Synthesis and mesogenic properties of 3,6-disubstituted cyclohex-2-en-1-ones Roger Brettle, David A. Dunmur, Louise D. Farrand".? and Charles M. Marson Department of Chemistry, University of Shefield, Shefield, UK S3 7HF A series of 3,6-substituted cyclohex-2-en- 1-ones have been prepared by an efficient convergent Robinson-type annulation route. The cyclohex-2-en-1-one ring is the basis of a novel mesogenic core and when substituted at the 6-position provides a chiral centre, which is adjacent to a strong transverse dipole moment. This system has the advantage that both of the two main features required for new electro-optical applications (a dipole for switching and a chiral centre to reduce the symmetry) are located in the molecular core. The synthesis and mesogenic properties of these novel enones are reported.Extensive research in the liquid-crystal field has been directed towards attempting to correlate the relationship between mol- ecular structure and mesogenic properties.' A systematic way of studying this relationship is to introduce small changes into the chosen mesogenic structure and to observe the effects of different substituents. In the design of liquid crystals for new electro-optical applications this aim has been partially achieved by many researchers who have studied the effect of chirality in optically active systems.2 In particular, new electro-optical applications based on the ferroelectric (Sc*) and electroclinic effects (S,*) have been found to require a high degree of chirality coupled with a large transverse dipole rn~ment.~ Chirality is usually introduced into the molecule by means of a chiral centre incorporated into an aliphatic chain.A closer examination of ferroelectricity in liquid crystals shows that the magnitude of spontaneous polarization depends upon the tilt angle, the size of the dipole at the chiral centre, and the amount of freedom that the chiral centre has to rotate about the long axis of the molecule. In many cases, the effectiveness of the chiral centre in promoting macroscopic chiral properties in liquid crystals has been shown to increase as the chiral centre is brought closer to the rigid molecular The aim of this work was to prepare a range of mesogenic compounds for new electro-optical applications based on chiral smectic liquid crystals, which if enantiomerically enriched will exhibit a large spontaneous polarization.Knowledge of the factors which influence a high spontaneous polarization value suggested a target structure that would combine a chiral centre as part of the rigid core with a transverse dipole in order to reduce the rotation of the chiral centre about its long axis (which if not rigid may reduce the value of spontaneous polarization). In order to produce chiral liquid crystals for a variety of applications, it is possible to use either mesogenic compounds, or non-mesogenic chiral compounds in a suitable liquid-crystal host. It is more desirable to use a chiral smectic material than a non-mesomorphic compound as a dopant in displays because incompatibility between dopant and host material is likely to reduce the effectiveness of the chiral dopants.These considerations suggested a study of the cyclo- hex-2-en-1-one ring system, which, when substituted at the 6-position, provides a chiral centre that is adjacent to a strong transverse dipole moment. In the design of molecules for ferroelectric liquid crystals based on tilted chiral smectics, it is desirable that the electric dipole has a fixed orientation with respect to the molecular core, and that the symmetry breaking chiral element