CYANOHYDRIN DERIVATIVES AND THEIR USE IN LIQUID CRYSTAL MATERIALS AND DEVICES

Abstract: Novel cyanohydrin derivatives of general formula (I) wherein R<1> is hydrogen, alkyl, alkoxy, perfluoroalkyl or perfluoroalkoxy, R<2> is alkyl, r is 1 to 10, n and m are 0 or 1, provided if both n and m are 0 then X is (II) or (III), where (F) indicates one or more optional fluorines, p is 0 or 1, Z is a single bond if p is 0 and COO if p is 1; and if one or both of n or m are 1 then X is (IV), where each ring A, B and C is phenyl, fluoro- or chloro-phenyl, cyclohexyl, pyrimidyl, pyridyl, or dioxanyl, A, B and C are single bonds or linking groups, and (a + b + c) is 2 or 3. Liquid crystal materials containing these compounds are also described.

Description: CYAN0HY.BIN DERIVATIVES AND THESE USΞ IN LIQUID GPYΞTAL MATERIALS AND DEVICES. This invention relates to cyanohydrin derivatives and also o liquid crystal materials containing them. In particular the invention relates to chiral derivatives and ferroelectric smectic liquid crystal compositions containing them. Ferroelectric smectic liquid crystal materials are known, (eg N A Clark et al: Appl Phys Lett (1980) 36 899), and exploit the electro-optical properties of the ferroelectric chiral smectic phase. The chiral smectic C (abbreviated SΛ the asterisk denoting chiralty) is most used as it is the most fluid, but other chiral smectic phases eg I, F, J, K, G, H or X may also be used. Although some ferroelectric smectic liquid crystal materials are single compounds it is more usual for such a material to be a composition. Generally such a composition contains one or more compounds which either singly or together show an S phase (termed a smectic "host"), together with one or more chiral (ie optically active) compounds which are generally added to induce the smectic material to show a high spontaneous polarisation. Ps. The composition may also contain additives.. For example to broaden the Sc* range, to suppress undesirable phases, or optically active compounds to modify the helical pitch of the Sc* phase. Among the features sought in a good ferroelectric smectic liquid crystal material are low viscosity, fast switching speeds, a broad Sc* phase range, and a high spontaneous polarisation coefficient Ps and a long helical pitch. In view of the high cost of synthesis of optically pure compounds it is also desirable that the chiral compound is cheap. Optically active compounds used in ferroelectric smectic liquid crystal compositions generally consist.of a "core" consisting of a chain of linked cyclic groups, with an optically active group containing an asymmetric carbon atom at or near a terminal position of the chain. The core is selected from the reasonably well known combinations of cyclic groups which encourage the compound to be miscible with smectic liquid crystal phases. The goal of much research in ferroelectric smectic liquid crystal chemistry is to identify novel optically active groups which may be combined with such cores to form advantageous compounds. Many suitable optically active compounds are known. PCT/GB 87/00441 (Agents Ref P0383) and JPA-61-243055 describe compounds of structure where R is alkyl. These compounds show a high Ps. PCT/GB87/OOΨll has a publication date later than the priority date of this application. It is an object of the present invention to provide novel compounds which are suitable optically active constituents of ferroelectric liquid crystal compositions, and which have advantageous properties relative to known compounds. This invention provides compounds which are novel cyanohydrin derivatives having a general formula I: I wherein R is selected from hydrogen, C - C alkyl, alkoxy, per- fluoroalkyl and perfluoroalkoxy and may be straight chain or 2 branched chain; R is alkyl, which may be C - C straight chain, 1 o C - C branched chain or cyclic; r is an integer 1 to 10, n and m 1 15 are independently 0 or 1; with the provisos that: if both n and m are 0 then X is selected from: where the (F)'s indicate that X carries one or two fluorine sub- stituents in any one or two of the available lateral substitution positions on the indicated phenyl rings. is 0 or 1, Z is a single bond where p is 0 and COO when p is 1, and; if one or both of n or m are 1 then X is a group of general formula: -(-(T -Λ-)-(- B -B-)-( - G)-)- a Λ — " b — c where each ring A, B and C is independently selected from phenyl, fluoro or chloro substituted phenyl, cyclohexyl, pyrimidyl, pyridyl or dioxanyl, each link A, B and C is indenpendently a single bond, COO, 00C, CH CH , CH=N, N=CH, CH 0, OCH or 0, and each of a, b and c is 0 or 1 provided (a + b + c) is 2 or 3. The structural preferencies expressed below are on the basis of ease of preparation and/or advantage in liquid crystal compo- sitions, particularly of the ferroelectic type. Preferred compounds of formula I therefore have a formula II: R 1 -(-GK=GH-(-GH„- ' ) -C-) -X-(-CGH -) -GCOCxϊ-R" II -r n 2 J ~ -^ wherein Rl is selected from C - C alkyl or alkoxy; R -, r, n and m are as defined in formula I, with the provisos that: if both n and are O then X is selected from: where p and Z and their relationship are as defined in formula I and (F) indicates that the biphenyl system carries one or two fluorine substituents on any one or two of the available sub¬ stitutions positions of the biphenyl system, and if one or both of n or m are.1 then X is a group of general formula: wherseach ring A, B and C is indenpendently selected from phenyl, fluoro or chloro subsititued phenyl and trans-cyclohexane. c is 0 or 1, B is COO or a single bond, being a single bond if c is O. if n and m are not both O, then preferably one rather than both of n or i is 1. In formula II, X is preferably biphenyl or laterally monofluorosubstituted biphenyl. Particularly preferred compounds of formula II are those of formula IIA, ie a subclass of the case where n and m are both O. - 1 2 where R (F), Z, p and R , and their relationship are as defined in formula II above. Preferably in formula IIA there is one sub- stituent (F), or two in the 2,3 or 2' ,3' positions on the " biphenyl. Some preferred structural types encompassed by formula IIA are those listed in table 1 below: Table 1 F CN R- L -<O>-(θ>-GC0CH-I. IIA1 CN R 1 - θ - θ -C00GH-E 2 IIA2 CII I R 1 - θ -rø -GCCGH-R 2 IIΛ' Table 1 (Cont) CN B 1 -®-^ 1 ? COOCH-Γ. IIA'-. of these, formulae IIAl, 2, 3 ^, 9 are particularly preferred. Another preferred class of compounds of formula II are those of formula IIB: wherein R1, r, B, c and R2 are as defined in formula II, (F) indicates that the relevant phenyl ring may carry a fluorine sub- stituent, is fluorine or chlorine and d is O or 1. Preferably r in formula IIB is 1 to 6, more preferably 1 to 4. Some preferred structural types encompassed by formula IIB are those listed in Table 2 below where R -CH=CH-(CH 2 )-O is abbreviated to RB: Table 2 ' --@- - < 2 ~ C :l-? 