Anionic Cyclization Approach to Hexahydrobenzo[b] furan-3-one and Hexahydro-1H-3-indolone:Application to Total Syntheses of Natural Products

Hexahydrobenzo[b]furan-3-one(3) and hexahydro-1H-3-indolone (4) are potentially useful intermediates for total synthesis of natural products, such as the hexahydrobenzofuran unit (5) of avermectins and pancracine (6). Anionic cyclization approach toward (3) and (4) have been developed. Their application to the total synthesis of (5) and (6) will be presented.     

Synthesis of 6-aryl-3-cinchophenyl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles

In recent years, fused heterocycles have been found to possess many unique properties in synthesis and pharmacology. Especially, 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles derivatives have been attracting much attention of chemists and pharmacologists because of their broad-spectrum biological activities such as antibacterial¹, hypotensive and CNS depressant² activities. We have prepared some 3,6-substituted 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and found that these compounds exhibited antimacrobial, insecticidal and promote plant growth.^3-5 Cinchophen had been used widely as medicine in clinic,but has been obsolete in recent years due to its by-effect. In order to seek for other uses of cinchophen, as a continuation of our preceeding studies, we used cinchophen as the starting material to synthesize ten new 6-aryl-3-cinchophenyl-l,2,4-triazolo[3,4-b]-l,3,4-thiadiazoles 5a-j. Compound 1 was prepared by the reaction of cinchophen and ethanol in the presence of sulfuric acid. 1 then reacted with hydrazine hydrate in absolute ethanol to give 2 which yielded 3 on treatment with CS₂ and KOH. On refluxing of 3 with excess hydrazine hydrate, 4 was obtained. 4 reacted with various substituted benzoic acids in the presence of POCl₃ to afifort 5a-j.     

6,6-Di-C-alkyl-d-galactopyranoses. A new group of liquid crystalline compounds forming columnar phases [1]

The geminally C-branched 6,6-di-C-n-alkyl-d-galactopyranoses 3a-d prepared in two steps from 1,2:3,4-di-O-isopropylidene-d-galacturonic acid methylester 1 and the even numbered C₈-C₁₂-alkylmagnesium bromides, represent a new group of 'double tailed' thermotropic mesogens forming columnar supramolecular structures based on hydrogen bridged (disc-like) multimers in accordance with the hypothesis of the Praefcke group. Furthermore, the thermal behaviour of the homologous 6-O-alkyl-d-galactopyranoses 4a-e is discussed in connection with the revised model for the molecular arrangement in smectic A phases of 'single tailed' carbohydrates.     

Thermotropic biaxial nematic phases with negative optical character [1]

Two disc-shaped multialkynyl arene ethers (1 and 2) with unusual thermo-mesomorphic properties are presented. Conoscopic studies show that the nematic phases of these new low molecular weight liquid crystals are biaxial and that the sign of their biaxiality is negative. The diether 2 is the first discotic twin liquid crystal which exhibits a nematic phase.     

Synthesis and thermal properties of mesomorphic 1,1'-bis[ω-(4'-cyano-4-biphenyloxy)alkyl] ferrocenes

A new series of 1,1'-disubstituted ferrocene compounds of the type [(η⁵-C₅H₄(CH₂)_nOC₆H₄C₆H₄CN]₂Fe (3a-d, n = 5, 6, 8, 11) incorporating a variable length alkyloxy cyanobiphenyl unit has been prepared and their mesomorphic properties have been investigated. Compounds 3b, c and d exhibit a thermotropic smectic C phase and 3c also exhibits a monotropic smectic A phase over a fairly wide range near ambient temperature.     

