肼类衍生物在五元唑类杂环合成中的应用进展

简要概述了肼类衍生物的结构及反应活性,总结了近十年来肼类衍生物分别在合成五元唑类杂环如吡唑、噻唑、1,3,4-噁二唑、1,3,4-噻二唑以及三唑类化合物,及其相关的稠杂环如吡唑并某环、s-三唑[3,4-b][1,3,4]-噻二唑、s-三唑[3,4-b][1,3,4]-噻二嗪,以及含有1,2,4-三唑的稠杂环化合物等合成中的应用进展.     

Synthesis and comparative studies of carbosilane liquid crystalline dendrimers with chiral terminal mesogenic groups

A new series of carbosilane liquid crystalline (LC) dendrimers from the first to the third generations with 8, 16 and 32 chiral terminal mesogenic groups, respectively, has been synthesized. The molecular structures and purity of all new compounds were confirmed by ¹H NMR spectroscopy and GPC analysis. Data of polarization microscopy and SAX analysis demonstrated that all LC dendrimers synthesized form a chiral smectic SmC* phase at temperatures below 50 °C. It has been found that bistable electrooptical switching is observed for all dendrimers. The influence of chiral mesogenic fragment length on phase behavior and ferroelectric properties of carbosilane LC dendrimers is discussed.     

An investigation of the synthesis of chiral LCs based on the [1,2,3]-triazole ring

The design and synthesis of chiral liquid crystalline compounds based on the [1,2,3]-triazole heterocycle using the click chemistry modular approach is presented. The target compounds showed LC phases of type SmA, SmC* and helical N* (cholesteric). Mesomorphic behaviour was determined by polarizing optical microscopy and differential scanning calorimetry. Contact experiments indicated a right-handed helix for the macrostructure of the cholesteric phase.     

An investigation of the synthesis of chiral LCs based on the [1,2,3]‐triazole ring

The design and synthesis of chiral liquid crystalline compounds based on the [1,2,3]‐triazole heterocycle using the click chemistry modular approach is presented. The target compounds showed LC phases of type SmA, SmC* and helical N* (cholesteric). Mesomorphic behaviour was determined by polarizing optical microscopy and differential scanning calorimetry. Contact experiments indicated a right‐handed helix for the macrostructure of the cholesteric phase.     

Dimesogenic compounds consisting of cholesterol and azobenzene-based moieties: dependence of liquid crystal properties on spacer length and fluorination of the terminal chain

The liquid crystalline (LC) properties of two series of non-symmetric dimesogenic compounds consisting of cholesterol and azobenzene-based moieties interconnected by ω-oxyalkanoyl spacers of varying length are compared: one series (AOC-n) has an octyloxy chain attached to the azobenzene mesogen unit while the other (AOCF-n) has a perfluoroheptylmethyloxy chain. In general, compounds bearing the fluorinated alkoxy chain exhibited LC properties over a much broader temperature range than those with the alkoxy chain. In addition, the AOC-n series exhibited the chiral smectic C (SmC*), smectic A (SmA) and cholesteric (N*) phases depending on the length of the central spacer, whereas the AOCF-n series favoured the formation of only the SmA phase with the N* phase completely suppressed. Both series showed an odd-even dependence of the isotropization temperature on spacer length.     

Preliminary communication A novel class of heterocyclic liquid crystals with broad smectic C phase

A successful approach in molecular design through fusing aromatic/heterocyclic rings for broadening the smectic C (SmC) phase and the synthesis of the first heterocyclic liquid crystalline (LC) molecules containing 3,7-disubstituted quinoline with one of the widest SmC phases are reported. Their naphthalene analogues are compared. The nitrogen atom in quinoline system introduces attractive forces to aid the formation of the tilted SmC phase and the flexible chain length also influences the tilted SmC phase effectively.     

