Synthesis and mesomorphic properties of four-ring liquid crystals containing 2,3-difluorophenyl and 1,3-dioxane units

Two series of novel liquid crystalline materials were synthesized: 2-(2,3-difluoro-4-alkoxyphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (A _m-n and 2-(2,3-difluoro-4-alkylphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (B _m-n ). Their mesmorphic properties were characterized by polarizing optical microscopy and differential scanning calorimetry. All these compounds exhibit broad mesomorphic phases, and most of them show wide smectic C phases and the phase sequence Cr-SmC-SmA-N-I. The relationship between properties and chemical structures is discussed in detail.     

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).     

Crystal structures of ferro- and antiferroelectric mesogens with a 1-methylalkoxycarbonyl group

Crystal structures have been determined for 4-[(S)-1-methylpentyloxycarbonyl]phenyl, 4-([S)-1-methylhexyloxycarbonyl]phenyl 4'-octyloxybiphenyl-4-carboxylates (1 and 2, respectively) and (R)-1-methylheptyl 4-(4'-octyloxybiphenyl-4-yloxymethylene)benzoate (3), which have S_CA*, S_C* and S_CA* phases, respectively. All the crystals have a common packing mode with the previously determined structure of 4-(1-methylheptyloxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC). Each crystal forms a smectic-like layer structure composed of largely bent molecules with the long alkyl chain of the chiral group almost perpendicular to the core moiety. Differential scanning calorimetry showed that the crystals of 1, 2, and MHPOBC, which have a carbonyloxy group as the central linkage between the biphenyl and phenylene moieties, transform to higher temperature solid phases in a similar temperature range (around 60°C). For 3, which has an oxymethylene linkage between the biphenyl and phenylene moieties, three kinds of solids were distinguished.     

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.     

Competition between micro-segregation and anti-parallel alignment of an amphiphilic rod-like liquid crystal

Recently, we reported that a rod-like molecule, 4-[4-(7-hydroxyheptyloxy)phenyl]-1-(4-hexylphenyl)-2,3-difluorobenzene, exhibited a nematic phase with a layered structure and smectic C phases consisting of three states. We prepared a homologous series of the rod-like molecules in which a 2,3-difluoro-1,4-diphenylbenzene unit and a hydroxyl unit are connected via a flexible methylene spacer. We investigated their physical properties using polarised optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Although they showed nematic, smectic A and smectic C phases, the phase structures were found to depend on the flexible spacer length. Those compounds possessing a shorter spacer length than a heptyl unit exhibited bilayered smectic A and smectic C phases, whereas those possessing a longer spacer length than a heptyl unit showed conventional monolayered smectic A and smectic C phases. A nematic phase with a smectic-like layer ordering was observed for the compound possessing an octyl unit. The structure–property relations of the amphiphilic compounds are discussed.     

Synthesis of fluorinated 2,6-heptanediones and 2-oxa-6- azabicyclo[2.2.2]octanes from 1,4-dihydropyridines

Electrophilic fluorination of Hantzsch-type 1,4-dihydropyridines with Selectfluor^® led to the formation of new fluorinated 2,6-heptanediones - dialkyl 2,4-diacetyl-2,4-difluoro-3-phenylpentanedioates. Novel 2,6-heptanedione derivatives in reaction with hydrazine hydrate easily form 6-amino-4,7-difluoro-3-hydroxy-1,3-dimethyl-5-oxo-8-phenyl-2-oxa-6-azabicyclo[2.2.2]octanes instead of the corresponding diazepine derivatives. The obtained 2-оxa-6-azabicyclo[2,2,2]octanes are thermally stable at the temperatures below 50°С. At higher temperatures rearrangement of 2-oxa-6-azabicyclo[2,2,2]octanes offers new fluorine-containing pyrazolinone derivatives - alkyl esters of 2-fluoro-2-((4-fluoro-3-methyl-5-oxo-4,5-dihydro-1H-pyrazol-4-yl)(phenyl)methyl)-3-oxobutanoates.     