Liquid crystalline hexa-amides and side chain polysiloxanes of azacrown [18]-N6

The hexa-4-dodecyloxybenzoyl derivative 1 of azacrown [18]-N₆ was originally reported to have a 'tubular' mesophase on the basis of its large central ring and 6-fold symmetry. Starting in the mesophase, annealing of 1 under a cover slip results in formation of a new crystalline phase that melts directly to an isotropic liquid at the temperature previously observed for the mesophase to isotropic transition. Thus the phase behaviour of 1 is kinetically controlled. The analogous hexa-3,4-bisdodecyloxybenzoyl derivative 2 of azacrown [18]-N₆ has no kinetic limitations to its phase changes and has an enantiotropic columnar liquid crystalline phase. We have synthesized side chain copolysiloxanes with a (CH₂)₁₁ spacer and 75-84 per cent by weight of the same 4-dodecyloxybenzoyl-[18]-N₆ mesogen. The polysiloxanes also display a liquid crystalline phase.     

New liquid crystal compounds ( )-4-[5-(2-Methylbutyl)-1,3-dioxan-2-yl]phenyl 4-alkoxybenzoate

New liquid crystal compounds, (+)-4-[5-(2-methylbutyl)-1,3-dioxan-2-yl] phenyl 4-alkoxybenzoates (5), were synthesized. The mesomorphic behaviour of these compounds is compared with that of (+)-4-(5-alkyl-1,3-dioxan-2-yl)-phenyl 4-(2-methylbutoxy)benzoates (6). While compounds 6 exhibited a chiral smectic C phase, the corresponding compounds 5 did not. This might mean that for the appearance of a chiral smectic C phase in these types of compounds, it is necessary that the carbonyl and the chiral groups exist at nearby positions. Transition temperatures to those isotropic state for compounds 5 were lower than those for compounds 6. This result is common in both cases of (+)-4-alkoxycarbonylphenyl-4-[5-(2-methylbutyl)-1,3-dioxan-2-yl]benzoates (7), and (+)-4-(2-methylbutoxy-carbonyl)phenyl 4-(5-alkyl-1,3-dioxan-2-yl)-benzoates (8).     

Lyotropic phase behaviour of disc-shaped tetra-palladium organyls in apolar organic solvents [1]

The lyomesomorphic behaviour in apolar organic solvents of members of two series 1 and 2 of disc-shaped palladium organyls—the syntheses of four of them are new (1d, f and 2a, e) and are described here—each carrying twelve long lipophilic chains have been studied. Their lyomesomorphism appeared to be complex and has been observed here for the first time with metal organyls. As can be seen by polarizing microscopy, most of the binary mixtures investigated here exhibit nematic properties. For two members of series 1—the chloro-bridged 1b and its bromo-analogue 1c—there is even evidence for the existence of two different nematic lyomesophases side by side showing reversible transitions between them. In ternary systems, i.e. after the addition of 2,4,7-trinitrofluorenone (TNF, a strong electron acceptor), the nematic phases are stabilized, suggesting that their mesophase structures are made up by columns with intercalated TNF molecules (charge transfer complex formation). Influences of structural features of the pallado-mesogens on the one hand and of the type of solvent on the other on the molecular self-aggregation in the observed types of lyotropic mesophase formed are discussed in detail.     

Deuterium NMR studies of inositol liquid crystals [1]

Deuterium NMR investigations are presented on members of two new mesogenic series derived from the naturally occurring stereoisomers myo- and scW/o-inositol. Tetraethers of these two series exhibit thermotropic columnar phases in which the columns are apparently formed by stacked hydrogen bonded dimers of these molecules which chemically are vicinal diols. Deuterium NMR measurements were performed on the tetraoctyl homologues 2e (a cis diol) and 3e (a trans diol) of these series. We have investigated mixtures of these diols with small amounts of benzene-d₆ as probe molecules as well as samples of the neat diol compounds deuteriated at their hydroxyl groups. The results obtained show that the mesophases of both compounds are uniaxial and align partially in a magnetic field upon slow cooling from their isotropic liquids. The alignment is with the director parallel to the field direction indicating that the anisotropic magnetic susceptibility of this mesophase is positive. The deuterium quadrupole splitting of the benzene-d₆ probe in both systems is temperature dependent and in the trans diol 3e it even changes sign. This is interpreted in terms of a model in which the benzene-d₆ probe equilibrates rapidly between two (or more) solvation sites with quadrupole splittings of opposite signs The deuterium spectra of the neat deuterium labelled cis diol 2e exhibit two different signals due to the two deuterons which are located at the axial and equatorial hydroxyl groups. This indicates that there is no fast intra- or intermolecular exchange of the hydroxyl hydrogens. The overall quadrupole splittings of the hydroxyl deuterons in this compound are highly reduced compared to their static values and this is interpreted in terms of motional modes involving both reorientation of the hydroxyl deuterons about their C-O axis and overall reorientation of the molecules (or pairs of molecules) around the columnar axes. The corresponding spectra of the neat deuteriated trans diol 3e exhibit a single spectrum indicating that both hydroxyl deuterons in this compound are equivalent, or very nearly so. Within the mesophase region the spectrum undergoes gradual changes due to the increase in the molecular mobility, but the overall motional narrowing is less than in the cis isomer 2e. Apparently due to stronger hydrogen bonding in the trans isomer 3e the precession of the hydroxyl groups is hindered and a fast molecular reorientation is only possible at high temperatures.     