is also rigidly attached to the core. The structures reported here have the advantage that both of the two main t Present address: Merck Ltd., West Quay Road, Poole, UK BHlS 1HX.features required for ferroelectric purposes (a dipole for switch- ing and a chiral centre to reduce the symmetry) are present in the molecular core. 0 I In order to make the system anisotropic, the core can be made longer by substitution of an aromatic ring placed at the 3-position (I). Such substitution also renders the core more polarizable. The aromatic ring may then be further substituted at the 4-position to elongate the molecule (R =alkyl or alkoxy), and the cyclohex-2-en-1-one ring can be substituted at the 6-position to provide an extended calamitic structure with a centrally located chiral centre (R' =alkyl). The 3-arylcyclohex- 2-en-1-one system contains a novel rigid core, and the aim of this work was to determine whether this new system did in fact exhibit mesogenic behaviour when appropriately substi- tuted.The approach was to prepare several racemic modifi- cations of 3-arylcyclohex-2-en-1-onesby a convergent route. This allowed the possibility of preparing as many analogous compounds as possible with minimum structural alterations of the precursors. One route which could permit such con- vergency was a Robinson-type ann~lation.~ The synthetic route chosen would have to provide a variety of analogues in order to allow optimization of the molecular structure to give desired properties, preferably smectic A or smectic C phases, a low transition temperature from the crystal to the smectic phase, and stability over a wide temperature range.The ultimate aim of this work was to prepare optically active liquid crystals, but effort was initially focused on the preparation of racemic compounds in order to establish the mesophase behaviour. The preparation of pure enantiomers of related compounds is described elsewhere.8 Synthesis The arylcyclohex-2-en-1-oneswere prepared as shown by the convergent route in Scheme 1. The phenyl ethers (1, 2) were prepared by alkylation of phenol with the appropriate alkyl bromide according to the literature proced~re.~~~~ Subsequent Friedel-Crafts acylation of the aromatic compounds using 3- chloropropionyl chloride ( 1 equiv) and aluminium trichloride (1.1 equiv) in pentane (20°C, 1h) afforded the P-chloroke- tones (3-7).The short chain-length P-keto esters (R' =C,, C,) (8-10) were obtained by alkylation of the acetoacetate with an alkyl J. Muter. Chern., 1996, 6(5),747-751 747 I 13-23 Scheme 1 Preparation of arylcyclohex-2-en-1-ones halide using sodium methoxide as a nucleophilic base In the reactions with longer chain alkyl halides, R1 =cg, Clo (11, 12), the use of a nucleophilic base served only to cleave ethyl acetoacetate vzu attack at the site of the electrophilic carbonyl group Therefore, the non-nucleophilic base sodium hydride was chosen to replace sodium ethoxide No reaction was observed at 0 or 20"C, however, under reflux in tetrahydro- furan, an extremely clean reaction was observed and both alkylations proceeded in high yields The desired 3-arylcyclohex-2-en- 1-ones ( 13-23) were obtained in a one-pot procedure from the appropriate chloro ketones (3-7) and the keto esters (8-12) The chloro ketone was treated with potassium tert-butoxide in ethanol to generate the enone (11) zn sztu To this mixture was added a mixture of the keto ester (1 equiv) and sodium ethoxide (1 equiv) in ethanol The mixture was stirred under reflux for 3 h, concen- trated and extracted with CH,Cl,, to give an oil which was dissolved in ethyl