Synthesis and mesomorphic properties of four-ring liquid crystals containing cyclohexyl,phenyl and pyridyl units

Two series of chiral and achiral 4-[(3-n-alkoxycarbonylpyridyl)-6-ethynyl]phenyl 4-(trans-4-n-alkylcyclohexyl)benzoate liquid crystals have been synthesized. Their mesomorphic properties were observed and measured by polarizing optical microscopy and DSC. A broad chiral smectic C phase was observed when terminal chains contained a chiral centre.     

Synthesis and mesomorphic properties of three- and four-ring liquid crystals containing cyclohexyl, phenyl and pyridyl units

Two series of 4-(3-alkoxycarbonylpyridyl-6-ethynyl)phenyl trans-4-n-alkylcyclohexylcarboxylates and 4-(3-alkoxycarbonylpyridyl-6-ethynyl)phenyl 4-(trans-4-n-alkylcyclohexyl)benzoates have been prepared. Their mesmorphic properties were observed and measured by polarizing optical microscopy and differential scanning calorimetry. The relationship between structures and properties is discussed, showing that the ferroelectric phase can be observed when chiral terminal chains exist.     

Synthesis of 3-alkoxycarbonylaminomethylcarbonylamino-4-benzoyl-1,2-dihydropyridines and their cyclization to 5-phenyl-1,3,8,9-tetrahydro-2H-pyrido[3,4-e]-1,4-diazepin-2-ones

The regiospecific reaction of 3-benzyloxycarbonylaminomethylcarbonylamino-4-benzoylpyridine (6a) , or 3-t-butoxycarbonylaminomethylcarbonylamino-4-benzoylpyridine (6b) , with either acetyl chloride or ethyl chloroformate, and either n-butylmagnesium chloride or phenylmagnesium bromide afforded the respective 1-acetyl (or ethoxycarbonyl)-2-n-butyl (or phenyl)-3-benzyloxy (or t-butoxy) carbonylaminomethylcarbonylami-no-4-benzoyl-1,2-dihydropyridines 7 in 60-75% yield. Reaction of 1-acetyl (or ethoxycarbonyl)-2-n-butyl (or phenyl)-3-t-butoxycarbonylaminomethylcarbonyl-4-benzoyl-1,2-dihydropyridines 7b, 7f, 7d, 7h with trifluoroacetic acid gave the corresponding 5-phenyl-8-acetyl (or ethoxycarbonyl)-9-n-butyl (or phenyl)-1,3,8,9-tetrahydro-2H-pyrido[3,4-e]-1,4-diazepin-2-ones 8a, 8b, 8c, 8d respectively in 45–63% yield. N¹-Methylation of 5-phenyl-8-acetyl-9-n-butyl (or phenyl)-1,3,8,9-tetrahydro-2H-pyrido[3,4-e]-1,4-diazepin-2-ones 8a, 8b using sodium hydride and iodomethane yielded the corresponding N¹-methyl derivatives 9a (48%) and 9b (54%). Oxidation of 5,9-diphenyl-8-ethoxycarbonyl-1,3,8,9-tetrahydro-2H-pyrido[3,4-e]-1,4-diazepin-2-one (8d) using p-chloranil afforded 1,3-dihydro-5,9-diphenyl-2H-pyrido[3,4-e]-1,4-diazepin-2-one (10) . 5-Phenyl-8-acetyl-9-n-butyl-1,3,8,9-tetrahydro-2H-pyrido[3,4-e]-1,4-diazepin-2-one (8a) and the corresponding 8-ethoxycarbonyl analog 8c exhibited weak anticonvulsant activity indicating that 8a and 8c may be acting at the same site as the 7-halo-1,4-benzodiazepin-2-one class of compounds.     

Optical and dielectric properties of antiferroelectric liquid crystals and their surface effects

Abstract

A detailed study of the dielectric and optical properties of the ferroelectric liquid crystal material (R)-4′-(3-methoxycarbonyl-2-propoxycarbonyl)phenyl 4-(4-(n-octyloxy)phenyl)benzoate (3MC2PCPOPB) has been carried out. It has been found that an anomalous temperature dependence of the dielectric constant in 3MC2PCPOPB is due to the antiferroelectric and ferrielectric properties. A T(temperature)-E(electric field) phase diagram has been obtained on the basis of the apparent tilt angle measurements. In a thin cell (< 3 μm), both ferroelectric and antiferroelectric domains are simultaneously observed over a wide temperature range, and the complete antiferroelectric phase does not appear even at low temperature. A characteristic texture in which boundary focal conics are aligned parallel to a smectic layer has been observed. The movement of the zig-zag defect line caused by the application of the voltage is also observed.     

