LC diketones: synthesis,transformations and mesomorphic properties

The synthesis and chemical transformations of various diketones into liquid crystalline compounds are discussed. The diketones were prepared by the interaction of cyclohexene with acid chlorides and benzene in the presence of aluminium chloride (Nenitzescu method) or by Friedel Crafts reaction of trans-4-alkanoyl-1-phenylcyclohexanes or trans-2-alkyl-5-phenylcyclohexanones with acid chlorides, or by the condensation of corresponding Mannich salts with 2-substituted acetoacetates or acetylacetone.     

三甲基硅化合物复合体系引发1,3-戊二烯阳离子聚合研究

研究了三甲基硅化合物 ,主要是三甲基硅酯和三甲基硅氯化物 (TMSCI)与路易斯酸所形成的复合引发体系引发聚合 ,1,3 戊二烯 (PD)的聚合反应行为 ,考察了引发体系引发PD聚合所得聚合物的产率 ,分子量及分子量分布 ,聚合反应速率和聚合反应机理等 ;研究了多种给电体———醚、酮对聚合反应的影响     

LC diketones: synthesis, transformations and mesomorphic properties

The synthesis and chemical transformations of various diketones into liquid crystalline compounds are discussed. The diketones were prepared by the interaction of cyclohexene with acid chlorides and benzene in the presence of aluminium chloride (Nenitzescu method) or by Friedel Crafts reaction of trans-4-alkanoyl-1-phenylcyclohexanes or trans-2-alkyl-5-phenylcyclohexanones with acid chlorides, or by the condensation of corresponding Mannich salts with 2-substituted acetoacetates or acetylacetone.     

Synthesis and Some Reactions of Quinoxalinecarboazides

Chlorination of ethyl(quinoxalin‐2(1H)one)‐3‐carboxylate 1 gave ethyl (2‐chloroquinoxaline)‐3‐carboxylate 2 ;thionation of 1 by P₂S₅ or 2 by thiourea yielded the same product 3 . Reaction of chloro compound 2 or thiocompound 3 with hydrazine hydrate gave pyrazolylquinoxaline 4 . The reaction of ester 1 with thiourea or hydrazine hydrate afforded pyrimido quinoxaline 5 or carbohydrazide 6 ; the reaction of 6 with carbon disulfide in basic medium followed by alkylation afforded oxadiazoloquinoxaline derivatives 7, 8a,b . Carboazide 9 was produced by reaction of 5 with nitrous acid. Compound 9 on heating in an inert solvent, with or without amines, in alcohols or hydrolysis in H₂O undergoes Curtius rearrangments to yield 10‐13 . Reaction of 13 with thiosemicarbazide gave triazoloquinoxaline 14 which on reaction with alkylhalides or hydrazine hydrate yielded 15a‐c while hydrolysis of 13 gave 3‐aminoquinoxalinone 16 which was used as an intermediate to produce 17‐20 .     

A classification of organic redox reactions and writing balanced equations for them,with special attention to heteroatoms and heterocyclic compounds

Organic redox reactions are classified either as atom transfers (balanced by inspection) or as more complex transformations (balanced by change in oxidation number, ON, by change in DOX value, by electrochemical half-reaction, or by simultaneous linear algebraic equations). Examples presented include not only involvement of hydrogen or oxygen but also extensions to halogens, nitrogen, phosphorus, and sulfur. Complex reactions are subdivided into ones which proceed (a) without change in the number of carbon atoms per molecule, (b) with fragmentation of the carbon assemblage in the starting material, or (c) with condensation of two or more molecules of organic starting materials.     

Synthesis of 6,8,9-tri- and 2,6,8,9-tetrasubstituted purines by a combination of the Suzuki cross-coupling, N-arylation, and direct C-H arylation reactions

Novel practical methodology of synthesis of a several types of di-, tri-, and tetraarylpurine derivatives by a combination of regioselective Suzuki cross-coupling reactions and/or Cu-catalyzed N-arylation with direct C-H arylations was developed. 6,8-Diaryl- and 2,6,8-triaryl-9-isopropylpurines were prepared by one or two cross-couplings of 6-chloro- or 2,6-dichloro-9-isopropylpurine with arylboronic acids followed by Pd-catalyzed C-H arylation by aryl halides to position 8. 6-Chloropurine and adenine underwent Cu-catalyzed N-arylation to position 9 with boronic acids, followed by cross-coupling with AlMe3 and/or C-H arylation to obtain 8,9-diaryl-6-methylpurines or 8,9-diaryladenines (accompanied by products of partial N-arylation of adenine in position 6). The methodology is suitable for construction of small libraries of modified purines.     