acetate-light petroleum (1 4) On cooling, white crystals of the desired 3-arylcyclohex-2-en- 1-one ( 13-23) precipitated To our knowledge, this is the first time that 3- arylcyclohex-2-en-1-oneshave been prepared by this [3C +3C] type condensation This convergent condensation has the advantage that the unwanted activating alkoxycarbonyl group is cleaved during the one-pot procedure, presumably by a retro-Claisen process However, in the preparation of 14, minor quantities of the keto ester (14b) were isolated The reaction of ethyl 2-undecylacetoacetate (11) with 1-(4- decylphenyl)-3-chloropropan-l-one(7) was not successful, probably because of the presence of the bulky terminal alkyl chains In general, the alkylphenyl derivatives were isolated in slightly higher yield, and proved easier to isolate than the alkoxy compounds This may be a consequence of the mes- omerism involving the 4'-alkoxy substituent further dimin- ishing the already low electrophilicity of the carbonyl group of the vinyl ketones (11) Instrumentation and procedures Moisture-sensitive reactions were conducted in oven-dried glassware assembled under a positive pressure of argon Solvents were dried according to literature methods Thin-layer chromatography (TLC) was used to monitor the extent of the reaction and was performed on type 5244 Merck 0 2 mm 748 J Muter Chem, 1996, 6(5),747-751 aluminium-backed silica plates The plates were visualized using UV light or iodine vapour Column chromatography was performed with silica gel (Sorbsil 60) as the stationary phase Organic solutions were dried over anhydrous mag- nesium sulfate Evaporation refers to removal of the solvent under reduced pressure 'H NMR spectra were recorded using a Bruker AC250 (250 MHz) with the residual proton signal of chloroform 6= 7 25 as the internal standard, 13C NMR spectra were obtained on a Bruker AC250 instrument operating at 62 9 MHz 13C shifts were measured in ppm relative to the central peak of deuteriochloroform at 6 =77 0 Mass spectra were obtained on a Kratos MS-25 instrument Microanalytical data were obtained on a Perkin-Elmer 2400 CHN analyser The phase assignments13 and transition temperatures were determined by thermal polarized light microscopy using a Zeiss Universal microscope equipped with crossed polarizers and a Linkam hot-stage with an integrated temperature con- troller Heating and cooling rates were usually 5 or 10 "C min Differential scanning calorimetry (DSC) was performed using a Perkin-Elmer DSC-7 at scan rates of 10 min-' Sample masses of between 1 and 2 mg were typically used Onset temperatures were taken as transition tempera- tures, and they and the associated thermodynamic parameters were usually taken from the second heating cycle Experimental Butyloxybenzene (1) Prepared as described in the literature' and was obtained as a clear, colourless liquid (74%), bp 41 "C, 0 4 mmHg (lit ,9 bp 82-83 5 "C, 10 mmHg) Hexyloxybenzene (2) Prepared according to the literature procedure lo A clear, colourless liquid was isolated (84%), b p 80 "C, 0 4 mmHg (lit ,lo bp 118-124 "C, 12 mmHg), Cl2HI80 requires C, 80 90, H, 10 11%, Found C, 81 03, H, 10 24% l-[(4-HexyZoxy)phenyl]-3-chloropropun-l-one(3) A solution of hexyloxybenzene ( 15 0 g, 84 mmol) in pentane (30 cm3) was added to an ice cooled slurry of aluminium chloride (12 7 g, 95 mmol) in pentane (50 cm3) 3-Chloropropionyl chloride (8 0 ml, 84 mmol) was dripped into the slurry After stirring at room temperature for 1 h, water (100cm3) was added to quench the reaction The pentane layer was removed and washed with water (50 cm3) The first aqueous