2 1131 Table 2 (Contd) IIBIO Of these, formulae IIB 1, 2 3, 4 and 5 are particularly pref- ferred. Another preferred class of compounds of formula II are those of general formula IIC, another subclass of formula II where both n and m are O. wherein R 1, B, C and R2 are as defined inforumla II, (F) indicates that the relevant phenyl ring may carry afluorine substituent, Q is fluorine or chlorine and d is 0 or 1. Some preferred structural types encompassed by formula IIC are those listed in Table 3 below: Table 3 Table 3 (Contd) CN F1 -^^^^^- G OO-^^-OCH 2 C OCH-R 2 HCβ F CN RR 1 --^^U -^OK-^^--0OCCHH 2 ^CC0O0OCCHH--RR ∑2 IIC9 Of these, forumlae II Cl, 2, 3, 4 and 5 are particularly preferred. A fourth class of preferred compounds of formula II are those of formula IID:- CN R1 ©^_COOCH-R 2 IID & where R 1 and 2 are as defined in formula II above. In all the formulae listed above the following preferences apply. R is preferably n-alkyl or n-alkoxy containing 3 to 11 carbon atoms, especially 5 to 9 carbon atoms. R 2 is preferably C^ - C ς n-alkyl especially methyl, cyclohexyl, or in particular a branched or asymmetrically substituted alkyl group R 3 of formula: SUBSTITUTESHEET, • x e ÷ 1 ( —~ " "* —-- ~ " .-<!r•? R- ~ ~ - ■ " d 2-r where w is 0 or an integer 1 to 5, and each of x and y are independently 1 to 6. Preferably is 0, and preferably at least 3 one of x and y is 1. R may be optically active or in a racemic mixture. In the above formulae, the carbon atom inidcated by an asterisk in formula I may be present in an optically active form or as a racemic mixture. 3 Preferred structures for R are listed blow in table 4, the most preferred being underlined. Table 4 CH 2 CH(CH 3 ) 2 CH 2 CH(CH 3 )C 2 H5 CH 2 CH(CH 3 )C 3 H 7 CH 2 CH(CH 3 )C4H9 CH 2 CH(CH 3 )C 5 H 11 CH 2 CH(CH 3 )C 6 H 13 CH 2 CH(CH 3 )C 2 H 15 CH 2 CH(CH 3 )C 8 H 17 CH2CH(CH3)C9H ig The invention also includes the use of compounds of formula I in liquid crystal compositions, and a liquid crystal composition which includes one or more compounds of formula I. The liquid crystal composition is preferably a smectic C (S ) liquid crystal composition, especially a ferroelectric chiral S composition. Preferred com- pounds of formula I for use in such compositions are as discussed above. Compounds of formula IIA in an optically active form, preferably those of formulae IIAl, 2, 3 and 4, and especially those of formula IIAl where R is n-alkoxy are particularly useful components of ferroelectric smectic liquid crystal compoistions. they generally have lower meltingpoints, igher solubilities in SQ materials, and when included in such a composition generally lead to a higher spontaneous polarisation Ps, than their unfluorinated counterparts eg as described in the cited prior art. These are useful and un¬ expected advantages. Compounds of formulae IIB, IIC and IID are also useful components of ferroelectric smectic liquid crystal compositions. One use to which they may be put is that of "pitch compensators" as defined below with compounds of formula IIA. A ferroelectic smectic liquid crystal composition of this in- vention as well as one or more compounds of formula I also contains one or more "host" compounds which either separately or together show an phase. Many such host compounds are known. Preferred host compounds are the known compounds of formula III: where Ra and R are independently C - C alkyl or alkoxy and (F) indicates that the biphenyl system may carry a lateral fluorine sub¬ stituent. Preferred compounds of formula III are those of forumula I IA below, ie those described in PCT/GB86/0040: -©-^-OO-^-.R, III Other preferred hoεt compounds are the known fluoro- and difluoro- terphenyls of general formula IV *+@-@-@-K IV where n is 1 or 2 and Ra and Rb are independently C - C alkyl or alkoxy. Preferred terphenyls of foruma IV are those described in EPA 8430494.3 of formula IV A: and those described in GB-A-8806220 of formula IV B: Preferably both Ra and Rb in formulae III and IV are n-alkyl or n-alkoxy. Other host compounds include cyanocyclohexanes of formula V: and phenyl pyrimidines of forumula VI: n- where Re, Re and Rf are independently C_ - C alkyl or alkoxy and Rd is n-alkyl. As well as containing one or more host compounds, the ferro¬ electric smectic liquid crystal compoisiton of this invention may also contain additives. These may for example be addivites which broaden the temeprature range over which the Sc phase persists, eg known compounds of formula VII: where Ra and Rb are independently C to C alkyl or alkoxy and (F) indicates a fluorosubstituent may be present. Additives of formula VII are particularly useful when the host is or includes compounds of formula III or III A. useful additives when the host is a terphenyl of formula IV, IVA, or VB are the cyano-terphenyls of general formula VIII: where n is 0 or 1 and Ra and Rb are independently C - C n-alkyl or n-alkoxy. Compounds of formula VIII are described in PCT/GB88/ Preferred additives of formula VIII have a formula VIII A: and are useful in suppressing S phases, s As well as containing these additives the ferroelectric smectic liquid crystal composition of this invention may also contain additives which are "pitch compensators" if the compound of formula I is in an optically active form. Pitch compensators are optically active compounds which have a twisting effect on the S phase which is of opposite handedness to that of the optically active compound of formula I. Some examples of pitch compensating additives are the compounds described in PCT/GB87/00223, eg IX: where Ra and Rb are