Synthesis and characterization of terminally carboxyl ethylene glycol monomethyl ethers-substituted side-chain liquid-crystalline polysiloxanes

Alkene monomers containing phenyl or biphenyl carboxylate benzoate ester based on a mesogenic group of varied lengths of carboxyl oligo (ethanediol) monomethyl ethers as the terminal were synthesized. They were grafted onto poly(methyl-hydrosiloxane) by the platinum-catalyzed hydrosilylation process. The thermal transition temperatures and mesophase textures of monomers and of polymers were characterized by using differential scanning calorimetry (DSC), x-ray diffraction, and polarized optical microscopy with a hot stage. The factors governing mesophase textures and thermal transition temperatures are discussed. © 1993 John Wiley & Sons, Inc.     

Synthesis, characterization and fluorescence studies of novel bi-phenyl based acrylate and methacrylate

4-[(1E)-3-(biphenyl-4-yl)buta-1,3-dien-1-yl]phenyl prop-2-enoate (ACH) and 4-[(1E)-3-(biphenyl-4-yl)buta-1,3-dien-1-yl]phenyl 2-methylprop-2-enoate (MCH) was synthesized from biphenyl in three steps and their structures were confirmed by elemental analysis, IR, NMR (1H, 13C, DEPT135, 1H-1H COSY, 1H-13C HSQC and 1H-13C HMBC) spectroscopic techniques. In this present study, various physicochemical characteristics we demonstrate solubility, color, absorbance and fluorescence property of novel biphenyl based acrylate and methacrylate measured in different solvents like benzene, dichloromethane, tetrahydrofuran, acetonitrile, dimethylsulfoxide and ethanol.     

Polymerizable Ester-Type Banana Liquid Crystals: A Comparative Study of Mesophase Behavior

Two families of ester-type banana monomers are presented, 1,3-phenylene bis{4-[4′-(10-undecenyloxy)benzoyloxy]benzoate}s and 1,3-phenylene bis{[4′-(10-undecenyloxy)]-1,1′-biphenyl-4-carboxylate}s, in which the nature of the substituents on the central phenyl ring and the side arms was varied. The mesophase behavior of the monomers, including B₂ and B₇ phases, was correlated with their chemical structure and was compared with that of analogous azomethine-type banana mesogens. It is also shown that the banana monomers can be incorporated into new architectures of liquid crystal polymers.     

High functionalization of 5-nitro-1H-imidazole derivatives: the TDAE approach

We report herein the synthesis of substituted 2-[4-(1,2-dimethyl-5-nitro-1H-imidazol-4-yl)phenyl]-1-arylethanols, ethyl 3-[4-(1,2-dimethyl-5-nitro-1H-imidazol-4-yl)-phenyl]-2-hydroxypropanoate and 2-[4-(1,2-dimethyl-5-nitro-1H-imidazol-4-yl)benzyl]-2-hydroxy-acenaphthylen-1(2H)-one from the reactions of 4-[4-(chloromethyl)phenyl]-1,2-dimethyl-5-nitro-1H-imidazole with various aromatic carbonyl and a-carbonyl ester derivatives using tetrakis(dimethylamino)ethylene (TDAE) methodology.     

Dependence of Mesomorphic Behaviour of Methylene‐Linked Dimers and the Stability of the NTB/NX Phase upon Choice of Mesogenic Units and Terminal Chain Length

Twelve symmetrical dimeric materials consisting of a nonamethylene (C9) spacer and either phenyl 4‐(4′‐alkylphenyl)benzoate, phenyl 4‐(4′‐alkylcyclohexyl)benzoate or phenyl 4‐(4′‐alkylbicyclohexyl)carboxylate mesogenic units were prepared and their mesogenic behaviour characterised by POM, DSC and XRD. All of the materials exhibited nematic phases with clearing points in excess of 200 °C. Four compounds were found to exhibit the twist‐bend nematic phase, with one material exhibiting a transition from the N_TB phase into an anticlinic smectic ‘X’ phase. Across all three series of compounds the length of terminal chain is seen to dictate, to some degree, the type of mesophase formed: shorter terminal chains favour nematic and N_TB mesophases, whereas longer terminal aliphatic chains were found to promote smectic phases.     