Chiral two ring compounds exhibiting antiferroelectric phases

Novel chiral two ring compounds possessing phenylethenoate moieties were synthesized and their liquid crystalline properties determined. Some of these compounds were found to exhibit SmC* γ, AF and SmC* A phases, whereas in other compounds only SmA* and SmC* phases appear. The influence of the molecular structure on the appearance of SmC* γ, AF and SmC* γ phases is discussed. The basic electro-optical properties of the homologous series of ( S )-( E )4-(1-methylheptyloxycarbonyl)phenyl 4-alkoxycinnamates, in which SmC*, SmC* γ, AF and SmC* A phases appear, were also investigated. High values of spontaneous polarization, low threshold voltages and fast switching times at room temperature were observed.     

Carbosilane liquid crystalline dendrimers with terminal chiral mesogenic groups: structure and properties

This paper presents a systematic study of two series of carbosilane liquid crystalline (LC) dendrimers from first to fifth generations bearing 8, 16, 32, 64 and 128 terminal chiral mesogenic groups, respectively. All the LC dendrimers synthesized are characterized by the same glass transition temperature around -5°C. It has been shown that the LC dendrimers of the lower generations (G-1-G-3) form a ferroelectric SmC* phase over a very broad temperature range up to about 180°C, while the LC dendrimers of the higher generations (G-4 and G-5) display a rectangular columnar mesophase (Col_r). Schemes of packing in the SmC* and Col_r mesophases formed by the LC dendrimers are suggested and discussed. Electrical measurements on the ferroelectric LC dendrimers have shown that an increase in generation number leads to a decrease in the value of the spontaneous polarization and an increase in switching time.     

Synthesis,characterisation and phase transition studies in N-(-4-ethyloxybenzylydene)-4’-alkoxyanilines

Synthesis and characterisation are carried out in N-(-4-ethyloxybenzylidene)-4?-alkoxyanilines, 2O.Om liquid crystalline (LC) compounds with m = 3, 4 and 6–10. All the compounds exhibit monovariant nematic phase except with m = 10; the LC material shows bivariant nematic-smectic-C in addition to the nematic phase. Further, the variation in density with temperature in all these seven compounds is studied. The density and thermal expansion coefficient results reveal that the phase transitions, namely isotropic to nematic and nematic to SmC, present in these compounds show first-order nature as expected and that all the parameters show characteristic change in the vicinity of the phase transformation. The results are discussed in the light of the data available on other nO.Om compounds.     

Carbosilane liquid crystalline dendrimers with terminal chiral mesogenic groups: structure and properties

This paper presents a systematic study of two series of carbosilane liquid crystalline (LC) dendrimers from first to fifth generations bearing 8, 16, 32, 64 and 128 terminal chiral mesogenic groups, respectively. All the LC dendrimers synthesized are characterized by the same glass transition temperature around -5°C. It has been shown that the LC dendrimers of the lower generations (G-1-G-3) form a ferroelectric SmC* phase over a very broad temperature range up to about 180°C, while the LC dendrimers of the higher generations (G-4 and G-5) display a rectangular columnar mesophase (Col_r). Schemes of packing in the SmC* and Col_r mesophases formed by the LC dendrimers are suggested and discussed. Electrical measurements on the ferroelectric LC dendrimers have shown that an increase in generation number leads to a decrease in the value of the spontaneous polarization and an increase in switching time.     

Oximes of five-membered heterocyclic compounds with two heteroatoms 2. Reactions and biological activity (Review)

Data on the reactions of oxazole, thiazole, pyrazole, and imidazole aldoximes, ketoximes, amidoximes, and their derivatives are reviewed. The synthesis of new heterocycles based on the oximes of five-membered heterocyclic compounds with two heteroatoms are considered separately. The principal results from investigation of the biological activity of the ethers of these oximes are also presented. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1123–1155, August, 2007.     