independently C - C n-alkyl or n-alkoxy. If at least one of the optically active compounds of formula I is a compound of formula IIA, then pitch compensating additives may be compounds of formula IIB, IIC or IID. 5 In an alternative and preferred method of pitch compensation, two or more compounds each of any one of formulae IIA, IIB, IIC or IID, preferably of formula IIA, having twisting effects of opposite handedness may be used. For example two compounds of the same formula IIA but having the carbon atom indicated by * in formula I 10 in mirror image configurations may be used. By using pitch compensation the helical pitch of the ferro¬ electric smectic liquid crystal phase may be adjusted to provide a long pitch. The ferroelectric liquid crystal composition of this invention 15 typically but not exclusively has the following composition, expressed in weight percentages. Host compound(s) 30-99 preferably 50 - 90 Additive(s) 0-30 preferably 0 - 20 Compound(s) of formula I 5-50 preferably 5 - 30 20 Total 100 Such a ferroelectric smectic liquid crystal composition may be used in any of the known types of liquid crystal device suitable for such a composition, for example the "Clark-Lagerwall Device" described in Appl Phys Lett (1980), 36, 899. The physics of this 25 device and methods of constructing and using one are well known. Methods for preparation of compounds of formula I will now be described. Compounds of formula IIA may be prepared by a number of synthetic routes, but it is prefered to start from the acid X: Such acids may be commercially available, or else they may be prepared by for example routes Al to A^- shown in Fig 1 starting ~ ~ from known compounds, yielding the acids XI, X2, X3 and X^: The steps in routes Al, A2, A3 and A are: Steps All, A22 THF solvent, Mg, triisopropyl borate Steps A12, A23 Ethanol solvent, palladium (triphenylphosphine): A33 toluene, methyl 4-bromoacetate, 2M sodium carbonate. Steps A13, A24, Hydrolysis, ethanol sodium hydroxide: A34 H 2 S0 4' Step A21 1-bromoalkaπe, acetone,potassium carbonate. Step A32 Diazotisation, KCN Step AΨl butyl lithium / -70°C / B(0CH ) reacted with the lithium Grignard reagent. •Step A 2 Hyirogen Peroxide Step A'+3 RBr / butanone / potassium carbonate / reflux Step A as step A4l. Step A-4-5 palladium (triphenylphosphine) / toluene/ sodium carbonate / methyl- -bromobenzoate. Step A-46 potassium hy-iroxide/ IMS / reflux 2 hours. Compounds of formula IIB may be prepared by a number of synthetic routes, but it is preferred to start from the acid XI: which may be prepared by route B shown in figure 2. This route is of general applicability for use with any appropriate hydroxy-ester. In route B the steps are as follows:- Bl Bromoalkene, butanone solvent, K CO . B2 Potassium hydroxide, water/methylated spirit. Compounds of formula IIC may be prepared by a number of syn¬ thetic routes, but it is preferred to start from the acid XII: which may be prepared by route C shown in figure 3. This route is of general applicability to any phenol or alcohol. In route C the steps are as follows: Route C Cl Ethylbromoacetate, potassium carbonate, butanone solvent. C2 KOH, water, 2-methoxyethanol, ethanol. Compounds of formula IID may be prepared using the known naphthoic acids. These acids may then be esterified with an appropriately pro¬ tected alpha-hydroxy acid, deprotected and converted into the nitrile. Suitable routes are routes E, F and G in Figs 5, 6 and 7. Many alpha-hydroxy carboxylic acids H0-CH(R )C00H for use in these routes are commercially available, eg lactic acid and mandelic acid. Alter¬ natively one may start from an alpha amino acid such as valine as shown in Fig 4route D using the following steps: Dl Sodium Nitrite, H SO . D2 (a) K CO , ethanol-water 9:1 pH7 (b) benzyl bromide, DMF The individual steps of routes 5, 6 and 7 are as follows: Route E El As step D2 E2 N,N-dicyclohexyl carbodiimide (DCC), 4-(N-pyrrolidino)- pyridine (N-PPy) CH-Cl E3 5% Pd/C, hydrogen, ethanol E4 (a) oxalyl chloride, benzene, DMF (b) aqueous ammonia, diglyme Ξ5 S0C1 , DMF Route F Fl ( .) ethyl acetate, hydrogen chloride F2 KOH, ethanol, water F3 as step D2 iέ Route F (Contd ) F4 oxalic acid, 90% aqueous ethanol F5 as step E2 F6 a series of steps analogous to steps E3 - E5 Route G Gl hydrogen, 5% Rh/Al 0 , methanol (starting compound: mandelic acid) G2 as step D2 using methanol solvent G3 DCC, N-PPy, CH Cl G4 hydrogen, 5% Pd -C, ethanol G5- as steps E4 and Ξ5 G6 Related routes may be used to prepare other compounds of formula IIA. Inroutes E, F and G, Y represents the particular group between 1 R and COO in formula I, for example Y may be: -<o o in the preferred formula II compounds discussed above. The invention will now be described by way of example only, with reference to Figs 1 - 7 which show preparative routes for compounds of formula I, and Fig 8 which shows a cross sectional view through a liquid crystal display device. Abbreviations C = solid crystal N = nematic liquid crystal S_ = smectic C S = smectic A A I = isotropic liquid All temperatures (melting point, boiling point, liquid crystal transitions, eg C-I, are in degrees centigrade). Example 1: RoutesAl and E to prepare: Steυs All - A13 3'-fluoro-4'-octoxybiphenyl-4-carboxylic acid was first prepared by the following method: 4-Bromo-2-fluσrooctoxybenzene (95g) (made by standard bromination of 2-fluorooctoxybenzene) was dissolved in dry tetrahydrofuran (250ml) and slowly added to a mixture of magnexium turnings " (8.5g) and tetrahydrofuran (50ml) containing a crystal of iodine. The Gagnard reaction was initiated by heating the solution. After the addition of bromide solution the mixture was stirred and refluxed under nitrogen for one hour. this solution was then transferred via a flexi-needle into a solution of triiso- propylborate (123g) in tetrahydrofuran (10ml) at -70°C in a nitrogen atmosphere over 30 minutes. The mixture was then allowed to warm up to room temperature over 3 hrs. 10% HC was added to the mixture and the organic layer separated, washed with brine, dried and solvent removed. The crude solid was dried in vacuo at 20°C. Yield 80. g. The product (32.2g) in methylated spirits (50ml) was added to a mixture of palladium tetra (triphenylphosphine) (0.6g), tolvene (200ml), methyl 4-bromobenzoate (21.5g) and a 2M solution of sodium carbonate (100ml). The mixture was heated under reflux and stirred vigorously for 16 hrs. After cooling, the reaction ITUTE SHEET 13 mixture was poured into water and the organic layer separated. The aqueous layer was extracted twice with toluene and the combined organic layers washed once with water. The solvent was removed, and the dark brown solid chromatographed on alumina (lOOg) using a mixture of dichloromethane and petroleum ether. Yield 46.9g. After crystallisation from methylated spirits the yield was 24.4g : mp 90°C. HPLC 99.9%. Step £L S-(+)- lactic acid (200g) was dissolved in 90% aqueous methanol (2000 ml) and treated with 20% aqueous sodium carbonate until the pH was 7. The solvent was removed at 50°C under vaccuum and then azeotropically removed using dichloromethane (600 ml). The lactic acid potassium salt was dissolved in dry dimethyl formanide (12 ml) and benzyl bromide (278 ml) added over 30 minutes. This solution was stirred for 16 hours. Solvent was removed under vacuum at 40-50°C, water (600 ml) was added and the product was extracted into ether. After drying over sodium sulphate the e ther layer was distilled to yield a colourless oil bp 88-90°C at 0.5 mm Hg/Yield 279g, 70%, glc 99.2%. Step -≤- '2 The product from Step Al? (lOg) was stirred for 16 hrs with dry tolune (120 ml), oxalyl chloride (12.4g) and ten drops of dry DMF. The toluene was distilled off and the acid chloride and redissolved in toluene (40 mis) and added to the product from Step El '4.41g) a pyridine (20 mis). The mixture was stirred for 30 minutes at 20°C then heated under reflux for 3 hours. After cooling the solution was carefully neutralised with dilute hydrochloric acid, the organic layer was removed and washed with sodium bicarbonate solution, then water. After drying, the organic layer was chromatσgraphed on aluminium. Yield 65% after crystallisation from IMS. Step E? The product from Step E2 - (8.2g) was, issolved in ethyl acetate (65 is). 5* Pd on carbon (lg) was added and the mixture stirred under a hydrogen atmosphere overnight. The catalyst was filtered off and the solution evaporated and the white solid dried under vacuum. Yield 98%. Step Ξ The product from Step ~ \ ~ (5g) was stirred at 20°C with tolvene (100 ml), DMF (10 drops) and oxalyl chloride (2.87g) for 3hrs. The solvents were removed and the acid chloride dissolved in day dichloromethane (100 mis). To this solution was added a mixture of dichloromethane (100 ml) and cone ammonia solution (1.5 ml) over about 10 minutes. After a further 10 minutes stirring at 20°C r water (200 mis) was added and the solution separated. The organic layer yielded 4g of a white solid. This was dried at 40°C under vacuum and used in the next step. ste P S5 to DMF (8 ml) was added ι thionyl chloride (10.7g), and the product from Step Ξ-4- (4g), dissolved in dimethylfσrmamide (40 ml), was added to the cooled thionyl chloride solution. This mixture was stirred at 10.75°C for 2 hours and then ice/water (200 g) was added. The product was isolated by extraction into ether followed by chromatography on silica gel. After crystallation from heptane a white solid was obtained. Yield 2.8g - The product showed C-I transition at 56°C Mixture Example 1 A ferroelectric smectic liquid crystal mixture was prepared which consisted of a 10 weight % solution of the product of Step E$ in: ght re SUBSTITUTE SHEET This composition had the following properties: (1) Liquid crystal transitions: Sc at room temperature and below Sc-S A 83°C S A -N 109.6°C N-I 137.140°C (2) Ferroelectric properties: Tilt (") 21.5 22.0 The extrapolated Ps of the cyanohydrin compound, deduced from this composition, 20°C below the S G - S A transition was 1 0 nCc . Exam le 2 was prepared using the acid prepared in steps All - A13 of Example 1 above, and route D. The experimental conditions for route D were the same as used for steps 4(1) and 4(2) of Example 5 on page 31 of WO 87/07890. C-I = 50°C. The extrapolated Ps value of a 10 wt % solution in the same liquid crystal host as used in mixture Example 1 was 250nCcm 20°C below the Sc-S transition temperature. In a Ά host mixture consisting of a 1:1:1:1 ratio of terphenyls of formula where R was C^, ^H^ c^.. and C^H^ (all n-) the extrapolate d Ps was 236 nCcm- 1 . Using analogous methods, compounds of analogous structure but where R 3 was CI^CIHCH^, CH(CH 2 )C 3 H-. and CH^CH, starting froπ L-leucine, L-isoleucine, and L-norleucine were prepared. SUBSTITUTE SHEET The following results compare the solubility of the compounds of examples 1 an 2 in the host mixture used in mixture example 1, their melting points, and their extrapolated Ps values at 20 C below S CJ - SA. , with the corresponding values for their unfluorinated analogues. Compound ext. Fs 190 CN 10 n-C 8 H 1? 0-^)-^-C00CHGH^ CN n-G 9 H 19 0-Jθ -<g -C00CHGH 170 20 Two more mixture examples are given below, using compounds o^ examples**.1 an 1 2, an^ taking advantage of their high solubility: asymmetric centres (• • #) in these two were o: r opposite con igurations. 5 This mixture showed: S G -S A 23°C, S -N 73°C. N-I 83.6°C Ps at 18°C = ^6 nGcm -1 .. .. 3°C = 66 SUBSTITUTE S ≤ΞT >.o ' .O o v-π o £ H -Λ O ON O Ω Example 3 Routes 3 and E Preparation of : Step Bl . Methyl 4-hydroxybiphenyl-4-carboxylate (17g), bromopentene (12.7g) butanone (200ml) and anhydrous potassium carbonate (22g) were stirred and heated under reflux for 16 hrs. The colled solution was filtered, and the solid washed with acetone (1001 1). The combined filtrates were evaporated to dryness, taken up in dichloromethane (200 ml), washed with water (2 x 50 1), dried over sodium sulphate and evaporated to dryness. The solid was crystallised from methylated spirits. Yield 20g. Step B2 The product from Step SI (I9.5g) was stirred and heated under reflux for 2 hours with potasium hydroxide (8.4g), water (30 ml) and methylated spirits (100 ml). The solution was pouredintowater (100mis) and acidified wity cone Hce. The solid was filtered off, washed with water and dried in vacuo. After crystallisation from acetic acid a yield of 15g was found. HPLC 99.6%. Step El S-(+)- lactic acid (200g) was dissolved in 90% aqueous methanol (2000 ml) and treated