Synthesis and Physical Properties of New Ferroelectric Liquid Crystals Consisting of 2(S)-[2 (S)-Methylbutyloxy] Propanol

New ferroelectric liquid crystals containing two chiral centers, 4-(4′-n-alkyloxyphenyl)phenyl 4-{2(S)-[2(S)-methylbutyloxy]propoxy}benzoate ( 4a-4f ) and 4 -(n-alkyloxy)phenyl 4-{4′-[2(S)-(2(S)-methylbutyloxy)propoxy]phenyl}benzoate ( 5a-5f ) were synthesized and their physical properties studied. A phase-transition sequence of C-Sc*-N*-I was observed in most cases. Some homologues of them, 4a-4d , possess monotropic Sc * phase. Not only the Sc* phase-transition temperature of 5a-5f is lower than that of the corresponding 4a-4f , but their Sc * phase-transition temperature range is also wider than the corresponding 4a-4f . The Sc * phase temperature range can be up to 48 °C. The spontaneous polarization of 8-28 nC/cm² and the electric rise time of 240-420 μs were measured in FLCs 4a-5f .     

Synthesis,characterisation and liquid crystalline properties of some Schiff base and cinnamate central linkages involving 1,3,5-trisubstituted pyrazolone ring system and their Cu(II) complexes

Two new mesogenic homologous series, each containing 1,3,5-trisubstituted pyrazolone derivatives, 4-n-alkoxyphenyl and Schiff base–cinnamate central linkages, have been synthesised to give 4-[(5-hydroxy-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl) methyleneamino] phenyl 3-(4-n-alkoxyphenyl)acrylate [Series-A] and 4-[(5-hydroxy-3-methyl-1-p-tolyl-4,5-dihydro-1H-pyrazol-4-yl)methyleneamino] phenyl 3-(4-n-alkoxyphenyl)acrylate [Series-B] and their Cu(II) complexes have also been synthesised. These compounds were characterised by elemental analysis, Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (¹H NMR), carbon-13 NMR (¹³C NMR) and ultraviolet (UV)-visible and mass spectral studies. Their mesomorphic behaviour was studied by polarising optical microscope (POM) with a heating stage. POM data were compared with differential scanning calorimetry thermograms. In Series-A and -B, all compounds exhibit mesomorphism. Series-A compounds exhibit an enantiotropic nematic mesophase except propyl derivative, while a smectic A (SmA) mesophase is observed from the heptyl derivative and persists up to the last member of the homologous series. n-Heptyloxy derivative is monotropic for SmA phase. Series-B compounds also exhibit the enantiotropic nematic mesophase, while the SmA mesophase is observed from the heptyl derivative and persists up to the last member of the homologous series. n-Dodecyloxy derivative exhibits monotropic SmA and nematic mesophases. The mesomorphic properties of both series are compared with each other and the other structurally related compounds. The study reveals that cinnamate linkage containing liquid crystals have higher thermal stability compared to structurally related series containing chalcone linkage. In case of complex series, only one compound from each series gives nematic mesophase.     

Influence of the lateral alkoxy chain length on the gas chromatographic properties of five liquid crystals

The gas Chromatographic properties of five laterally substituted liquid crystals are the subject of a comparative study. These liquid crystals belong to the homologous series: 2-alkoxy-3-methyl-4-(4-ethoxybenzoyl-oxy)-4′-(4-trans-n-pentyclcyclohexanecarboxyloxy) azobenzene, referred to as ALn, where n, the carbon number in the lateral alkoxy chain, is equal to 4, 6, 8, 10, or 12 carbon atoms. Their thermal properties were established by differential scanning calorimetry (DSC). It appears that the introduction of a lateral alkoxy chain affects the nematic temperature range which decreases when the carbon number increases. The chromatographic separation abilities of AL4, AL6, AL8, AL10, and AL12 were studied using capillary glass columns. The five liquid cystals are efficient before and after solid-nematic or nematic-liquid transitions; however, the plate numbers are higher in the nematic state. Interesting analytical properties were noted in various fields: iisomeric separation of alkanes, aromatics, polyaromatics, volatile aroma compounds, and cis and trans isomers. However, the chain length does not exert any great influence on the separation abilities.     