Dynamics in ferro- and antiferroelectric phases of a liquid crystal with fluorinated molecules as studied by dielectric spectroscopy

For 1-[3-fluoro-4-(1-methylheptyloxycarbonyl)phenyl]-2-[4-2,2,3,3,4,4,4-heptafluorobutoxybutoxy)biphenyl-4-yl]ethane (1F7), built of chiral molecules, results of dielectric measurements of liquid-crystalline and solid phases are presented. Rich polymorphism of liquid-crystalline (SmC*, SmC*_A and SmI*_A) phases as well as of solid (Cr1 and Cr2) phases were observed down to –130°C. At a frequency range from 0.1 Hz to 3 MHz, the relaxation processes were detected in ferroelectric SmC*, antiferroelectric SmC*_A and highly ordered SmI*_A smectic phases. The mechanism of complex dynamics (moleculear and collective) was identified with the help of the bias field. Vitrification of conformationally disordered crystal phase Cr2 was found in accordance with calorimetric observations.     

Preparation and characterization of side-chain liquid crystalline polymers containing chenodeoxycholic acid residue

A series of new side-chain liquid crystalline polymers containing chenodiol residue derived from 24-[4′-hydroxybiphenyl-4-yl-4-(allyloxy)benzoyloxy]-3α,7α-di{n-[4′-(4-ethoxybenzoyloxy)biphenyl-4-yloxy]-n-oxoalkanoyloxy}-5β-cholane was designed and prepared. The chemical structures of the monomer and polymer were confirmed by Fourier transform infrared and ¹H NMR spectra. The mesomorphic properties of monomer and polymer were investigated by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X-ray diffraction. The side-chain liquid crystalline polymers revealed wide mesophase temperature range and high thermal stability, and they showed nematic liquid crystalline phase. The influence of flexible space group length on thermal properties and specific rotation was examined.     

Synthesis,reactions, and antimicrobial evaluations of new benzo[e][1,3]thiazine derivatives

4H-Spiro[benzo[d][1,3]oxathiine-2,1′-cyclohexan]-4-one undergoes aminolysis with certain aromatic amines to give the respective 4-benzenesulfonamide, Ethyl benzoate, and 4-acetylphenyl of 4-oxospirobenzo[e][1,3]thiazine derivatives. The Schiff bases prepared by reacting Ethyl benzoate derivative 2a with aldehydes, undergoes cyclocondensation with thioglycolic acid yielding p-methoxyphenyl and 2-(thiophen-2-yl) thiazolidinone derivatives. Treatment of the benzoate derivative with hydrazine hydrate afforded the corresponding benzohydrazide derivative which upon reaction with phenyl isocyanate and phenyl isothiocyanate afforded the urea and thiourea derivatives. New pyrimidine, pyridone, and imino pyridine derivatives of 4-oxospirobenzo[e][1,3]thiazine were also successfully prepared by reacting 2b or 2c with the appropriate organic reagents. Structural elucidations for the new products were based upon compatible microanalytical and spectroscopic measurements. Besides, their biological screening indicated that they possess potent antimicrobial activity in comparison with reference drugs.     

Synthesis of condensed tetrahydroimidazo[1,2-a]quinazoline-1,5-dione derivatives

Heating of N-{2-[(R-amino)carbonyl]phenyl}prolinamides in triethyl orthoformate solution was found to give 6-R-5,6,6a,8,9,10,10a,11-octahydropyrrolo[1′,2′:3,4]imidazo[1,2-a]quinazoline-5,11-diones. Similar reaction of N-{2-[(R-amino)carbonyl]phenyl}thiazolidine-4-carboxamides afforded 6-R-5,6,6a,10,10a,11-hexahydrothiazolo[3′,4′:3,4]imidazo[1,2-a]quinazoline-5,11-diones. The relative configuration of C-6a and C-10a centres of the tetracyclic compounds obtained was assigned as trans on the basis of X-ray crystallographic study.     

