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     

Synthesis and characterization of liquid crystalline copolymethacrylates,copolyacrylates, and copolysiloxanes containing 4-methoxy-4′-hydroxy-α-methylstilbene and 4-hydroxy-4′-methoxy-α-methylstilbene constitutional isomers as side-groups

The synthesis of methacrylates and acrylates containing 4-methoxy-4′-hydroxy-α-methylstilbene and 4-hydroxy-4′-methoxy-α-methylstilbene constitutional isomers attached to the polymerizable group through flexible spacers containing 11, 8, 6, 3, and respectively 2 methylenic units is described. The radical copolymerization of a 1/2 or 2/1 mole ratio of the two constitutional isomeric monomers led to thermotropic side-chain liquid crystalline polymers in all cases. The synthesis of copolysiloxanes based on the same constitutional isomeric mesogens as side groups, and flexible spacers containing 11, 8, 6, 5, and respectively 3 methylenic units is also described. All polymers were characterized by differential scanning calorimetry and optical polarization microscopy. The polymers containing 11 methylenic units in the spacer exhibit S_c mesomorphism, while the other polymers are nematic. Copolymethacrylates do not undergo side-chain crystallization. Only the copolyacrylate containing 11 methylenic units in the spacer exhibits side-chain crystallization. All the copolysiloxanes display side-chain crystallization. The number of melting transitions seen for these polymers decreases with increasing spacer length. Copolysiloxanes containing dissimilar spacer length were also prepared. Only the copolymer synthesized with highly dissimilar spacer lengths, i.e., containing 3 and 11 methylenic units, does not undergo side-chain crystallization. These results have demonstrated that while the type of mesophase is dictated only by the spacer length, the degree of decoupling of the motion of the side-groups from the motion of the main chain is strongly dependent on the nature of the polymer backbone. For the same mesogenic unit and spacer length, the thermal stability of the mesophase is also dictated by the nature of the polymer backbone. The use of constitutional isomers of mesogenic units as side groups in liquid crystalline polymers provides at least qualitative information on the degree of decoupling of the side groups from the polymer main chain.     

Metallorganic side group liquid crystalline polymers containing pi-allylpalladium(II) groups

The preparation and phase properties of some LC pi-allyl and pi-crotyl Pd(II) side group metallorganic polymers and some related salicylaldiminates are described. The LC acrylate functionalized monomers are easily prepared, but their use to obtain the corresponding polymers by radical reaction failed because extensive decomposition of the complexes occurs with the formation of Pd metal. The synthesis of the metallated polymers was therefore performed by reacting the dimeric chloro-bridged organometallic pi-allyl or pi-crotyl Pd(II) complexes with the appropriate ligand polymer which is prepared without difficulties. The organometallic polymers show a nematic mesophase, while the ligand polymer exhibits a smectic A or C phase. Both metallated low molecular mass model compounds and the polymers give stable mesophases, although at lower temperatures compared with the parent ligand compounds.     

Isolierung von (2S, 4S)-(+)-γ-Hydroxynorvalin und (2S, 4R)-(−)-γ-Hydroxynorvalin aus Boletus satanas Lenz

We have isolated from the carpophores of Boletus satanas Lenz (Basidiomycetae) (2S,4S)-(+)-γ-hydroxynorvaline ( 1 ) and (2S,4R)-(?)-γ-hydroxynorvaline ( 2 ). The chirality of each diastereomer has been determined by chemical synthesis starting from optically active precursors and by application of different chiroptical methods. Gaschromatographic separation of the derived diastereomeric N-[(S)-α-methoxypropionyl]-lactones reveals that the optical purity of natural 2 is 88% whereas 1 exists as a partial racemate: (2S,4S): (2R,4R) = 3:2. Muscarine could not be detected in the carpophores of B. satanas, contrary to some literature data but basic substances of unknown structure are present in low concentration.     

Ind-N-alkylation of rutaecarpine and synthesis of two novel related heterocyclic ring systems: Indolo[1′,2′:3,4]pyrazo[1,2-α]quinazoline and indolo[1′,2′:3,4] [1,4] diazepino[ 1,2-α]quinazoline

The failure to obtain the N-(13)alkylrutaecarpines ( 1d,e,f ) by heating rutaecarpine ( 1a ) with neat alkyl halides at 120° is discussed in comparison with the facile reaction with methyl iodide. In contrast, with alkyl halide-potassium carbonate in acetone, the corresponding N-(13)alkyl-rutaeearpines ( 1d-l ) are obtained in good yield. By use of 1,3-diiodopropane and 1,2-dibromo-ethane, this reaction provides a facile route to 12a and 13 which are derivatives of the heretofore unknown indolo[1,2′:3,4]pyrazo[1,2-α]quinazoline and indolo[1,2 :3,4][1,4]diazepino[1,2-α]quinazoline ring systems.     

Some reactions of 5-methyl-11H-isoindolo[2,1-α] benzimidazolium salts

5-Methyl-11H-isoindolo[2,1-α]benzirnidazolium halide (IV), obtained by direct quaternization of the precursor III, underwent facile condensation reactions at its 11-methylene group similar to those of 11H-isoindolo[1,2-b]benzothiazolium cation II. Although the treatment of II with alkali regenerated its precursor I, treatment of IV with alkali caused ring opening to a phthalimidine. Attempted thermal cyclization of 2-(alkylaminophenyl)phthalimidines, e.g., VII, resulted in dealkylation to produce III.     

Side-chain liquid crystalline polymers: The synthesis and characterization of poly[4-nitrothiophenyl-4-(ω-methacryloyl oxyalkyloxy)] benzoate

A new series of sulfur-containing side-chain liquid crystalline polymer is described. Mesomorphic side chains with methylene spacers of different lengths have been synthesized, and their structures were identified by nuclear magnetic resonance, infrared and mass spectrometry. The liquid crystalline nature of the polymers was characterized by microscopy and differential scanning calorimetry.     