Solvothermal Syntheses and Characterization of Three One-dimension Cadmium Selenidoarsenates [Ni(1,2-dap)3][As2CdSe4],[Zn(1,2-dap)3][As2CdSe4] and [Ni(en)3][As2CdSe4]

Three new cadmium selenidoarsenates,[Ni(1,2-dap)3][As2CdSe4](1)(1,2-dap=l,2-diaminopropane),[Zn( 1,2-dap)3][As2CdSe4](2) and [Ni(en)3][As2CdSe4](3)(en=ethylenediamine), were synthesized under solvothermal conditions. And they are isostnictural and monoclinic crystalls. As seen from their structures, they exhibited one-dimensional(1D) chains composed of [As2CdSe4]^2- anions and [TM(amine)3]^2+(TM=Ni,Zn;amine=1,2-dap, en) cations. Their absorption edges are 2.32, 1.84 and 2.38 eV and they show the properties of the semiconductor. These compounds were also characterized by means of single-crystal X-ray ditlraction(XRD), powder X-ray diflraction (PXRD), solid-state optical absorption spectrometry, and so on.     

Preparation of a discotic 2,4,7,9-tetraaryl-6H-dibenzo[c,e][1,2]thiazine and generation of a persistent Radical 1

6H-Dibenzo[d,e][1,2]thiazine substituted with four 3,4-dioctyloxyphenyl groups forms a room temperature discotic phase with a clearing temperature of 104°C. Oxidation of the thiazine 2b with either metal oxides (PbO₂ or AgO) or SO₂Cl₂ gave a moderately stable radical 1b (a _N = 0.95 mT, g = 2.0045). Full conversion of 2b to 1b was observed with AgO in a toluene/MeCN mixture or with SO₂Cl₂. The radical 1b was isolated in the neat form with the latter oxidant. It shows sensitivity to molecular oxygen, which hampered its purification and subsequent thermal and magnetic studies.     

Synthesis and properties of optically active 1,3-diols and their derivatives as chiral dopants for ferroelectric liquid crystals

New chiral dopants β-hydroxy ketones 1, 1,3-diols 2, 1,3-dioxanes 3 and 1,3-dioxan-2-ones 4 were designed and synthesized. Reaction of (R)-1,2-epoxyoctane with carbanions derived from 2-(4-substituted phenyl)-1,3-dithianes followed by hydrolysis of the resulting hydroxy dithianes afforded 1. Reduction of 1 gave the diols 2, which yielded 3 upon acetalization and 4 upon carbonation. The syn isomers of 2, 3, and 4 exhibited larger spontaneous polarizations, when applied as chiral dopants, than the anti isomers or hydroxy ketones 1.     