with 20% aqueous sodium carbonate until the pH was 7. The solvent was removed at 50°C under vaccuum and then azeotropically removed using dichloromethane (600 ml). The lactic acid potassium salt was dissolved in dry dimethyl formanide (12 ml) and benzyl bromide (278 ml) added over 30 minutes. This solution was stirred for 16 hours. Solvent was removed under vacuum at 40-50°C, water (600 ml) was added and the product was extracted into ether. After drying over sodium sulphate the e ther layer was distilled to yield a colourless oil bp 88-90°C at 0.5 m Hg/Yield 279g, 70%, glc 99.2%. Step r'- The product from Step B2 dOg) was stirred for 16 hrs with dry tolune (120 ml), oxalyl chloride (12.4g) and ten drops of dry DMF. The toluene was distilled off and the acid chloride and redissolved in toluene (40 mis) and added to the product from Step Ξl (4.41g) a pyridine (20 mis). The mixture was stirred for 30 minutes at 20°C then heated under reflux for 3 hours. After cooling the solution was carefully neutralised with dilute hydrochloric acid, the organic layer was removed and washed with sodium bicarbonate solution, then water. After drying, the organic layer was chromatographed on aluminium. Yield 65% after crystallisation from IMS. Step -^3 The product from Step E2 (8.2g) was dissolved in ethyl acetate (65 is). 5% Pd on carbon (lg) was added and the mixture stirred under a hydrogen atmosphere overnight. The catalyst was filtered off and the solution evaporated and the white solid dried under vacuum. Yield 98%. Step The product from Step E3 (5g) was stirred at 20°C with tolvene (100 ml), DMF (10 drops) and oxalyl chloride (2.87g) for 3hrs. The solvents were removed and the acid chloride dissolved in day dichloromethane (100 mis). To this solution was added a mixture of dichloromethane (100 ml) and cone ammonia solution (1.5 ml) over about 10 minutes. After a further 10 minutes stirring at 20°C, water (200 mis) was added and the solution separated. The organic layer yielded 4g of a white solid. This was dried at 40°C under vacuum and used in the next step. DMF (8 ml) was added* thionyl chloride (10.7g), and the product from Step EU- " (4g), dissolved in dimethylformamide (40 ml), was added to the cooled thionyl chloride solution. This mixture was stirred at 10.75°C for 2 hours and then ice/water (200 g) was added. The product was isolated by extraction into ether followed by chromatography on silica gel. After crystallation from heptane a white solid was obtained. Yield 2.8g. Mixture Example ? A ferroelectric smectic liquid crystal mixture was prepared which consisted of a 10 weight solution of the product of Step in: ~ 5 This composition had the following properties: (1) Liquid crystal transitions: Sc at room temperature and below Sc-S A 83°C S A -N 109.6°C N-I 137.140°C (2) Ferroelectric properties: Example ~~ Preparation of Using Routes ~ and E Step Cl 4-nonyloxy-4-biphenol (59.4g), ethyl bromoacetate (26ml), potassium carbonate (40g) and butanone (960ml) were stirred and heated under reflux for 28 hrs. The hot solution was filtered and allowed to cool with stirring. The product was filtered off under vacuum and dried. Yield 53.7g? 71.6%. Hplc 99.3%. Step 02 The product from Step Cl (53.7g) was heated on a steam bath for 5 hrs with potassium hydroxide (20g), water (60ml) and 2-methoxyethanol (800ml) . About 400ml of industrial methylated spirits was added to reduce foaming. After cooling, cone.HCL was added to adjust the mixture to pHl. The mixture was then stirred and heated for 1 hour. After cooling the solid was filtered and dried at 40°C under vacuum. Yield 43g. Step Ξl S-(+)-Lactic acid (200g) was dissolved in 90% aq. methanol (2000 ml) and treated with 20%aq. potassium carbonate until the pH was 7. The solvent was removed at 50°C under vacuum and then azeotropically removed using dichloromethane (600ml). The lactic acid potassium salt was dissolved in dry dimethylformanide (1200ml) and benzyl bromide (278ml) added over 30 minutes, this solution was stirred for 16 hrs. Solvent was removed under vacuum at 40-50°C, water (600ml) was added and the product extracted into ether. After drying over sodium sulphate the ether layer was distilled to yield a colourless oil hp 88-90°C at 0.5 mmHg. Yield 279g; 70%, glc 99.2% _ ^ ~ ^ " ' - ~ 12.9° Step S3 The product from Step C2 (lOg) was stirred for 16 hrs with dry toluene (120ml), oxalyl chloride (12.4g) and tem drops of dry dimethylformamide. The toluene was distilled off and the acid chloride redissolved in toluene (40mls) and added to the product from Step 31 (4.41g) on pyridine (20mls). The mixture was stirred for 30 minutes at 20°C then heated under reflux for 3 hours. After cooling the solution was carefully neutralised with dilute hydrochloric acid, the organic layer was ; removed and washed with sodium bicarbonate solution, then water. After drying, the organic layer was chromatographed on alumina. Yield 8.5g; 65%, after crystallisation from IMS. Step ~ ~ . The product from Step Ξ2 (8.2g) was dissolved in ethyl 10 acetate (65mls). 5% Pd on carbon (lg) was added and the mixture stirred under a hydrogen armosphere overnight. The catalyst was filtered off and the solution evaporated and the white solid dried under vacuum. Yield 6.7g; 98% mpt 150°C. Step TT-i- The product from Step E? (5g) was stirred at 20°C with Toluene (100ml), dimethylformamide (10 drops) and oxalyl chloride (2.87g) for 3 hrs. The solvents were removed and the acid chloride dissolved dry dichloromethane (100 ml). To thϊs solution was 20 added a mixture of dichloromethane (100ml) and con ammonia solution (1.5ml) over about 10 minutes. After a further 10 minutes stirring at 20°C, water (200 mis) was added and the solution separated. The organic layer yielded 4g of a white solid. This was dried at 40°C under vacuum and used in the next step. 2 ~ Step 35 Dimethylfo-rmamide (8mls) was added to thionyl chloride (10.7g), and the product from Step 34, dissolved in dimethylformamide (40ml), was added to the cooled thioαyl chloride solution. This mixture was stirred at 10-75°C for 2 hours and then ice/water (200g) was added. The product was isolated by extraction into ether followed by chromatography on silica gel. After crystallisation from heptane a white solid was