layer was washed with an equal amount of pentane The organic extracts were dried and evaporated off to give a brown oil which was dissolved in ethyl acetate Addition of light petroleum to the solution precipitated 3 as greenish-brown crystals (19 3 g, 85%), mp 43-44 "C, (lit ,14 m p 31-34 "C) Cl,H210,Cl requires C, 67 03, H, 7 87, Cl, 13 19%, Found C, 66 73, H, 7 83, C1, 1308% 6, 793 (2H, d, J=8), 691 (2H, d, J=8), 401 (2 H, t, J=6), 3 91 (2 H, t, J=6), 3 40 (2 H, t, J=6), 170 (2 H, quintet, J =6), 1 52-1 25 (6 H, m), 0 90 (3 H, t, J =6) 6, 195 2 (s), 1662 (s), 130 3 (d), 129 3 (s), 114 3 (d), 68 3 (t), 41 0 (t), 39 0 (t), 31 5 (t), 29 0 (t), 25 6 (6), 22 5 (t), 14 0 (9) m/z (+CI) 269 (M+, 76), 233 (42), 205 (52), 121 (100%) Similarly prepared were 1-[(4-Buty/oxy)phenyl]-3-chloropropan-l-one (4) White prisms (85%), m p 54-55 "C, (lit ,14 m p 54 "C) 1-(4-Hexy/phenyl)-3-chloropropun-l-one(5) White prisms (67%), m p 40-41 "C C19H290C1 requires C, 71 27, H, 8 37, Cl, 1402Y0, Found C, 71 30, H, 8 28, C1, 13 86% 1-(4-Heptylphenyl)-3-chloropropun-1-one (6) White prisms (67%), m p 36-37 "C C16H,,0CI requires C, 72 03, H, 8 69, C1, 13 29%, Found C, 72 08, H, 8 44, C1, 13 13% 1-(4-Decylphenyl)-3-chloropropun-l-one (7).Large white needles (97%), m.p. 59-60 "C. C,,H,,OCl requires C, 73.88; H, 9.46; C1, 11.48%; Found C, 73.88; H, 9.37; C1, 11.47%. The following were prepared according to literature procedures. Ethyl 2-pentylacetoacetate (S)." 76%, b.p. 72-74 "C, 0.4 mmHg, (lit.,I6 b.p. 121 "C, 10 mmHg). Ethyl 2-allylacetoacetate (9).1757%. The 'H and I3C NMR data were in accordance with those reported in the literature." Methyl 2-propylacetoacetate ( 10). Isolated as a clear, colour- less oil (65%), b.p. 101 "C, 0.7 mmHg. 6,: 3.75 (3 H, s), 3.44 (1 H, t, J=8), 2.23 (3 H, s), 1.90-1.79 (2 H, m), 1.38-1.24 (2 H, m), 0.93 (3 H, t, J=7).6,: 203.0 (s), 170.2 (s), 59.2 (d), 52.1 (q), 29.9 (t), 28.3 (q), 20.5 (t), 14.3 (9). Ethyl 2-undecylacetoacetate (11). A solution of ethyl aceto- acetate (3.90 g, 30 mmol) in THF (40 cm3) was added to a stirred suspension of sodium hydride (80% in oil) (0.83 g, 30.0 mmol) in THF (50 cm3) at 0 "C. After 1h, a solution of 1-iodoundecane (8.47 g, 30.0 mmol) in THF (20 cm3) was added and the solution was stirred at room temperature for 2 h. The solution was then stirred overnight under reflux and a white precipitate appeared. The mixture was allowed to cool, the solvent removed, and the residue taken up into dichloro- methane (50 cm3), washed with water (2 x 50 cm3) and dried. Evaporating off the solvent afforded a viscous oil, which was subjected to flash column chromatography using dichloro- methane: hexane (2 : 1) as eluant (R,0.51) to give a colourless oil which crystallized on standing.Recrystallization from light petroleum afforded 11 as colourless crystals (7.01 g, 82%), m.p. 31 "C, (lit.,', b.p. 145-15OoC, 1.0mmHg). 6,: 4.18 (2 H, q, J= 7), 3.37 (1 H, t, J=7), 2.40 (3 H, t, J=7), 2.09 (3 H, s), 1.57 (2 H, quintet, J=7), 1.32-1.17 (16 H, m), 0.9 (3 H, t, J=7). 6,: 204.2 (s), 167.0 (s), 61.2 (t), 60.0 (d), 43.8 (t), 31.9 (t), 29.8 (q), 29.4 (t), 29.4 (t), 29.3 (t), 29.2 (t), 28.2 (t), 27.4 (t), 23.9 (t), 22.7 (t), 14.1 (2) (9). ~,,,/cm-~ (Nujol mull) 2920 (C-H), 1720 (C=O), 1430 (C-H), 1380 (C-H). Similarly prepared was: Ethyl 2-hexylacetoacetate (12)." 77%, b.p.100-102 "C, 0.07 mmHg, (lit.," b.p. 127-129 "C, 10 mmHg). 3-(4-Butyloxyphenyl)-6-propylcyclohex-2-en-1-one ( 13). 