Induction of nematic cholesteric (N*) phases by charge transfer complexation of disc-shaped multiynes [1]

Based on charge transfer interactions with the (chiral) electron acceptor (-)-2-(2,4,5,7-tetranitro-9-fluorenylidenaminooxy)propionic acid ((-)-TAPA), our easily accessible disc-shaped electron rich multiynes (for example, 1 and 2) give rise to two types of cholesteric nematic phases. Thus, the binary mixture of the nematic discotic (N_D) pentakis-(4-methylphenylethynyl)phenyl hexadecyl ether (2) with (-)-TAPA exhibits its twisted variant (N*_D). Likewise, but now in a ternary mixture, the homologue 1—peripherically unsubstituted and non-mesogenic—with the two electron acceptors (-)- TAPA and 2,4,7-trinitrofluorenone—both also non-liquid crystalline—shows cholesteric nematic properties, most probably however of a columnar type (N*_C). First results concerning these charge transfer induced cholesteric-nematic properties, including phase diagrams and the helical twist of the two systems presented here, are discussed on the basis of data obtained by polarizing microscopy and differential scanning calorimetry.     

The first case of a lyotropic twisted nematic (N*) phase induced by a chiral charge transfer complex [1]

The disc-shaped tetra-palladium organyl 1 forms optically active charge transfer complexes in equimolar mixtures with the enantiomers of the π-acid electron acceptor 2, (+)- or (-)-TAPA, exhibiting lyotropic cholesteric nematic properties in apolar organic solvents. These ternary systems are the first examples in which such a lyomesophase has been induced by charge transfer interactions.     

Carbon-carbon double bond in pillar[5]arene cavity: Selective binding of cis/trans-olefin isomers

The binding behavior of pillar[5]arenes (P5As) towards a series of olefin guests ((E)-1,4-dichlorobut-2-ene (1E), (Z)-1,4-dichlorobut-2-ene (1Z), (E)-but-2-ene-1,4-diol (2E), and (Z)-but-2-ene-1,4-diol (2Z), as well as an alkyne derivative 1,4-dichlorobut-2-yne (3)) have been studied in organic solution. P5As exhibit considerable selectivities for the trans-olefin isomers (1E and 2E) over their cis-isomers (1Z and 2Z). The cis/trans-selective interactions hold the potential of utilizing P5As to separate olefin isomers.     

In situ[2 + 3] cycloaddition synthesis,crystal structures,strong SHG responses and fluorescence properties of three novel Zn coordination polymers

We report on the synthesis of two acentric and one centrosymmetric Zn metal-organic complexes with 3-tetrazolenethyl pyridine spacers obtained in situ by hydrothermal routes.X-ray diffraction structural analysis reveals that they have the same equivalent nodes but with dissimilar topologies.The two acentric frameworks[Zn(Tzmp)Cl]n(1)and([Zn(Tzmp)Br]n(2),HTzmp=3-tetrazolemethyl pyridine)are isomorphism which exhibit an acentric 3D framework with(10,3)-b net called"ths",while the centro symmetric complex([Zn(Tzmp)N3]n(3))features a distinctive 2D sheet with Shubnikov hexagonal plane net.Photo-luminescent studies suggest the ligand-field strength of coordinated negative ions(Cl^->Br^->N3^-)has ordered adjusting effects on the emission redshift.The second harmonic generation(SHG)measurement shows that compounds 1 and 2 are nonlinear optically active,with SHG responses being 2/3 and half of the standard potassium dihvdrogen phosphate(KDP),respectively.     

CO2 and photo-controlled reversible conversion of supramolecular assemblies based on water soluble pillar[5]arene and coumarin-containing guest

In this communication,a new supramolecualr amphiphile was successfully constructed based on water soluble pillar[5]arene and a unique guest which contain a CO₂ responsive tertiary amine unit and a UV responsive coumarin group.When guest molecule 1 dispersed in water,it self-assembled into sheet-like structures.Upon bubbling CO₂,1 transformed into 1 H due to the tertiary amine unit was protonated,accompany the nano-sheets transformed into vesicles.Further irradiation of 1 H with 365 nm light for 3 h,the coumarin group reacted with each other to form bola-type amphiphie 2 H.In this case,vesicles collapsed and re-assembled into nano-tubes.However,when addition of WPS into the solution of 1 H,the vesicles transformed into micelles,this is due to the formation of supramolecular amphiphile WP5&1 H.Upon irradiation of WP5&1 H with 365 nm light for 3 h,nano-ribbons observed instead of micelles in the solution.Notably,nanotubes from 2 H could also transform into nano-ribbons after adding WPS.The selfassembly process and the resultant assemblies were characterized by TEM,SEM,DLS,SAXS and NMR technologies.Due to both CO₂ and light are "green" for living organisms,we anticipated our system can offer the possibilities in "on demand" drug absorption and release.     