obtained. Yield 2.8g, Mpt 108-110°C. ? ς 23 T.ixture Tic_.in.pl e 90 wt i c. H l9 G^ (^-(^- 0CH 2 G0GGHGE 10 wt % I CN This material had the following properties: Room temperature a N-I Example 5 j-re " ara ion of: usinp. route Step El c S-(+)-Latic acid (200g) was dissolved in 90% aqueous methanol (2 L) and treated with 20% aqueous potassium carbonate until the pH was 7. The solvent was removed at 50°C under vacuum and then azeotropically removed using dichloromethane (600 ml). The lactic acid potassium salt 5 was dissolved in dry dimethylformanide (1200 ml) and benzyl bromide (278 ml) added over 30 minutes. This solution was stirred for 16 hours. Solvent was removed under vacuum at 40-50°C, water (600 ml) was added and the product extracted with ether. After drying over sodium sulphate the ether layer was distilled to yield a colourless oil bp 88-90°C at 10 0.5 mm Hg. Yield 279g, 70%. glc 99.2, [oU ^ ' = ~ 12.9°. St p_ E2 6-Octoxy-2-Naphthoic acid (15g) [prepared by standard methods] was condensed with the product from Step El (8.33g) by dissolving both compounds in dichloromethane (300 ml) and adding trifluoroacetic anhydride 15 (10.7g). The mixture was stirred eX 20°C for 3 hrs, poured into water and the organic layer washed with dilute sodium bicarbonate solution until neutral. The organic layer was dried on sodium sulphate and purified by column chromatography on alumina. After crystallisation from petroleum spirit (hp 40-60°C) a white solid was obtained. Yield 20 8.5g; 38%. Step El The product of step E2 (8.2g) was dissolved in ethyl acetate (65ml) 5% Pd on carbon (lg) was added and the mixture stirred under a hydrogen atmosphere overnight. The catalyst was filtered off and the 25 solution evaporated and the white solid product dried under vacuum. Yield 95% after recrystallisation from petroleum spirit (bp 80-100°&C) Step & The product from Step S3 (6g) was dissolved in toluene (80ml), oxalyl chloride (3.85g) and dimethylformanide (6 drops) by stirring the ^0 mixture at 20°C for 3 hrs. the excess oxalyl chloride and toluene were removed under reduced pressure and the solid was dissolved in diglyme (45ml) and added dropwise to a stirred solution of 0.880 ammonia (50ml). After 30 min the mixture was diluted with water (180ml) and filtered. The solid was washed with water and dried at 40°C under vacuum. ~ 5 Yield 5.9g; 98%. Step S The product from Step E-Ψ (5.8g) was dissolved in dimethylformanide (20ml) and added dropwise to a vigorously stirred solution of thionyl chloride (17.5g) [previously redistilled] and dimethylformanide (60ml). After 2 hrs the mexture was poured into white/ice (200ml) and extracted with ether (2 x 150 ml) . The combined ether extracts were washed with sodium bicarbonate, water and then dried over sodium sulphate. After remobal of solvents the product was chromatographed on silica gel and recaptallised from heptane. Yield 3.0g; 55%. Mp 47°C. 10 Mixture Exaϋrele 5 The properties of this mixture were: Boom temp , and below ° , 10.7°G N-I 2 ~ ^■0 ~ \ °.l Example 6 was prepared using the acid prepared in steps A11-A13 of Example 1 above, and route G. The experimental conditions for route G were the same as used for steps 3(1) - 3(6) of Example 3 on pages 23-25 of WO 87/07890. Example 7 was prepared as follows; Step A21 n-C 6 ._ 13 C ^- r A solution of 1-bromohexane (9.33g) in acetone (20 ml) was added dropwise toa stirred mixture of 4-bromo-3-flurophenol (9.00g) and potassium carbonate (13.5g) in acetone (75 ml) at room temperature. The stirred mixture was heated under reflux for 21 hr (ie until glc analysis revealed a complete reaction). The product was extracted into ether twice, and the combined ether extracts were washed with water, 10% sodium hydroxide, water and dried (Mg S04). The solvent was removed under vacuo and the residue was distilled (bp 100-105°C at 0.1mm Hg) to yield a colourless liquid (12.7g, 98%). Step A22 5 A solution of n-butyllithium (10.0M in hexane, 3.30 ml) was added dropwise to a stirred colled (-78°C) solution of A21(9.0g) in dry THF (70 ml) under dry N . The stirred mixture was maintained under these conditions for 2.5 hr and then a colled solution of tri- isopropyl borate (11.28g) in dry THF (50 ml) was added dropwise at 10 -78°C. The stirred mixture was allowed to warm to room temperature overnight and then stirred for 1 hr at room temperature with 10% HC (50 ml). The product was extracted into ether twice and the combined ethereal extracts were washed with water and dried (Mg SO.). The solvent was removed in vacuo to afford an off-white solid ~ 5 (7.3g, 99%). Steps A23 and A24 These were performed using reaction conditions identical to those of Steps A12 and A13 of Example 1. The product was obtained as white crystals in a similar yield to that obtained in Example 1. 2.0, Using the acid produced in this way, and route E following the producedure as outlined in Example 1, the product cyanohydrin was obtained. Step A31 N-Bromosuccinimide (160.4 g, 0.90 mol) was added in small portions to a stirred, cooled solution of 2-fluroaniline (100.0 g, 0.90 mol) >0 - ~~ in dry dichloromethane (400 ml). The stirred mixture was allowed to warm to 0°C over 45 min, washed with water and dried (MgSO ) . The solvent was removed in vacuo to yield a red solid (180 g) which was steam distilled to give a colourless solid. Step A32 Concentrated sulphuric acid (60 ml) was added dropwise to a stirred mixture of the product of Step A31 (75.0 g, 0.90 mol), water (150 ml) and glacial acetic acid (185 ml). The clear solution was cooled to -5°C (an emulsion formed) and a solution of sodium nitrite (30.0 g, 0.44 mol) in water (100 ml) was added dropwise; the stirred mixture was maintained at -5°C for 15 min. A solution of potassium cyanide (128.3 g, 1.90 mol) in water (300 ml) was added dropwise to a stirred solution of copper (II) sulphate pentahydrate (118.1 g, 0.48 mol) in water (300 ml) and ice (300 g) at 10-20°C. Sodium hydrogen carbonate (265.1 g, 3.16 mol) and cyclohexane (450 ml) were added, the temperature was raised to 50°C and the cold diazonim salt mixture was added in portions with rapid stirring. The mixture was cooled, the organic layer was separated and the aqueous layer was washed with ether (twice) . The combined organic phases were