1-(4-Butyloxyphenyl)-3-chloropropan-l-one(2.25 g, 9.4 mmol) was treated with potassium tert-butoxide (1.05 g, 9.4 mmol) in super-dry ethanol. In a separate flask, methyl 2-propylaceto- acetate (1.48 g, 9.4 mmol) was added to a solution of sodium (0.23 g, 10 mmol) previously dissolved in ethanol (30 cm'). This solution was then added to the first ethanolic solution. The reaction was heated under reflux for 3 h, and then cooled and concentrated to give a brown oil which was dissolved in dichloromethane (100 cm3) and washed with brine (2 x 50 cm3). The organic layer was removed and dried, then concentrated to give a yellow oil.The oil was dissolved in ethyl acetate; light petroleum was then added and the solution was left to stand in a freezer for 24 h. The white precipitate was collected by vacuum filtration. Recrystallization from ethyl acetate and light petroleum gave 13 as a white crystalline solid (1.27 g, 46%). C1,H2,02 requires C, 79.68; H, 9.15%; Found C, 79.82; H, 9.10%. 6,: 7.50 (2H, d, J=8), 6.90 (2H, d, J= 8), 6.35 (1 H, m), 3.97 (2H, t, J=6), 2.85-2.65 (2H, m), 2.32 (1 H, m), 2.23 (1 H, m), 1.87 (2 H, m), 1.83 (2 H, quintet), 1.52 (2 H, sextet), 1.40 (3 H, m), 1.00-0.92 (6 H, m). 6,: 202.1 (s), 160.8 (s), 157.7 (s), 130.4 (s), 127.5 (d), 123.2 (d), 114.6 (d), 67.8 (t), 45.3 (d), 31.5 (t), 31.2 (t), 27.7 (t), 26.8 (t), 20.2 (t), 19.2 (t), 14.2 (q), 13.8 (9).m/z (+CI) 287 (M', 70), 244 (100%). Similarly prepared were: 3-(4-Butyloxyphenyl)-6-pentylcyclohex-2-en-l-one ( 14). White prisms (41%). C21H30O2 requires C, 80.21; H, 9.62%; Found C, 79.91; H, 9.78%. 3-(4-Butyloxyphenyl)-6-pentyl-(6-ethoxycarbonyl)cyclohex-2-en-1-one (14b). Yellow crystals (12%), m.p. 61 "C. C24H3404 requires C, 74.58; H, 8.87%; Found C, 74.61; H, 8.72%. 6,: 196.4 (s), 171.8 (s), 161.0 (s), 157.5 (s), 129.8 (s), 127.6 (d), 114.6 (d), 67.8 (t), 61.1 (t), 56.1 (s), 33.7 (t), 32.2 (t), 31.2 (t), 29.8 (t), 25.2 (t), 24.2 (t), 22.4 (t), 19.2 (t), 14.1 (q), 14.0 (q), 13.8 (4). 3-(4-Hexyloxyphenyl)-6-allylcyclohex-2-en-1-one (15).Prisms (45%). C21H2802 requires C, 80.73; H, 9.03%; Found C, 80.75; H, 9.00%.3-(4-Hexyloxyphenyl)-6-propylcyclohex-2-en-1 -one ( 16).Prisms (39%). C21H3OO2 requires C, 80.21; H, 9.62%; Found C, 80.06; H, 9.51%. 3-(4-Hexyloxyphenyl)-6-pentylcyclohex-2-en-1-one ( 17). Prisms (46%). C&&2 requires C, 80.66; H, 10.01%; Found C, 80.58; H, 10.31%. 3-(4-Hexylphenyl)-6-propylcyclohex-2-en-1 -one ( 18). Fine prisms (43%). HRMS, C21H3oO requires 298.2295; M+ found 298.2297. 3-(4-Hexylphenyl)-6-pentylcyclohex-2-en-l-one(19). Prisms (47%). C24H360 requires C, 84.65; H, 10.66%; Found C, 84.74; H, 10.80%. 3-(4-Heptylphenyl)-6-pentylcyclohex-2-en-1 -one (20).Microprisms (47%). C24H360 requires C, 84.65; H, 10.66%; Found C, 84.74; H, 10.80%. 3-(4-Heptylphenyl)-6-hexylcyclohex-2-en-1 -one (21).Microprisms (45%).C2,H3,0 requires C, 84.69; H, 10.80%; Found C, 84.73; H, 10.93%. 3-(4-Decylphenyl)-6-propylcyclohex-2-en-1-one (22).Microprisms (46%). HRMS, C2sH380 requires 354.2919; M+ found 354.2923. 3-(4-Decylphenyl)-6-pentylcyclohex-2-en-l-one(23). Prisms (45%). C27H420 requires C, 84.75; H, 11.06%; Found C, 84.51; H, 11.06%. Liquid-crystal Properties The transition temperatures of the mesogenic cyclohex-2-en- 1-ones are listed in Table 1. Phase types were identified by the optical texture^.'