Synthesis and cyclization reactions with pyrazolopyrimidinyl keto esters part I. Reactivity of pyrazolopyrimidinyl β-keto ester and pyrazolopyrimidinyl α,β-unsaturated ketones

5-Acetyl-4,5-dihydro-1-phenylpyrazolo[3,4-d]pyrimidin-4-one was prepared and subjected to various chemical transformations to give novel 5-heterocyclic pyrazolopyrimidinone derivatives of expected important biological activity. Then, the latter compounds were used to obtain β-keto ester and α,β-unsaturated carbonylpyrazolopyrimidinones which were used as alternate precursors to produce new pyrazolopyrimidinones substituted with five-membered heterocycles such as pyrazole and isoxazole. The structure of these compounds was identified on the basis of their chemical behaviour as well as elemental and spectral analysis.     

Monosubstituted thermotropic ferrocenomesogens containing heterocyclic pyrazole

The synthesis and mesomorphic properties of two series of ferrocenyl derivatives, 5-[4-(4-alkoxylbenzyloxy)phenyl]-3-(4-ferrocenylphenyl)-1H-pyrazoles 1a and 3-[4-(4-ferrocenylbenzyloxy)phenyl]-5-(4-alkoxylphenyl)-1H-pyrazoles 1b are reported. Compounds 1a exhibited either nematic (N) or smectic A (SmA) phases, whereas compounds 1b formed N/SmC or SmA/SmC phases depending on the terminal carbon length. The formation of SmC phases in compounds 1b was attributed to better molecular interaction between layers since the ferrocenyl unit was remotely located one phenyl ring away from pyrazole core. In contrast, their precursors, ferrocenyl β-diketonates, were in fact non-mesogenic. A less bent shape formed by ferrocenyl pyrazoles than ferrocenyl β-diketones was believed to be responsible for the formation of observed mesophases. The crystal and molecular structure of 3-[4-(4-ferrocenylbenzyloxy)phenyl]-5-(4-hexyloxyphenyl)-1H-pyrazole (1b; n=6) was determined by means of X-ray structural analysis. It crystallizes in the triclinic space group p-1, with a=11.0725(5) Å, b=12.5514(5) Å, c=14.2085(6) Å, and Z=2. The molecular arrangement was quite consistent with the layer structure observed by powder X-ray diffractometer. The cyclic voltammogram measured for 1 and 2 (n=16) indicated that incorporation of pyrazole group hardly influenced the electrochemical behavior of the ferrocenyl moiety.     

Light-driven phase transition in a cubic-phase-forming binary system composed of 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid and an azobenzene derivative

Binary mixtures were prepared from an azobenzene derivative and a liquid-crystal (LC) compound that exhibits smectic?C (SmC) and bicontinuous cubic (Cub(bi)) LC phases. Reversible switching between the two phases in response to UV-light irradiation was observed. This light-driven SmC-to-Cub(bi) transition is the first example showing the increased dimensionality of molecular ordering with isomerization of azobenzenes (see figure).     

Synthesis and characterization of a chiral antiferroelectric series with new SmC A*-L transition

Two new chiral series with a tolane core: (S) 4-(1-methylheptyloxycarbonyl)phenyl (series IB) and (S) 4-(1-ethylheptyloxycarbonyl)phenyl (series IC) 4-alkanoyloxytolane-4'-carboxylates have been synthesized and characterized. All the compounds are mesomorphic, and most of them display the antiferroelectric SmC*A phase. The mesomorphic properties have been analysed by optical microscopy, DSC, helical pitch and electro-optical measurements and X-ray diffraction study. Series IB exhibits a very rich polymesomorphism with SmC*alpha, SmC*, SmC* F12, SmC* F11 and SmC*A phases, like the previously reported series IA, [(S) 4-(1-methylheptyloxycarbonyl)phenyl 4-alkyloxytolane-4-carboxylates]. Series IC is more interesting because it presents for the first time in antiferroelectric series the liquid-like phase (L phase) between the SmC*A and isotropic phases. Preliminary optical studies plead in favour of a helical short range structure for this new liquid-like L phase.     