Mesomorphic and photophysical behaviour of 1,3,4-oxadiazole based hockey stick reactive mesogens

New hockey stick mesogens derived from 1,3,4-oxadiazole as a bent-core unit have been synthesised. The molecules resemble hockey stick shape due to the presence of two arms containing a different number of phenyl rings attached with the 1,3,4-oxadiazole bending unit. The shorter arm of the molecule consists of one phenyl ring and 4-n-alkyloxy terminal chains whereas the long arm of the molecule possesses containing two phenyl rings which are linked via imine linkage and reactive 4-n-undecenyloxy as a terminal chain. The thermal stabilities of the newly synthesised compounds were carried out by thermogravimetric analysis (TGA). The mesomorphic behaviour was investigated by polarising optical microscopy (POM) and differential scanning calorimetry (DSC). All the compounds exhibit enantiotropic nematic phase along with smectic phases (SmA and SmC phases). Interestingly, the compounds with lower 4-n-alkyloxy terminal chains (n = 4 and 6) exhibit a wide range of optically isotropic DC phase. On increasing, the terminal 4-n-alkoxy chain length the DC phase disappears. The photophysical properties of the compounds were investigated in different solvents and in the solid state. It was observed that the compound exhibit absorption in UV region and emission in the green region.     

Synthesis and mesomorphic properties of four-ring liquid crystals containing cyclohexyl, phenyl and pyridyl units

Two series of chiral and achiral 4-[(3- n -alkoxycarbonylpyridyl)-6-ethynyl]phenyl 4-( trans -4- n -alkylcyclohexyl)benzoate liquid crystals have been synthesized. Their mesomorphic properties were observed and measured by polarizing optical microscopy and DSC. A broad chiral smectic C phase was observed when terminal chains contained a chiral centre.     

2-[4-Alkenyloxy)phenyl]-5-alkylpyrimidines The relationship between position and nature (E/Z) of the double bond and transition temperatures

Abstract

The 5-n-alkyl-2-[4-(n-alkoxy)phenyl]pyrimidmes are essential components of most commercial chiral smectic C mixtures for electrooptic display devices based on ferroelectric effects. This is due to their generally relatively low melting points, enantiotropic, relatively wide range smectic C mesophases, low viscosity and ease of preparation. An unsaturated carbon–carbon double bond has now been introduced into the terminal alkoxy chain of the 5-n-alkyl-2-[4-(alkoxy)phenyl]pyrimidines to produce the corresponding alkenyloxy substituted derivatives. The position and nature (E/Z) of the double bond has been varied systematically and the effect on the liquid crystal transition temperatures studied. A number of homologous series of the most interesting alkenyloxy substituted materials has been prepared and evaluated. The position and nature (E/Z) of the double bond changes the conformation of the alkenyloxy chain substantially. This can result in significantly higher smectic C transition temperatures for compounds with a trans double bond (E) at an even number of carbon atoms from the molecular core. Significantly lower transition temperatures (including the melting point) are observed for materials with a cis double bond (Z) at an odd number of carbon atoms from the molecular core. Comparisons with the corresponding alkoxy substituted materials (i.e. without a double bond) are made.     

Direct chiral separation of abscisic acid by high-performance liquid chromatography with a phenyl column and a mobile phase containing γ-cyclodextrin

Abscisic acid (2-cis,4-trans-abscisic acid) is a plant hormone that has an asymmetric carbon atom. We tried to separate the enantiomers of native abscisic acid by HPLC using a phenyl column and a chiral mobile phase containing γ-cyclodextrin. The optimum mobile phase conditions were found to be 0.8% (w/v) γ-cyclodextrin, 4% (v/v) acetonitrile, and 20 mM phosphate buffer (pH 6.0). It was found that (R)-abscisic acid was earlier detected than (S)-abscisic acid. Since γ-cyclodextrin is hardly retained on a phenyl column, it was suggested that (R)-abscisic acid formed a more stable complex with γ-cyclodextrin than the (S)-abscisic acid. Abscisic acid in an acacia honey sample was successfully enantioseparated with the proposed method and only (S)-abscisic acid was detected. A biologically inactive 2-trans,4-trans-abscisic acid, which was prepared by irradiation of abscisic acid with a light-emitting diode lamp at 365 nm, was partially enantioseparated by the proposed method. Since the irradiation of (S)-abscisic acid-induced cis-to-trans isomerization to produce one 2-trans,4-trans-abscisic acid enantiomer, it is reasonable that racemization did not proceed during the cis-to-trans isomerization. (S)-Abscisic acid and probably (S)-2-trans,4-trans-abscisic acid were detected in a honey sample, where the peak area of (S)-abscisic acid was 7 times larger than that of (S)-2-trans,4-trans-abscisic acid.     