New liquid crystalline cyclohexene and cyclohexane derivatives and compositions based upon them

The synthesis and chemical transformations of 3,6-disubstituted cyclohex-2-enones into new liquid crystalline cyclohexene and cyclohexane derivatives are discussed. 3,6-Disubstituted cyclohex-2-enones have been synthesized by the condensation of appropriate 2-bromoethyl ketones or Mannich salts with 2-[2-( trans -4-alkylcyclohexyl)ethyl]acetoacetic or 2-[2-(4-substituted phenyl)ethyl]acetoacetic esters.     

New liquid crystalline cyclohexene and cyclohexane derivatives and compositions based upon them

The synthesis and chemical transformations of 3,6-disubstituted cyclohex-2-enones into new liquid crystalline cyclohexene and cyclohexane derivatives are discussed. 3,6-Disubstituted cyclohex-2-enones have been synthesized by the condensation of appropriate 2-bromoethyl ketones or Mannich salts with 2-[2-(trans -4-alkylcyclohexyl)ethyl]acetoacetic or 2-[2-(4-substituted phenyl)ethyl]acetoacetic esters.     

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.     

Cyclopropanation of 5-(allyloxymethyl)- and 5-(methallyloxymethyl)-5-ethyl-1,3-dioxanes with methyl diazoacetate

Reactions of 5-(allyloxymethyl)- and 5-(methallyloxymethyl)-5-ethyl-1,3-dioxanes with methyl diazoacetate catalyzed by Rh₂(OAc)₄ or Cu(OTf)₂ in the presence of [bmim]⁺Cl⁻, [bmim]⁺BF₄ ⁻, and [bmim]⁺PF₆ ⁻ proceed regioselectively at the C=C bond and lead to the formation of the corresponding cyclopropane-containing 1,3-dioxanes in yields up to 62%.     

A NOVEL SYNTHESIS OF 2-SUBSTITUTED-4H-THIENO [2,3-d][1,3] OXAZIN-4-ONE AND 2,3-DISUBSTITUTED THIENO [2,3-d]PYRIMIDIN-4(3H)-ONE DERIVATIVES

Abstract

The synthesis of acetic 2-{[1-methyl-2-(4-oxo-5,6,7,8-tetrahydro-4H-benzo [4,5]-thieno [2,3-d] [1,3-oxazin-2-yl)ethylidene]amino}-4,5,6,7-tetrahydrohenzo[b]thiophene ?3-carboxylic acid anhydride 5 and 2-(oxopropyl)-5,6,7,8-tetrahydro-4H-benzo-[4,5] thieno[2,3-d][1,3]oxazin-4-one 7, has been achieved in three steps from ethyl 2-amino-4,5,6,7-tetrahydrobenzo(b]thiophene-3-carboxlate 1 via the reaction with ethyl acetoacetate followed by hydrolysis and acetic anhydride-induced cyclization. The 2-substituent in compound 5 has two functional groups i.e. active methylene and acid anhydride which are suitably located for intramolecular transformation. Thermal and/or base catalyzed intramolecular cyclization of 5 afforded 2-(4-acetoxy-(hydroxyl)-2-methyl-5,6,7,8-tetrahydrobenzo[4,5] thieno[2,3-b]pyridin-3-yl)-5,6,7,8- tetrahydro-4H-benzo[4,5]thieno[2,3-d] [1,3]oxazin-4-one 10 and 9 respectively. Treatment of 5 with hydrazine hydrate, aromatic and/or heterocyclic amines induced the same intramolecular cyclization with a concomitant oxazine-pyrimidine interconversion to give 3-amino(aryl or heteryl)-2-(4-hydroxy-5,6,7,8-tetrdhydrobenzo-[4,5]thieno[2,3-b]pyridin-3-yl)-3,4,5,6,7,8-hexahydrobenzo[4,5] thieno[2,3-d] pyrimid in-4-one 11–14 respectively.     