A New Tubular Borate Built by[B14O24(OH) 6]12- Cluster Units

Anew mixed alkali and alkaline-earth metal borate Na₄Ca₂[B₁₄O₂₂(OH)₆]·2H₂O(1) has been made under a mild solvothermal condition and characterized by single-crystal X-ray diffraction, infrared(IR) spectroscopy, UV-Vis diffuse reflectance spectroscopy, powder X-ray diffraction and thermogravimetric analysis, respectively. Compound 1 features a 1D tube based on[B₁₄O₂₄(OH)₆]^12-({B₁₄}-1) oxo-boron clusters. Such a tube built by {B₁₄}-1 units has been discovered for the first time in borate system. These tubes are arranged orderly to generate 2D layers and a further 3D supramolecular network through hydrogen bond interactions. UV-Vis diffuse reflectance spectrum reveals that compound 1 is a wide band-gap semiconductor and has potential application in UV region.     

Synthesis and cytotoxicity of 28-carboxymethoxy lupane triterpenoids. Preference of 28-O-acylation over 28-O-alkylation of betulin by ethyl bromoacetate

28-Carboxymethoxy lupane tritepenoids 3 and 4 were synthesized by alkylation of betulin with the THP protected 2-hydroxyethyl iodide followed by oxidation and reduction.Direct reaction of betulin (5) or betulone (10) with ethyl bromoacetate led to 28-O-acylation, instead of 28-O-alkylation.The targeted compounds 3 and 4 were not cytotoxic at the highest concentrationtested (75 mmol/L), suggesting that elongation of the chain length at the 28-position in both betulinic acid (1) and betulonic acid (2)was detrimental to the cytotoxicity.The acylation products 28-O-bromoacetates (8a, 8b and 11) and 28-O-methoxyacetate 13exhibited cytotoxicity against several cancer cell lines tested.     

A new series of nematic and smectic liquid crystals with negative dielectric anisotropy: the effect of terminal chain substitution on thermal and electro-optical properties

Two alkyl (1b and 1c) and four fluoroalkyl derivatives (1d-1f) of 4-arylbutyric acid (1c, 1d and 1e) and 4-arylbutanol (1b, 1f and 1g) [aryl = 2',3'-difluoro-4'-(2-(E-4-pentylcyclohexyl)ethyl)-biphenyl-1-yl] were prepared and investigated in the pure form as nematic materials (1b and 1c) and as additives to a ferroelectric liquid crystal (FLC) host (1d-1f). A comparison of 1b and 1c with the decyl analogue 1a demonstrates the effect of terminal chain modification on thermal and electro-optical properties. The substitution of the -CH₂O- (1b) or -COO- (1c) for -CH₂CH₂- in 1a destabilized the N and SmA phases or completely eliminated the smectic behaviour (1c). Dielectric analysis revealed that the chain modification increased the negative Δε, reduced elastic constant K ₁₁ and moderately decreased rotational viscosity γ₁. The temperature dependence of the key electro-optical parameters was analysed for ester 2, the methyl analogue of 1c, which exhibits a 45 K wide N phase. All four fluoroalkyl derivatives 1d-1f showed enantiotropic SmA phases and 1e also exhibited a monotropic SmC phase. Solutions of 1d-1f in a FLC host (0.2 mmol g^-1) increased the tilt angle Θ (up to 45° for 1g), reduced rotational viscosity γ₁ and the risetime τ. The most dramatic changes were observed for 1g, which contains 15 fluorine atoms.