Synthesis and reactions of some dihydro and tetrahydro-4H-imidazo[5,4,1-ij]quinoline derivatives

Reaction of phenyl N-(8-quinolinyl)carbamate with sodium borohydride afforded 1,2-dihydro-4H-imidazo-[5,4,1-ij]quinolin-2-one, 2a . The 5,6-double bond of 2a was functionalized by reaction with nitrosyl chloride to give the nitroolefin 4 and by reaction with hypobromous acid to give the trans-bromohydrin 5 . Reaction of 5 with sodium azide led to the rearranged trans-6-azido-5-ol 7 , the structure of which was determined by ¹H nmr studies.     

Rod-like Schiff Base Magnetic Liquid Crystals Bearing Organic Radical

4 novel rod-like Schiff base magnetic liquid crystals have been prepared in which trans-bicyclohexyl or trans-cyclohexyl phenyl and biphenyl carboxylic acid phenol ester mesogenic cores with n-propyl and n-pentyl subsfituents were terminated by 4-amino-TEMPO （TEMPO=2,2,6,6-tetramethylpiperidine-l-oxyl）. Of these compounds the silk-like and schlieren textures were found from 4e and 4d by POM （Polarizing Optical Microscope）. DSC （Differential Scanning Calorimeter） measurements show that the mesophase exists from 4-6℃. EPR spectra reveal their paramagnetic properties.     

Dielectric studies of liquid crystals under high pressure III. Low frequency relaxation process in 4-(trans-4′-n-hexylcyclohexyl)isothiocyanato benzene

Abstract

Dielectric studies of 4-(trans-4′-n-hexylcyclohexyl) isothiocyanatobenzene (6CHBT) were performed in the pressure range 0·1–150 MPa, the frequency range 1 kHz–13 MHz and the temperature range 295–325 K. The temperature and pressure dependencies of the static permittivity ?_0∥ and of the relaxation time τ_∥ are analysed and compared with the analogous data obtained recently for 4-n-pentyl-4′-cyanobiphenyl (5CB) (Parts I and II of this series). Marked differences in the dielectric properties of the nematic phases of the two substances are observed. They are interpreted as a result of varying degrees of molecular association in particular compounds. It is concluded that in the nematic phase of 6CHBT dipole–dipole correlations do not exist or are very weak, whereas for 5CB they are easily broken by a relatively low pressure.     

Synthese von Haschisch-Inhaltsstoffen. 5. Mitteilung

A (?)-Δ⁸-6a,10a-trans-tetrahydrocannabinol analogue, with a methyl-(3-dimethyl-amino-propyl)-amino side-chain instead of the n-pentyl radical in the naturally occurring product, has been synthesized by condensing 5-methylamino-resorcinol tosylate with (+)-trans-p-2,8-menthadien-1-ol.     

Die thermische Umlagerung von 2-(Buta-1′,3′-dienyl)-phenolen in 2-Alkyl-2H-chromene; Beispiele für aromatische [1,7a]- und [1,5s]sigmatropische Wasserstoffverschiebungen

2-(1′-cis,3′-cis-)- and 2-(1′-cis,3′-trans-Penta-1′,3′-dienyl)-phenol (cis, cis- 4 and cis, trans- 4 , cf. scheme 1) rearrange thermally at 85–110° via [1,7 a] hydrogen shifts to yield the o-quinomethide 2 (R ? CH₃) which rapidly cyclises to give 2-ethyl-2H-chromene ( 7 ). The trans formation of cis, cis- and cis, trans- 4 into 7 is accompanied by a thermal cis, trans isomerisation of the 3′ double bond in 4. The isomerisation indicates that [1,7 a] hydrogen shifts in 2 compete with the electrocyclic ring closure of 2 . The isomeric phenols, trans, trans- and trans, cis- 4 , are stable at 85–110° but at 190° rearrange also to form 7 . This rearrangement is induced by a thermal cis, trans isomerisation of the 1′ double bond which occurs via [1, 5s] hydrogen shifts. Deuterium labelling experiments show that the chromene 7 is in equilibrium with the o-quinomethide 2 (R ? CH₃), at 210°. Thus, when 2-benzyl-2H-chromene ( 9 ) or 2-(1′-trans,3′-trans,-4′-phenyl-buta1′,3′-dienyl)-phenol (trans, trans- 6 ) is heated in diglyme solution at >200°, an equilibrium mixture of both compounds (～ 55% 9 and 45% 6 ) is obtained.     