^ and phase transitions and temperatures were confirmed by DSC. All of the homologues synthesized exhibited smectic A phases, which can be attributed to the presence of a localized dipole in the core of the molecule. All of the smectic A phases were observed as the common focal-conic fan texture.This texture was always seen to separate from the isotropic, on cooling in the form of battonets, which themselves consist of growing focal-conic domains. A texture characteristic of all compounds exemplified by compound 21 is shown in Plate 1. DSC analyses show that the values obtained for the enthalpy change from the smectic A to the isotropic liquid are quite large, typically 5-8 kJ mol-I, which are within the expected range of values for a smectic A to isotropic transition. All of the alkoxyphenyl cyclohex-2-en- 1-ones exhibited rela- tively low K+SA (40-60 "C) transition temperatures. The smectic A phases were maintained over a wide temperature range, typically 20-60 "C. The relatively short compound (13) exhibited a crystal to crystal transition before exhibiting a J.Mater. Chem., 1996, 6(5), 747-751 749 Table 1 Phase types and transition temperatures of cyclohex-2-en-l-ones (R and R' as in Scheme 1) transition temperature enone R R' (optical microscopy)/"C 13 C3H7 K(60.1)Kz( 68.2)S~( 97.1 )I 14 C5H1 1 15 C3H5 K(48.9)SA( 63.2)I 16 C3H7 K(45.O)S,(96.2)1 17 C5H11 18 C3H7 19 C5H11 20 GHl, 21 C6H13 22 C3H7 I(36.0)s~(32.O)K monotropic 23 C5H11 K(48.3)SA(63.1)I Plate 1 Focal-conic fan texture of the smectic A phase of compound 21 formed at 60°C on cooling from the isotropic phase Fig. 1 Stackbar chart to illustrate the phase types and transition temperatures of the cyclohex-2-en- l-ones smectic A phase.The liquid-crystal properties of this compound may verge on the limits of anisotropic requirements for liquid- crystal behaviour since the known compound 3-(4-ethoxy-phenyl)-6-methylcyclohex-2-en-l-one is not mesogenic.20 No mesogenic properties were observed for compound 14b, the isolated cyclohex-2-en- l-one keto ester, which has a melting point of 62°C. The alkyl chain in 15 contains a double bond. A comparison with compound 16, which does not possess a 750 J. Muter. Chem., 1996, 6(5), 747-751 T onset/"C AH/kJ mol-' AS/J K-' mol-I 53.6 7.6 23.2 64.6 10.3 31.0 89.5 7.5 20.7 42.8 20.3 54.3 63.1 7.9 20.8 47.5 17.6 64.9 59.5 5.2 15.6 46.4 14.6 45.7 89.9 6.9 19.0 51.1 15.7 48.4 102.2 8.1 21.6 27.1 13.8 46.3 33.2 6.3 20.5 21.2 10.3 34.8 59.3 6.2 18.7 21.5 11.0 37.4 60.0 6.9 20.7 43.6 33.3 105.2 57.5 5.6 17.1 34.7 37 9 123.2 43.8 38.9 122.8 59.4 7.3 21.9 double bond in the terminal chain, shows that the main effect of the alkene is to lower the clearing point considerably.It is known that liquid crystals with alkenyl side chains are chemi- cally and photochemically stable as long as the double bond is not conjugated.21 All of the alkylphenyl cyclohex-2-en- l-ones prepared were stable and showed no decomposition during heating and cooling cycles. In general, the alkylphenyl derivatives exhibited both lower melting and clearing transition temperatures than the alkoxy homologues.Compounds 18, 19 and 20 exhibited extremely low temperature crystal to smectic A transitions. The smectic A phases were observed over a 10-30°C range. The optimum alkyl chain lengths were hexyl with pentyl, and heptyl with pentyl. Enone (22),which has a large difference in alkyl chain lengths within the molecule, possesses a monotropic smectic A phase. When R' is increased to C5Hll, as in enone (23), a smectic A phase is observed on heating and cooling. These results indicate that it is likely that appropriate modifi- cation of the groups attached to the arylcyclohex-2-en-1 -one core will result in the formation of liquid-crystal phases of other symmetries. Optically active mesogens based on alkyl- phenyl cyclohex-2-en- l-ones have been prepared using highly efficient enzymic resolution of acetoxy-derivatives, and the synthesis and mesophase properties of these have been described previously.