Synthesis and characterization of a chiral antiferroelectric series with new SmC A*-L transition

Two new chiral series with a tolane core: (S) 4-(1-methylheptyloxycarbonyl)phenyl (series IB) and (S) 4-(1-ethylheptyloxycarbonyl)phenyl (series IC) 4-alkanoyloxytolane-4'-carboxylates have been synthesized and characterized. All the compounds are mesomorphic, and most of them display the antiferroelectric SmC*A phase. The mesomorphic properties have been analysed by optical microscopy, DSC, helical pitch and electro-optical measurements and X-ray diffraction study. Series IB exhibits a very rich polymesomorphism with SmC*alpha, SmC*, SmC* F12, SmC* F11 and SmC*A phases, like the previously reported series IA, [(S) 4-(1-methylheptyloxycarbonyl)phenyl 4-alkyloxytolane-4-carboxylates]. Series IC is more interesting because it presents for the first time in antiferroelectric series the liquid-like phase (L phase) between the SmC*A and isotropic phases. Preliminary optical studies plead in favour of a helical short range structure for this new liquid-like L phase.     

Novel mesogenic asymmetric diacylhydrazines: synthesis, mesomorphic behaviour and X-ray study

The synthesis and liquid crystalline properties of a new series of diacylhydrazine derivatives (2a-g) are reported. All compounds of series 2 exhibit a smectic C (SmC) phase. The first homologues (2a, 2b) display a monotropic SmC mesophase, whereas the highest homologues (2c-g) exhibit an enantiotropic SmC phase. The liquid crystalline properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray measurements.     

Antiferroelectric and ferrielectric liquid crystalline low molar mass materials and polymers

Novel liquid crystalline Low Molecular Mass (LMM) materials bearing two chiral lactate groups, as well as compounds of like structure to MHPOBC have been synthesized. All the LMM compounds exhibit the SmC*A (antiferroelectric) and/or SmC*gamma (ferrielectric) phases. The mesogens have been incorporated as pendant groups on polymer backbones of three different natures to prepare side chain liquid crystalline copolysiloxanes, homopolysiloxanes and homopolyacrylates. The investigation of the polymers by means of miscibility studies showed that the antiferro- and ferri-electric phases are strongly destabilized in the coposiloxanes and homopolysiloxanes, while in the homopolyacrylates a large temperature range mesophase is found to be miscible with the SmC*A phase. The physical properties of the mesophases and their stability, both for the LMM materials and the polymers, are presented and discussed.     

Influence of hydrogen bonding on phase abundance in ferroelectric liquid crystals

The synthesis and characterization of five hydrogen-bonded ferroelectric liquid crystal complexes (HBFLCs) prepared from mesogenic p-n-alkoxy benzoic acids and non-mesogenic propionic/butyric acids with different chiral centres are reported. Complementary intermolecular hydrogen bonding is confirmed through IR study. HBFLCs are found to exhibit chiral nematic (N*), smectic C* (SmC*) and smectic G* (monotropic) phases in their cooling profiles during polarizing thermal microscopy and differential scanning calorimetry. Phase coexistence regions are observed above the IN* transition. The chiral nematic to smectic C* transition is found to be of first order. The temperature variation of spontaneous polarization exhibited by these HBFLC complexes in their SmC* phase is presented. The effect of non-covalent interaction imparted by the soft hydrogen bonding in these LC complexes on enhanced or induced thermal stability of tilted LC phases is discussed.     

Synthesis and mesomorphic properties of fluoro-substituted chiral liquid crystals derived from (S)-lactic acid with alkoxyethanols

A homologous series of fluoro-substituted chiral liquid crystals derived from (S)-lactic acid and alkoxyethanols were prepared for investigation. Mesophases and their corresponding transition temperatures were identified by polarized optical microscopy and differential scanning calorimetry. The compounds exhibit a broad temperature range in the ferroelectric chiral smectic C (SmC*) phase; in particular, compounds with shorter alkyl chain lengths have an SmC* phase at ambient temperature. The physical properties of the ferroelectric SmC* phase, such as switching current, spontaneous polarization, optical tilt angle and electro-optical response, were also measured. The effects of fluoro substituent on the mesophases and physical properties of the chiral liquid crystals are discussed.