An Asymmetric Synthesis of L-694,458, a Human Leukocyte Elastase Inhibitor, via Novel Enzyme Resolution of beta-Lactam Esters

A convergent synthesis of [S-(R,S)]-2-[4-[(4-methylpiperazin-1-yl)carbonyl]phenoxy]-3,3-diethyl-N-[1-[3,4-(methylenedioxy)phenyl]butyl]-4-oxo-1-azetidinecarboxamide (L-694,458, 1), a potent human leukocyte elastase inhibitor, was achieved via chiral synthesis of key intermediates: (S)-3,3-diethyl-4-[4'-[(N-methylpiperazin-1-yl)carbonylphenoxy]-2-azetidinone (2) and (R)-alpha-propylpiperonyl isocyanate (3). Synthesis of beta-lactam 2 was achieved by a novel enantioselective lipase hydrolysis of ester 5 to produce (S)-3,3-diethyl-4-(4'-carboxyphenoxy)-2-azetidinone (6) (60% yield, three cycles, 93% ee) with isolation, epimerization, and recycling of the undesired (R)-ester 5. Isocyanate 3 was prepared by chiral addition of Zn(n-Pr)(2) to piperonal (98% yield, 99.2% ee), azide displacement and reduction to (R)-alpha-propylpiperonylamine (11) (58% yield, 85% ee), crystallization as the D-pyroglutamic acid salt (92% yield, 98.2% ee), and isocyanate formation (98% yield) with phosgene.     

New 3,3′[2,2′‐oxy‐bis‐(oxazaborolidine)]‐ethylenes. Structural studies by NMR,X‐ray,and quantum chemistry methods

3,3′‐[2,2′‐Oxy‐bis‐(4S‐methyl, 5R‐phenyl‐1,3,2‐oxazaborolidine)]ethylene ( 4a ) and 3,3′‐[2, 2′‐oxy‐(4S‐methyl‐5R‐phenyl‐1,3,2‐oxazaborolidine)‐ (1,3,2‐benzoxazaborolidine)]ethylene ( 4b ) were synthesized by the reaction of N,N′‐bis‐[(1R,2S)‐norephedrine]oxalyl ( 3a ) or N,N′‐[((1R,2S)‐norephedrine, o‐hydroxyphenylamine]oxalyl ( 3b ) with BH₃‐THF. The molecular structure of these compounds was established by NMR and infrared spectroscopy. The molecular geometry for 4 was studied by means of theoretical methods, resulting in structures that were in total agreement with those obtained by spectroscopy data and X‐ray diffraction. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:513–519, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20151     

Engineering with metallo-supramolecular polymers: linear coordination polymers and networks

Here we demonstrate the synthesis of telechelics with different spacer units and different numbers of metal-complexing units, like α-methoxy-ω-(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylenoxide)₇₈ ( 1 ), bis(2,2′:6′,2″-terpyrid-4′-yl) di(ethylene glycol) ( 2 ), bis(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylene oxide)₁₈₀ ( 3 ) and tris[(2,2′:6′,2″-terpyrid-4′-yl)-oligo (ethylenoxy-)_3.33]glycerin ( 4 ) utilizing 4-chloro-2,2′:6′,2″-terpyridine. The complexation behaviour of a variety of metal-salts towards the telechelics was studied and different supramolecular architectures were investigated, such as symmetric polymeric complexes and linear coordination polymers. Furthermore, attempts have been undertaken to prepare metallo-supramolecular cross-linked systems.     