* Direct comparison of the mesophase properties of the racemic compounds reported in this paper with the optically active compounds previously reported is not possible since the terminal groups are different. However, both series of mesogens exhibit smectic A phases, the optically active carbonyloxy-compounds having higher melting points and shorter mesophase ranges, possibly due to their increased dipole moments.Conclusions A series of new mesogenic compounds based on the novel core structure of phenylcyclohex-2-en-1 -one has been prepared.The core structure was chosen to combine a lateral dipole moment in the core with a chiral centre, although the compounds reported in this paper were all prepared as racemates. All compounds of this series showed smectic A phases below 100"C: those having alkoxy-chain substituents generally had higher transition temperatures and wider smectic A ranges. Increasing the alkyl chain length beyond seven carbon atoms diminished the liquid crystallinity of the materials. The dis- covery of a new basic core material should allow the prep- aration of many more liquid crystals having a variety of properties. The fact that these mesogens have relatively low melting point temperatures is also of significance in the devel- opment of new materials for applications.The cyclohex-2-en- 1-one core introduces two new structural features, which can be useful in particular display devices, since a transverse dipole moment rigidly linked to a chiral centre is necessary for the appearance of ferroelectricity in chiral smectic C phases and for electroclinism in chiral smectic A phases. Both these phenomena can be used as a basis for new liquid-crystal devices. The present route to 6-alkyl-3-arylcyclohex-2-en-l-ones complements the synthesis of chiral 6-carbonyloxy-3- arylcyclohex-2-en- 1-ones as previously reported.* We thank Hitachi Research Laboratory, Hitachi Ltd., Japan, for financial support of this work. References 1 J. W. Goodby, J. Mater. Chem., 1991,1,307. 2 J. W. Goodby, I.Nishiyama, A. J. Slaney, C. J. Booth and K. J. Toyne, Liq. Cryst., 1993, 14, 37. 3 H. Stegemeyer, R. Meister, H-J. Altenbach and D. Szewczyk, Liq. Cryst., 1993, 14, 1007. 4 J. W. Goodby, J. S. Pate1 and E. Chin, J. Phys. Chem., 1987, 91, 5151. 5 S. Takehara, M. Osawa, K. Nakamura, T. Kusumoto, K-I. Sato, A. Nakayama and T. Hiyama, Ferroelectrics, 1994,148,195. 6 K. Itoh, M. Takeda, M. Namekawa, S. Nayuki and Y. Murayama, T. Yamashi and T. Kitazume, Ferroelectrics, 1993,148,85. 7 W. S. Rapson and R. Robinson, J. Chem. SOC., 1935,1285. 8 R. Brettle, D. A. Dunmur, L. D. Farrand and C. M. Marson, J. Chem. SOC. Chem. Commun., 1994,2041. 9 E. Profft, Chem. Abstr., 1959,53,2222. 10 M. Protiva, M. Radsner, E. Aolerova, V. Seidlova and Z. J. Vejoelek, Chem. Abstr., 1965,62, 524c. 11 F. J. Marshall and W. N. Cannon, J. Org. Chem., 1956,21,245. 12 R. Brettle, D. A. Dunmur, L. D. Farrand, N. J. Hindley and C. M. Marson, Chem. Lett., 1993, 1663. 13 D. Demus and L. Richter, Textures in Liquid Crystals, Verlag Chemie, Weinheim, 1980. 14 N. J. Hindley, PhD Thesis, University of Sheffield, 1991. 15 A. I. Vogel, A Textbook of Practical Organic Chemistry, Longman, Harlow, 5th edn., p. 620. 16 A. J. Birch and R. Robinson, J. Chem. SOC., 1942,494. 17 D. Gravel and M. Labelle, Can. J. Chem., 1985,63,1875. 18 Beilstein, 3rd suppl., vol. 3, p. 1269. 19 Beilstein, 1st suppl., vol. 3, p. 252. 20 V. S. Bezborodov and D. A. Trohimets, Zh. Org. Khim., 1991, 27, 1958. 21 M. Schadt, R. Buchecker and A. Villiger, Liq. Cryst., 1990,7, 519. Paper 5/06286A; Received 22nd September 1995 J. Mater. Chem., 1996, 6(5),747-751 751