Reactions of N-substituted pyridinium carbamoylmethylenides with ethyl arylidenecyanoacetates

Condensation of pyridinium N-alkyl-, N-cycloalkyl-, N-benzyl-, and N-phenethylcarb-amoylmethylenides with ethyl arylidenecyanoacetates stereoselectively gives 4,5-trans-1-alkyl-, 4,5-trans-l-cycloalkyl-, 4,5- trans-1-benzyl-, and 4,5-trans-1-phenethyl-4-aryl-3-cyano-6-oxo-5-(3-R-1-pyridinio)-1,4,5,6-tetrahydropyridin-2-olates. However, pyridinium N-arylcarb-amoylmethylenides react with the same esters without ring closure, yielding Michael adducts, viz., ethyl 3-aryl-4-(N-arylcarbamoyl)-2-cyano-4-(1-pyridinio)butyrates.     

The base-promoted dehydration of rac.-trans-tetrahydro-6-hydroxy-4-[(2-(dimethylamino)ethyl]-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one

The base-catalyzed alkylation of rac.-trans-tetrahydro-6-hydroxy-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one ( 1 ) with dimethylaminoethyl chloride in dimethyl sulfoxide provided predominantly rac.-trans-tetrahydro-6-hydroxy-4-[(2-dimethylamino)ethyl]-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one ( 2 ) and in addition, 2,3-dihydro-4-[2-(dimethylamino)-ethyl]-7-(4-methoxyphenyl)-1,4-thiazepin-5(4H)-one ( 3 ). A plausible mechanism is postulated for the dehydration of the rac.-trans-amide 2 .     

Cyclopentyl derivatives of 8-azahypoxanthine and 8-azaadenine. Carbocyclic analogs of 8-azainosine and 8-azaadenosine

Four types of carboeyclic analogs of 8-azahypoxanthine and 8-azaadenine nucleosides have been prepared. This group of analogs is comprised of derivatives having the (±)-as-3-(hydroxy-methyl)cyclopentyl,(±)-trans-3-hydroxy-cis-4-(hydroxymethyl)cyclopentyl), (±)-trans-2-hydroxy-cis-4-(hydroxymethyl)cyclopentyl, and (±)-trans-2, trans-3-dihydroxy-cis-4-(hydroxymethyl)-cyelopentyl groups at position 3 of 3,6-dihydro-7H-v-triazolo[4,5-d]pyrimidm-7-one and of 7-amino-3H-v-triazolo[4,5-d]pyrimidine. Diazotization of (5-amino-6-chloropyrimidin-4-yl-amino)eyclopentane derivatives and acidic hydrolysis, without isolation of the resulting 7-chloro-3H-v-triazolo[4,5-d]pyrimidines yielded the 8-azahypoxanthine derivatives (III). Treatment of unpurified 7-chloro-3H-v-triazolo[4,5-d]pyrimidines with anhydrous ammonia gave the 8-azaadenine derivatives (IV). The cyclopentane analogs of 8-azaadenylic acid and of 8-aza-adenosine 3′,5′ -cyclic monophosphate were prepared from the 8-azaadenosine analog.     

Stereochemistries of electron impact induced hydrogen abstraction reactions proceeding through 6-membered transition states

The stereochemistries of nine electron-impact induced eliminations proceeding from derivatives of the cis-4-t-butyl system have been determined. The predominant cis elimination observed in every case is consistent with the substantial integrity of the cyclohexyl ring prior to fragmentation, and with a cyclic transition state for hydrogen abstraction. The stereochemistries of electron impact induced eliminations from 11 derivatives of the trans-4-t-butylcyclohexyl system exhibit a dichotomy. The predominatn trans stereochemistry observed in six electron impact induced eliminations, and the nonstereospecific electron impact induced dehydration of trans-4′-t-butylcyclohexyl-ethanol are consistent with nonconcerted elimination from a chair-like cyclohexyl ring. Conversely, the McLafferty rearrangement of trans-4′-t-butyl-cyclohexyl-2-propanone proceeds nonstereospecifically. trans-4-t-Butylcyclohexyl acetaldehyde, 2-methyl-3-(trans-4′-t-butylcyclohexyl)-1-propane and trans-4-t-butylcyclohexyl-S-methyl xanthate exhibit predominant cis McLafferty rearrangement stereochemistry. This result may be due to fragmentation through boat-like conformers in these compounds.