Synthesis and characterization of low molecular mass luminescent liquid crystalline materials with 1,3,4-oxadiazole units

The synthesis, and liquid crystalline and photophysical properties of luminescent liquid crystalline compounds based on 1,3-bis[5-(4-alkoxyphenyl)-1,3,4-oxadiazole-2-yl]benzene (two-fold symmetry) I and 1,3,5-tris[5-(4-alkoxyphenyl)-1,3,4-oxadiazole-2-yl]benzene II (three-fold symmetry) are described. The mesophases were characterized using polarizing optical microscopy and differential scanning calorimetry. In addition, all compounds showed blue fluorescence with emission maxima between 366 and 382 nm, and good quantum yields of photoluminescence (Φ_PL = 45%).     

Hetero-diels–alder reaction of 5-ylidene-4-sulfanylidene-1,3-thiazolidin-2-ones with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-bis(methoxycarbonyl)-1,4-benzoquinone diimine

Hetero-Diels–Alder reaction of 5-(propan-2-ylidene)-4-sulfanylidene-1,3-thiazolidin-2-one with N,N′-bis(methoxycarbonyl)-1,4-benzoquinone diimine in boiling toluene afforded 87% of dimethyl 9,9-dimethyl-2-oxo-8a,9-dihydro-2H-thiochromeno[2,3-d][1,3]thiazole-5,8(3H,4aH)-diylidenedicarbamate. Analogous reactions of 5-benzylidene-, 5-{[4-(dimethylamino)phenyl]methylidene}-, and 5-[(2-hydroxyphenyl)-methylidene]-4-sulfanylidene-1,3-thiazolidin-2-ones led to the formation of the corresponding dimethyl 9-aryl-2-oxo-3,9-dihydro-2H-thiochromeno[2,3-d][1,3]thiazole-5,8-diyldicarbamates in 64–82% yield.     

One-pot synthesis of dual-state emission (DSE) luminogens containing the V-shape furo[2,3-b]furan scaffold

To discover novel fluoro p hores of solution and solid dual-state emission(DSE) materials,unique V-shape furo[2,3-b]furans have been designed and synthesized by a one-pot method for the first time and their photoluminescent properties have been explored in benzene,THF,DMF and DMSO,as well as in the solid state.As the best example,2,5-bis(4-(9 H-carbazol-9-yl)phenyl)-6 a-amino-3 a,6 a-dihydrofuro[2,3-b]furan-3,3 a,4-trica rbonitrile(3 g) exhibited solution and solid DSE properties in THF,benzene,and in the solid state with quantum yields of 55%,92%,and 45%,respectively.     

Five-Membered 2,3-Dioxo Heterocycles: XLV. Thermolysis of 5-Aryl-4-phenyl-2,3-dihydrofuran-2,3-diones in the Absence of Other Partners and in the Presence of Carbonyl Compounds

Aroyl(phenyl)ketenes generated by thermolysis of 5-aryl-4-phenyl-2,3-dihydrofuran-2,3-diones undergo [4+2]-cyclodimerization to 3-aroyl-6-aryl-3,5-diphenyl-3,4-dihydro-2H-pyran-2,4-diones. Heating of the latter leads to rearrangement with formation of 4-aroyloxy-6-aryl-3,5-diphenyl-2H-pyran-2-ones. Thermolysis of 5-aryl-4-phenyl-2,3-dihydrofuran-2,3-diones in the presence of carbonyl compounds yields 6-aryl-5-phenyl-4H-1,3-dioxin-4-ones.     