Synthesis and characterization of liquid crystalline elastomers bearing fluorinated mesogenic units and crosslinking mesogens

Several new side‐chain liquid crystalline (LC) polysiloxanes and elastomers ( IP ‐ VIP ) bearing fluorinated mesogenic units and crosslinking mesogens were synthesized by a one‐step hydrosilylation reaction with poly(methylhydrogeno)siloxane, a fluorine‐containing LC monomer 4′‐undec‐10‐enoyloxy‐biphenyl‐4‐yl 4‐fluoro‐benzoate and a crosslinking LC monomer 4′‐(4‐allyloxy‐benzoxy)‐biphenyl‐4‐yl 4‐allyloxy‐benzoate. The chemical structures and LC properties of the monomers and polymers were characterized by use of various experimental techniques such as FTIR, ¹H‐NMR, EA, TGA, DSC, POM and XRD. The effect of crosslinking mesogens on mesomorphic properties of the fluorinated LC polymers was studied as well. The obtained polymers and elastomers were soluble in many solvents such as toluene, tetrahydrofuran, chloroform, and so forth. The temperatures at which 5% weight loss occurred (T_d) were greater than 250°C for all the polymers, and the weight of residue near 600°C increased slightly with increase of the crosslinking mesogens in the fluorinated polymer systems. The samples IP , IIP , IIIP and IVP showed both smectic A and nematic phases when they were heated and cooled, but VP and VIP exhibited only a nematic mesophase. The glass transition temperature (T_g) of polymers increased slightly with increase of crosslinking mesogens in the polymer systems, but the mesophase–isotropic phase transition temperature (T_i) and smectic A–nematic mesophase transition temperature (T_S‐N) decreased slightly. It suggests that the temperature range of the mesophase became narrow with the increase of crosslinking mesogens for all the fluorinated polymers and elastomers. In XRD curves, the intensity of sharp reflections at low angle decreased with increase of crosslinking mesogens in the fluorinated polymers systems, indicating that the smectic order derived from fluorinated mesogenic units should be destroyed by introduction of more crosslinking mesogens. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and anticonvulsant activity of 3-[3-[(dimethylamino)-methyl]-5-methyl-4H-1,2,4-triazol-4-yl]-4-(o-chlorobenzoyl)pyridine

Wolff-Kishner reduction of 3-amino-4-(o-chlorobenzoyl)pyridine ( 3 ) afforded 3-amino-4-(o-chlorobenzyl)pyridine ( 5 ), which on subsequent reaction with triethyl orthoformate and then acetyl hydrazide yielded 1-acetyl-2-[N-[4-(o-chlorobenzyl)pyridin-3-yl]formimidoyl]hydrazone ( 7 ). Cyclization of hydrazone 7 gave 3-(3-methyl-4H-1,2,4-triazol-4-yl)-4-(o-chlorobenzyl)pyridine ( 8 ), which on Jones oxidation yielded 3-(3-methyl-4H-1,2,4-triazol-4-yl)-4-(o-chlorobenzyl)pyridine ( 9 ). The Mannick reaction of 3-(3-methyl-4H-l,2,4-triazol-4-yl)-4-(o-chlorobenzyl)pyridine ( 9 ) with aqueous formalin and dimethylamine hydrochloride afforded 3-[3-[(dimethylamino)methyl]-5-methyl-4H-1,2,4-triazol-4-yl]-4-(o-chlorobenzoyl)-pyridine ( 10 ). 3-[3-[(Dimethylamino)methyl]-5-methyl-4H-1,2,4-triazol-4-yl]-4-(o-chlorobenzoyl)pyridine ( 10 ) exhibited good anticonvulsant activity in the subcutaneous pentylenetetrazole anticonvulsant screen indi cating that an appropriately substituted-pyridine ring moiety can serve as a bioisostere of a chlorobenzene ring with respect to anticonvulsant activity.     

