, 2.5M in hexane, 7.25 mmol), zinc chloride (1.00 g, 7.35 mmol), the product of step B1 (2.14 g, 6.64 mmol), tetrakis(triphenylphosphine) palladium (0) (0.2621 g, 0.23 mmol), lithium chloride (0.5812 g, 14 mmol).

The experimental procedure was similar to that of route E described above, except that lithium choride was added with the tetrakis (triphenylphosphine)palladium (0) and the mixture was heated under reflux (oil bath at 1000C) for 22 hours (overnight for convenience; glc and tlc revealed a complete reaction). The crude product was purified by column chromatography (silica gel/ petroleum fraction (bp 40-600C) - dichloromethane, 10:1) to give a colourless solid which was recrystallised from ethanol - ethyl acetate (3:1).

The properties of the compound prepared in the examples above and of others prepared by analogous routes using different R2 groups are listed below (K solid crystal).

Table 2

R1 R2 m Liquid Crystal Transitions ( C) C4HgO CN 0 K 125.0 N 156.5 I C4H9O F 0 K 128.5 (N 112.9) I C4HgO F 1 K 72.0 (N 63.0) I C4H9O CF3 0 K 177.5 (N 95.0) I C4H9O CF3 1 K 73.5 SA 105.5 I Table 3

R2 m Liquid Crvstal Transitions ( C) OC4H9 0 K 98.5 167.5 I OC4H9 1 K 64 5 N 129.5 I C#C3H7 0 K 113.0 N 193.0 I

Claims

CLAIMS 1. Phenyl-naphthalenes of general formula I :

Formula I wherein R1 is C1 15 alkyl or alkoxy or perfluoroalkyl or perfluoro-alkoxy, or CN; R2 is CN, halogen, C1-15 perfluoroalkyl or perfluoroalkoxy, NCS, C1-15 alkyl or alkynyl; m is 0, 1 or 2 provided that R1 and R2 are not both alkyl, alkoxy, perfluoroalkyl or perfluoroalkoxy unless m is 0.
2. Phenyl-naphthalenes according to claim 1, having an overall structure

wherein R is alkyl or alkoxy.
3. Phenyl-naphthalenes according to claim 1, having an overall structure

wherein R is alkyl or alkoxy and n is 0 or 1.
4. Phenyl-naphthalenes according to claim 1, having an overall structure

wherein R is alkyl or alkoxy and n is 0 or 1.
5. Phenyl-naphthalenes according to claim 1, having an overall structure

wherein R is alkyl or alkoxy.
6. Phenyl-naphthalenes according to claim 1, having an overall structure

wherein R is alkyl or alkoxy and n is 0 or 1.
7. Phenyl-naphthalenes according to claim 1, having an overall structure

wherein R is alkyl.