washed with water, 10% sodium hydroxide, water and dried (MgSO ). The solvent was removed in vacuo to afford a dark brown solid (78.0g) which was steam distilled to give an off-white solid. Step A33 A solution of the Grignard reagent, prepared from 4-bromo- octylphenyl ether (122.6 g, 0.43 mol) and magnesium (11.96 g, 0.49 mol) in dry THF (300 ml) was added dropwise to a stirred, cooled (-78°C) solution of tri-isopropyl borate (161.7 g, 0.86 mol) in dry THF (50 ml) under dry nitrogen. The stirred mixture was allowed to warm to room temperature overnight and was then stirred at room temperature for lh with 10% hydrochloric acid (300 ml). The product was extracted into ether (twice), the combined ethereal extracts were washed with water and dried (MgSO ' ). The solvent was removed in vacuo to yield a cream-coloured solid which was recrystallised from water to give colourless crystals. A solution of the above (0.076 mol) in ethanol (90 ml) was added dropwise to a stirred mixture of the product of Step A32 (15.0 g, 0.069 mol) and tetrakis( riphenylphosphine) addadium(0) (2.38 g, 2.06 mmol) in benzene (130 ml) and 2M-sodium carbonate (100 ml) at room temperature under dry nitrigeπ. The stirred mixture was heated under reflux (90-95°C) for 4.5h (ie, until glc analysis revealed absence of starting material). The mixture was cooled and stirred for 1 h at room temperature with 30% hydrgoen peroxide (2 ml). The mixture was further cooled to 2°C, and the product was filtered off and washed with water. The product was dried (CaCl ) in vacuo to give fawn-coloured needles. Step A34 The product of Step A33 was hydrolysed to the acid by con¬ ventional reflux with 50% hydrochloric acid and tol ene, until glc analysis revealed absence of the nitrile starting compound. At the end of this time the acid liquid was cooled to room temperature. The organic layer was separated and further purification was as Step A13. The carboxylic acid product of Step A34 was made into the product via route E, using a procedure analogous to example I above. Example 9 • Steps A* L F F A solution of n-butyllithium (6.60 ml, 10.0M in hexane) was added dropwise to a stirred, cooled (-78 C) solution of 1,2-difluoro- benzene (7-50 g) in dry THF (70 ml) under dry 1 2 The stirrel mixture was maintained under these conditions for 2 hours and then a cooled solution o^ tri-isopropyl bor te ( .^2 g) in dry THF (50 ml) was added dropwise at -78 C. The stirre^ mixture was allowe-! to warm to room temperature overnight and then stirre^. for 1 hour at room temp¬ erature with 10 % HC1 (50 ml) . The product was extracted twice into ether and the combined extracts were washed with water twice and drie (i-lgSO^). Solvent was removed in vacuo to yield an off-white solid yield = 9 ~ . Step A42 r __. • -OH 5 The method used was that of M F Hawthorne , J Org. Chem . (1957) , 22 , 1001 Quantities: A l product 4 A0 g 10 % hydrogen peroxide 30 ml Yield : 2.01 g, (80 %) , off-white solid, mp 3 -3 °C 10 Step A 3 F F A solution of 1-bromohexane (9-33 g) in acetone (20 ml) was added dropwise to a stirred solution of A-4-2 product (6.12 15 g) and potassium carbonate (13-5 g) in acetone ( 75 ™l) s-t room temperature. The stirred mixture was refluxed for 21 hours (complete reaction by TLC). The product was extracted twice into ether and the combined extracts were washed with water, lOό sodium hydroxide, water, and dried ( ~~ εβ0^) . Solvent was 20 removed in vacuo and the residue was distilled (o.l mm Hg) to yield a colourless liquid (9 * 3 ) . Step A* F F (0H) 2 B-^-0C 6 H i;? -n ~ 5 The experimental conditions for this step were the same as step A4l above. Steps A^ and A 6 F F The method used was that of steps A12 and A13 described above. 5 The procedure followed was analogous to that described above. By a similar procedure the n-C o H_._0- analogue was prepared. 0 5 Q 5 An example of the use of a compound of Formula I in a liquid crystal material and device embodying the present- inven¬ tion will now be described with reference to Figure 8 In Figure 8 a liquid crystal cell comprises a layer 1 of liquid crystal material exhibiting a chiral smectic phase sand¬ wiched between a glass slide 2 having a transparent conducting layer3 on its surface, eg of tin oxide or indium oxide, and a glass slide having a transparent conducting layer 5 on its surface. The slides 2,4 bearing the layers »5 are respec- tively coated by films 6,7 of a polyimide polymer. Prior to construction of the cell the films 6 and7 are rubbed with a soft tissue in a given direction the rubbing directions being arranged parallel upon construction of the cell. A spacer 8 eg of polymethyl methacrylate, separates the sli es 2, 4 to the required distance, eg 5 microns. The liquid crystal material 1 is introduced between the slides 2,4 by filling the space between the slides 2, and spacer 8 an< i sealing the spacer 8 in a vacuum in a known way. Preferably the liquid crystal material is in the smec¬ tic A, nematic or isotropic liquid phase (obtained y heating the material) when it is introduced beteen the slides 2,4 to facilitate alignment of the liquid crystal molecules with the rubbing directions on the slides 2,4« A polarizer 9 is arranged with its polarization axis parallel to the rubbing direction on the films 6,7 an an analyzer (crossed polarizer) 10 is arranged with its polar¬ ization axis perpendicular to that rubbing direction. When a square wave voltage (from a conventional source not shown) varying between about +10 volts and -10 volts is applied across the cell by making contact with the layers ~ and 5 the cell is rapidly switched upon the change in sign of the - voltage between a dark state and a light state as explained above. In an alternative device (not shown) based on the cell construction shown in Figure the layers 3 aπt ^ 5 ma y be - selectively shaped in a known way, eg by photoetchiπg or deposition through a mask, eg to provide one or more display symbols, eg letters, numerals, words or graphics and the like as conventionally seen on displays. The electrode portions formed thereby may be addressed in a variety of ways which include multiplexed operation. The liquid crystal mixtures described in examples 1 to 6 above were found to be suitable for use as the layer 1.