Efficient Syntheses of New 2,2′-Disubstituted-2,3-dihydrofuran Derivatives and Natural Polyketide Analogues

Efficient syntheses of new 2,2′-disubstituted-2,3-dihydrofuran(5H)-4-one,spiro{benzofuran-2,2′-bicyclo[2.2.1]heptan}-4(5H)-one derivatives, and natural polyketide analogues have been achieved via the oxidative [3 + 2] cycloaddition of 1,3-dicarbonyl compounds with monoterpenes myrcene, camphene, and natural phenyl propenes, namely anethole and safrole respectively. Interestingly, the reaction of isoprene and myrcene with 1,3-dicarbonyl compounds yielded 2,2-disubstituted tetrahydrobenzofuran-4(5H)-one derivatives at room temperature. Thus, several substituted 2,3-dihydrofuran derivatives (3a–3h) with potential biological activity have been synthesized.     

Four unit linking groups III. Liquid crystals of negative dielectric anisotropy

A series of 1-n-alkoxy-2,3-difluoro-4-[3-(trans-4-pentylcyclohexyl)propyloxy]-benzenes has been synthesized. Several homologues exhibit an enantiotropic nematic phase of moderately strong negative dielectric anisotropy (Δε ≈ 5) at or just above room temperature. An analogous series of three-ring diethers also including some (E)-3-allyloxy derivatives possesses enantiotropic, wide range nematic phases also of moderately strong negative dielectric anisotropy, but at elevated temperatures. The synthesis and liquid crystal transition temperatures of these 2,3-difluoroquinone derivatives are described and comparisons are made with the transition temperatures of the corresponding materials incorporating standard central linkages (-, C₂H₄, CH₂O and COO).     

Regioselective oxidative coupling of 4-hydroxystilbenes: synthesis of resveratrol and epsilon-viniferin (E)-dehydrodimers

Treatment of 5-[2-(4-hydroxyphenyl)vinyl]benzene-1,3-diol (resveratrol) with an equimolar amount of silver(I) acetate in dry MeOH at 50 degrees C for 1 h followed by chromatographic purification with a short silica gel column allowed the isolation of its (E)-dehydrodimer, 5-[5-[2-(3,5-dihydroxyphenyl)vinyl]-2-(4-hydroxyphenyl)-2,3-dihydrobenzofuran-3-yl]benzene-1,3-diol, as a racemic mixture in high yield. The present method was applicable to the oxidative dimerization of 4-hydroxystilbenes such as trans-styrylphenol and 5-[6-hydroxy-2-(4-hydroxyphenyl)-4-[2-(4-hydroxyphenyl)vinyl]-2,3-dihydrobenzofuran-3-yl]benzene-1,3-diol (epsilon-viniferin) leading to the corresponding 2-(4-hydroxyphenyl)-2,3-dihydrobenzofurans possessing various types of biological activities.     

Synthesis of new pyrazolothiazole derivatives from 4-thiazolidinones

The synthesis of new 2,3,5,6-aryl substituted tetrahydro-2H-pyrazolo[3,4-d]- thiazoles 4a-j as potential biologically active compounds by the cyclocondensation of phenyl hydrazine with new 5-arylidene derivatives 2a-j of 2,3-disubstituted-1,3- thiazolidin-4-ones 1a-e is reported.     

Five-Membered 2,3-Dioxo Heterocycles: XLVII. Reaction of 5-Aryl-4-phenyl-2,3-dihydrofuran-2,3-diones with Compounds Containing C = N and C≡N Bonds

Thermal decarbonylation of 5-aryl-4-phenyl-2,3-dihydrofuran-2,3-diones gives rise to intermediate aroyl(phenyl)ketenes which react with nonactivated Schiff bases, N,N'-dicyclohexylcarbodiimide, and p-di-methylaminobenzonitrile according to the [4 + 2]-cycloaddition pattern with formation of 6-aryl-5-phenyl-4H-1,3-oxazin-4-ones. Reactions of 5-aryl-4-phenyl-2,3-dihydrofuran-2,3-diones with activated Schiff bases at a temperature below the thermolysis temperature lead to 4-aroyl-4-phenyltetrahydropyrrole-2,3-diones.