Polyazasteroids II.. 1,2,4-Triazolol[3′,4′:2,3]pyrimido[4,5-c]quinolin- 11(12H)ones,imidazo[2′,1′:2,3]pyrimido[4,5-c]quinolin-11(12H)ones and 2,3-dihydroimidazo[2′,1′:2,3] pyrimido[4,5-c]quinolin-11(12H)ones

Starting with 2-substituted quinoline-3,4-dicarboxylic acids, a series of substituted 1,2,3,4-tetrahydropyrimido[4,5-c]quinolinone-3-thiones were obtained. The latter compounds were converted to the three novel polyazasteroid series: 1,2,4-Triazolo[3′,4′:2,3]pyrimido[4,5-c]-quinolin-11(12H)ones, imidazo[2′,1′:2,3]pyrimido[4,5c]quinolin-11(12H)ones and 2,3-dihydroimidazo[2′,1′:2,3]pyrimido[4,5-c]quinolin-11(12H)ones. The intermediate 3-hydrazino-1,2-dihydropyrimido[4,5-c]quinolinones and nitrous acid gave the 3-azido derivatives rather than the tetrazolo compounds.     

5-(α-Fluorovinyl)tryptamines and 5-(α-Fluorovinyl)-3-(N-methyl-1′,2′,5′,6′,-tetrahydropyridin-3′- and -4′-yl)indoles—5-(α-Fluorovinyl)tryptamines

5-(α-Fluorovinyl)tryptamines 4a, 4b and 5-(α-fluorovinyl)-3-(N-methyl-1′,2′,5′,6′-tetrahydropyridin-3′- and -4′-yl) indoles 5a, 5b were synthesized using 5-(α-fluorovinyl)indole ( 7 ). The target compounds are bioisosteres of 5-carboxyamido substituted tryptamines and their tetrahydropyridyl analogs.     

Phthalocyanine polymers. I. Poly[2,2′-(4,4′,4″-,4‴-metal phthalocyanino)-5,5′-bibenzimidazoles] as new high temperature resistant polymers

A novel class of poly(metal phthalocyanino) benzimidazoles were prepared by the condensation reaction between metal (Cu, Co, and Zn), 4,4′,4″,4?-tetracarboxyphthalocyanine, and 3,3′-diaminobenzidine. The reaction was investigated by melt and solution condensation methods. These polymers showed excellent thermal and thermooxidative stability and are noteworthy for their high char yield (86–90%) at 800°C in an anerobic atmosphere. Elemental analyses, spectra, and TGA studies were used to characterize these materials. Isothermal gravimetric analyses were carried out to determine their long-term thermal stability.     

Darstellung,Eigenschaften und Kristallstruktur von [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]acetylacetonatopalladium(II)

Synthesis, Properties, and Structure of [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]-palladium(II) Acetylacetonate The reaction of Di-μ-chloro-bis[2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) with Thallium(I) acetylacetonate yields [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) acetylacetonate. The complex crystallizes monoclinic in the space group P2₁/n with the lattice constants a = 1302.4(3), b = 836.0(2), c = 1341.3(3) pm, β = 93.69(3)°. Pd has a squareplanar coordination by two O atoms of acetylacetonate, the N atom of the imidazole ring, and the C atom of the phenyl group. I.r., n.m.r., and mass spectra are reported.     

Synthesis and characterization of liquid crystalline polymethacrylates,polyacrylates, and polysiloxanes containing 4-methoxy-4′-hydroxy-α-methylstilbene-based mesogenic groups

The synthesis and characterization of polymethacrylates and polyacrylates containing 4-methoxy-4′-hydroxy-α-methylstilbene side groups attached either directly or through flexible spacers containing eleven, eight, six, three, and respectively two methylenic units, and of the polysiloxanes containing the same mesogenic group connected through flexible spacers containing eleven, eight, six, and respectively three methylenic units are described. All polymers exhibit thermotropic liquid crystallinity. The nature of the mesophase is determined by the spacer length. However, the nature of the polymer backbone determines the thermal stability of the mesophase. That is, for the same spacer length and similar polymer molecular weight, the most flexible polymer backbone leads to the highest isotropization temperature.     

Isozeaxanthine: Chiralität und enantioselektive Synthese von (4R,4′R)-Isozeaxanthin ((−)-(4R, 4′R)-β, β-Carotin-4,4′-diol)

Isozeaxanthin: Chirality and Enantioselective Synthesis of (4R,4′R)-Isozeaxanthin ((?)-(4R,4′R)-β, β-Carotin-4,4′-diol) The absolute configuration of optically active isozeaxanthin was established by synthesis using (?)-(R)-4-hydroxy-β-ionon ( 2 ) [18] as starting material.     

Separation of (3R, 3′ R)-, (3R, 3′ S; meso)-, (3S, 3′ S)- Zeaxanthin, (3R, 3′ R, 6′ R)-, (3R, 3′ S, 6′ S)- and (3S, 3′ S, 6′ S)-Lutein via the dicarbamates of (S)-(+)-α-(1-naphthyl) ethyl isocyanate

A method is described for the qualitative and quantitative determination of configurational isomers of zeaxanthin (=3,3′ -dihydroxy-β, β -carotene) and lutein (=3,3′ -dihydroxy-α -cartotene). It is based on the reaction of these zeaxathin and lutein isomers with (S)-(+)-α-(1-naphthyl) ethyl isocyanate to afford diastereomeric dicarbamates, which are analyzed by HPLC.