Novel Chiral,Sulfur-Containing Heteroarotinoids with Liquid Crystal Properties

Synthetic methods were developed to prepare ethyl (E)-4-[2-(3,4-dihydro-2-n-octyl-1-oxy-2H-1-benzothio-pyran-6-yl)-1-propenyl]benzoate ( 1 ) and ethyl (E)-4-[2-(3,4-dihydro-2-n-octyl-2H-1-benzothiopyran-6-yl)-1-propenyl]benzoate ( 10 ). These are the first examples of heteroarotinoids which possess properties of liquid crystals. The properties were evaluated using differential scanning calorimetry and by use of polarizing micrography. Both displayed textures which are typical of a smectic or cholesteric phase.     

Synthesis of new functionally substituted hetarylcarbamates from methyl {4-[(2<Emphasis Type="Italic">E</Emphasis>)-3-(4-methoxyphenyl)-prop-2-enoyl]phenyl}carbamate

Three-component condensation of methyl {4-[(2E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}- carbamate with ninhydrin and L-proline in methanol–water (10: 1) afforded methyl {4-[1,3-dioxo-1′- (4-methoxyphenyl)-1,1′,2′,3,5′,6′,7′,7a′-octahydrospiro[indene-2,3′-pyrrolizin]-2′-ylcarbonyl]phenyl}carbamate. Heating of methyl {4-[(2E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}carbamate with isatin and benzylamine in methanol gave methyl {4-[4′-(4-methoxyphenyl)-2-oxo-5′-phenyl-1,2-dihydrospiro[indole-3,2′-pyrrolidin]-3′-ylcarbonyl]phenyl}carbamate. The condensation of methyl {4-[(2E)-3-(4-methoxyphenyl)prop-2- enoyl]phenyl}carbamate with sarcosine and 11H-indeno[1,2-b]quinoxalin-11-one generated in situ from ninhydrin and o-phenylenediamine in boiling ethanol led to the formation of methyl {4-[4′-(4-methoxyphenyl)-1′-methyl-11,11a-dihydro-5aH-spiro[benzo[b]phenazine-6,2′-pyrrolidin]-3′-ylcarbonyl]phenyl}carbamate.     

Effect of lateral substituents on the mesomorphic properties of side-chain liquid crystalline polysiloxanes containing 4-[(S)-2-methyl-1-butoxy]phenyl 4-(alkenyloxy)benzoate side groups

The synthesis of side-chain liquid crystalline polysiloxanes containing either 4-[(S)-2-methyl-1-butoxy]phenyl 4-(alkenyloxy)benzoate or laterally fluoro-, chloro-, bromo-, and methoxy-substituted 4-[(S)-2-methyl-1-butoxy]phenyl 4-(alkenyloxy)benzoate mesogenic side groups is presented. The mesomorphic properties of the synthesized polymers have been characterized by optical polarizing microscopy, differential scanning calorimetry, and X-ray diffraction measurements. The effects of spacer length and lateral substituent on the mesomorphic properties of the obtained polymers are examined. The five polymers which contain three methylene units in the spacers show no mesophase, while the five polymers which contain eleven methylene units in the spacer display smectic mesomorphism. Among the other fifteen polymers which contain respectively four, five, or six methylene units in the spacers, those with small fluoro and chloro substituents reveal respectively an S_A phase, while those with bulky bromo and methoxy substituents show no liquid crystalline behavior. The experimental results demonstrate that introducing a bulky lateral substituent into the mesogenic core of a polymer depresses the tendency to form a mesophase. Furthermore, the technique of thermally stimulated current has been used to study the dipolar relaxation mechanisms in a side-chain liquid crystalline polysiloxane. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2793–2800, 1997     

Investigation of reactions of the organozinc reagents prepared from zinc and dialkyl dibromomalonates with the derivatives of 2-arylmethyleneindan-1,3-dione and 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-dione