Claims: CLAIMS 1. A cyanohydrin derivative of general formula I: wherein R is selected from hydrogen, C - C alkyl, alkoxy, per- fluoroalkyl and perfluoroalkoxy and may be straight chain or 2 branched chain; R is alkyl, which may be C - C_ straight chain, 1 8 C - C branched chain or cyclic; r is an integer 1 to 10, n and m are independently 0 or 1; with the provisos that: if both n and m are O then X is selected from: where the (F)*s indicate that X carries one or two fluorine sub- stituents in any one or two of the available lateral substitution positions on the indicated phenyl rings.p is O or 1, Z is a single bond where p is O and COO when p is 1, and; if one or both of n or m are 1 then X is a group of general formula: . ( -ø,.),^ . ) ( _^) where each ring A, B and C is independently selected from phenyl, fluoro or chloro substituted phenyl, cyclohexyl, pyrimidyl, pyridyl or dioxanyl, each link A, B and C is indenpendently a single bond, COO, OOC, CH CH , CH=N, N=CH, CH 0, OCH or O, and each of a, b and c is O or 1 provided (a + b + c) is 2 or 3. 2. A cyanohydrin derivative according to claim 1, characterised by a general formula II: 2 -R II wherein R is selected from C - C alkyl or alkoxy; R , r, n and m are as defined in formula I, with the provisos that: if both n and m are O then X is selected from: 2. (contd. ) (F) where p and Z and their relationship are as d e ined in formula I. and (F) indicates that the biphenyl system carries one or tvro fluorine substituents on any one or two of the available substitution positions of the biphenyl system, and ? if one or both of n or are 1 the X is a group of general formula -( ~ y< ~ --(- ~ )- - where each ring A, B and G is independently selected from phenyl, fluoro or chloro substituted phenyl and trans- cyclohexane, c is 0 or 1, B is COO or a single bond, being a single bonl if c is 0. 3- A cyanohydrin derivative according to claim 2, characterise! by a general formula IIA: where E , (F), Z, p and R and their relationship are as defined in formula II. . A cyanohydrin derivative according to claim 3. characteri~e'-i by having one substituent (F). or two in 2, 3 or 2', 3' positions. 5- A cyanohydrin derivative according to claim ^, characterised in that in formula IIA p is 0 and Z is a single bond. 6. A cyanohydrin derivative according to claim 5. characterise! by a formula IIAl: 7- A cyanohydrin derivative according to claim 5 > characterise! by a formula I3A2, IIA - or IIA9: (IIA2) (IIA*"-) (IIA9) —T UT£ SHEET hi 8. A cyanohydrin derivative according to claim 2, characterised by a general formula IIB: wherein R 1 , r, B, σ and R 2 are as defined .in formula II, (F ) indicates that the relevant phenyl ring may carry a fluorine sub ¬ stituent, Q is fluorine or chlorine and d is O or 1. 9- A cyanohydrin derivative according to claim 8, characterised by a formula: CN R 1 -CH=CH-(CH 2 ) r -0- C^.- cN-C00CH-R where r is 1 to 6. 10. A cyanohydrin derivative according to claim 2, characterised by a general formula IIC: wherein R 1, B, C and R2 are as defined inforumla II, (F) indicates that the relevant phenyl ring may carry afluorine substituent, Q is fluorine or chlorine and d is 0 or 1. 11. A cyanohydrin derivative according to claim 10, characterised •by a - f ormul : 12. A cyanohydrin derivative according to claim 2, characterised by a formula II0: 1 2 where R an! R are as defined in formula II 1 • A cyanohydrin derivative according to any one o f the preced- ing claims characterised in that R ,1 1is Ci :- —- Ci . η . n-alkyl. 11 1 - A cyanohydrin derivative according to claim 13, characterised 2 in that R is ^ - Cc n-alkyl. 15- A cyanohydrin derivative according to claim 14, characterise! 2 in that R is methyl. 16. A cyanohydrin derivative according to claim 13 . characterised in that R 2 is an alkyl g•roup of formula R- " ~ ; where w is 0 or an integer 1 to 5 » a -nd each of x and y are indepen¬ dently 1 to 6. 17. A cyanohydrin -derivative according to claim 16, characterise -1 in that w is 0 and at least one of x and y is 1. 18. A cyanohydrin derivative according to claim 17. characterise! in that R 2 is -CH(CH.-.) 2 . 19- A cyanohydrin derivative according to claim 13, characterise! in that R is cyclohexyl. 20. A liqui1 crystal material being a mixture of compounds, char¬ acterised in that at least one is a derivative as claimed in claim 1. 21. A liquid crystal material according to claim 20, characterise! in that at least one of the ' derivatives of formula I has a formula: wherein R 1 is C- - £,_, n-alkyl or n-alkoxy, and R2 is C - C n- alkyl or an alkyl group of formula: where w is 0 or an integer 1 to 5 and each of x and y are indep¬ en lently 1 to 6. 22. A liquid crystal material according to claim 20 or 21, characterised in that the mixture additionally contains at least one compound of formula III: ' * • (F) Ra -- rnλ> ΘO)>--ccoooo--/<S0>--]Rb in .where Ra and R are independently C - C alkyl or alkoxy and (P) indicates that the biphenyl system may carry a lateral fluorine sub¬ stituent. 23. A liquid crystal material according to claim 22 characterised in that the compound of formula III has a formula IIIA: 24. A liquid crystal material according to claim 20 or 21, characterised in that the mixture additionally contains at least one compound of formula IV: where n is 1 or 2 and Ra and Rb are independently C - C alkyl or alkoxy. 25. A liquid crystal material according to claim 24, characterised in that the compound of formula IV has a formula I A: 26. A liquid crystal material according to claim 20 or 21, characterised by containing two derivatives of formula I which have twisting effects of opposite handedness in the smectic C phase. 27. A liquid crystal electrooptic display device, characterised in that it uses a liquid crystal material as claimed in claim 20 or 21. SUBSTITUTE SHEET

Inventors: COATES DAVID, GREENFIELD SIMON, SAGE IAN CHARLES, COATES, DAVID, GREENFIELD, SIMON, SAGE, IAN, CHARLES
Applicants: COATES DAVID, GREENFIELD SIMON, SAGE IAN CHARLES, SECR DEFENCE BRIT, SAGE, IAN, CHARLES, THE SECRETARY OF STATE FOR DEFENCE IN HER BRITANNI
Application year: 1988
Main classification: C07C121
IPC codes: C07C255, C09K19, G02F1