Organozinc compounds prepared from dialkyl dibromomalonates and zinc react with 2-arylmethyl-eneindan-4,6-diones, 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-diones, as well as with 2-[4-(1,3-dioxoindan-2-ylidenemethyl)phenyl]methyleneindan-1,3-dione and 5-[4-(2,2-dimethyl-4,6-dioxo-1,3-dioxane-2-ylidenemethyl)phenyl]methylene-2,2-dimethyl-1,3-dioxane-4,6-diones to form dialkyl 3-aryl-1′3′-dioxaspiro(cyclopropane-2,2′-indan)-1,1-dicarboxylates, dimethyl 3-aryl-6,6-dimethyl-5,7-dioxa-4,8-dioxaspiro[2,5]octan-2,2-dicarboxylates, dialkyl 2-{4-[3,3-bis (alkoxycarbonyl)-1′,3′-dioxaspiro(cyclopropane-2,2′-indan)-1-yl]phenyl}-1′,3′-dioxaspiro[cyclopropane-2,2′-indan]-1,1-dicarboxylates, and dialkyl 2-{4-[2,2-bis(alkoxycarbonyl)-6,6′-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]oct-1-yl]phenyl}-6,6-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]octan-1,1-dicarboxylate respectively.     

Selaginellin A and B, two novel natural pigments isolated from Selaginella tamariscina

Two new unusual natural pigments were first isolated from the whole herbs of Selaginella tamariscina. The structure of selaginellin A (1) was established as (R,S)-4-[(4'-hydroxy-3-((4-hydroxyphenyl)ethynyl)biphenyl-2-yl)(4-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one and selaginellin B (2) as (R,S)-4-[(4'-methoxy-4-(methyl)-3-((4-methoxyphenyl)ethynyl)biphenyl-2-yl)(4-methoxyphenyl)methylene]-2,5-cyclohexadien-1-one, along with four known biflavonoids, amentoflavone (3), hinokiflavone (4), heveaflavone (5), and 7'-O-methylamentoflavone (6). Their chemical structures were elucidated by spectral analysis of electrospray ionization mass spectroscopy (ESI-MS), one-dimensional nuclear magnetic resonance spectroscopy (1D-NMR) and two-dimensional-nuclear magnetic resonance spectroscopy (2D-NMR) including (1)H-NMR, (13)C-NMR, distortionless enhancement by polarization transfer (DEPT) and heteronuclear multiple bond coherence (HMBC), and single-crystal X-ray diffraction techniques.     

Synthesis and characterization of fluorinated liquid-crystalline elastomers containing chiral liquid-crystalline crosslinking units

Fluorinated chiral liquid-crystalline elastomers (LCEs) were graft copolymerized by a one-step hydrosilylation reaction with polymethylhydrogenosiloxane, a fluorinated LC monomer 4-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoyloxy)phenyl 4-(undec-10-enoyloxy)benzoate (PPUB) and a chiral crosslinking LC monomer (3R,3aR,6S,6aR)-6-(undec-10-enoyloxy)hexahydrofuro[3,2-b]furan-3-yl 4′-(4-(allyloxy)benzoyloxy)biphenyl-4-carboxylate (UHAB). The chemical structure, liquid-crystalline behavior and polarization property were characterized by use of various experimental techniques. The effective crosslink density of the LCEs was characterized by swelling experiments. The thermal analysis results showed that the temperatures at which 5% weight loss occurred were greater than 250 °C for all the LCEs, and the residue weight nearby 600 °C increase with increasing chiral crosslinking components in the polymer systems. All the samples showed chiral smectic C mesophase when they were heated. The glass transition temperature and mesophase-isotropic phase transition temperature of fluorinated elastomers increased slightly with increase of chiral crosslinking mesogens in the polymer systems, but the enthalpy changes of mesophase-isotropic phase transition decreased slightly. In XRD curves, all the samples exhibited strong sharp reflections at small angles suggesting smectic layered packing arrangement. These fluorinated chiral LCEs showed 0.1–0.2 μC/cm² of spontaneous polarization with increasing chiral crosslinking component.