Analytical methodology for organophosphorus pesticides used in Canada

An overview of analytical methodology for the determination of organophosphate pesticides residues in foods is presented. Sample extraction is carried out with acetone followed by a dichloromethane-hexane partition. The organic extract is purified by automated gel permeation chromatography and analysed by capillary gas chromatography with flame photometric or thermionic detection. Confirmation can be carried out by a variety of chemical derivatization techniques including hydrolysis followed by reaction of the phosphate or phenol moiety, direct alkylation or trifluoracetylation. Thin-layer chromatography with enzyme inhibition detection can be used as a rapid screening technique or to confirm results obtained by gas chromatography. Liquid chromatography has not been used much for the determination of organophosphorus compounds in foods.     

ORGANOSILANE POLYMERS: SYNTHESIS AND CROSSLINKING OF FORMABLE POLYMERS CONTAINING PHENYLSILYLENE UNITS

Polysilane polymers which contain silicon hydride units in the chain were synthesized by sodium coupling of PhHSiCl_2 with R~1R~2SiCl_2 in toluene (R~1 and R~2 alkyl, aryl or aralkyl), followed by termination with a monochlorosilane and neutralization with sodium bicarbonate solution. These polymers are soluble in common solvents and can be formed into a variety of shapes by molding, casting, coating or potting. This class of polymers can be crosslinked by oxidation and irradiation, or by reaction with a multifunctional vinylsilane in th presence of platinum complexes.     

Synthesis of polydentate chalcogen-containing ligands using the system hydrazine hydrate–base

The reaction of dichlorodiethyl ether or dichlorodiethylamine hydrochloride with potassium or ethanolammonium dichalcogenides prepared in situ from elemental sulfur or selenium in the system hydrazine hydrate–alkali results in oligomeric dichalcogenides, whose further splitting at the chalcogen–chalcogen bond in the same system and subsequent alkylation affords bis(organylsulfanyl)- or bis(organylselanyl)-substituted derivatives of diethyl ether or diethylamine. Ligands with aryl substituents at the chalcogens have been prepared in 48-59% yield by splitting of diaryldichalcogenides in the system hydrazine hydrate–alkali and subsequent reaction with dichlorodiethyl ether or dichlorodiethylamine. A ditopic tetradentate ligand has been synthesized by the use of dichlorodiethylformal.     

H-Bonded complexes of adenine with Rebek imide receptors are stabilised by cation-pi interactions and destabilised by stacking with perfluoroaromatics

A series of Rebek imide receptors with naphthalene or heteroaromatic platforms attached by amide or ester linkers have been prepared from the corresponding acyl chloride or anhydride; the X-ray crystal structure of the receptor-derived anhydride reveals a supramolecular H-bonded helix formation in the crystal; the complexes of adenine bound to the receptors by Hoogsteen H-bonding are found to be stabilised by stacking with a methylquinolinium ion, but destabilised by stacking with a perfluorinated naphthalene.     

Structure investigation of multiply — twinned Ni particles by electron investigation

Nickel particles are prepared by reducing NiBr₂ in organic solvent. These Ni particles are investigated by electron diffraction. Some of them are icosahedral or decahedral. We have compared the experimental results and the theoretical patterns obtained with models composed of units with a fcc structure or with either rhombohedral or orthorhombic structure for icosahedral or decahedral particles respectively. The results show that the particles are composed of units with fcc structure.     

Synthesis of 4-halophosphaisocoumarins via halocyclization of 2-(1-alkynyl)phenylphosphonates

A series of 4-halophosphaisocoumarins were prepared with high regioselectivity in good to excellent yields under mild conditions by the reaction of 2-(1-alkynyl)phenylphosphonic acid diesters with I₂ in CHCl₃ or ICl in CH₂Cl₂, or by the reaction of 2-(1-alkynyl)phenylphosphonic acid monoesters with NBS or NCS in DMF. Whether the alkynylphosphonates could cyclize or not was affected by the substituents, reaction solvents and electrophiles. A rationale for this reaction is discussed.     

Oxonium ions as initiators for vinyl polymerizations. A reappraisal

Triethyl oxonium fluoroborate either preformed or preparedin situ by the reaction of boron trifluoride etherate with epichlorohydrin does not initiate the homo or copolymerization of vinyl monomers. Small conversions to copolymers by use of these initiators with low methyl methacrylate incorporation is ascribed to conventional vinyl copolymerizations, initiated by free boron trifluoride and/or protonic impurities in the system.     

Interactions of water-soluble polymers with small molecules I: Poly(2-diethylaminoethyl methacrylate)-orange II and ethyl orange systems

The interactions between poly(2-diethylaminoethyl methacrylate) (PDEAEMA) and orange II (OII) or ethyl orange (EO) have been examined in detail by measuring the transmittance and the specific conductance of the solutions. The mechanisms of flocculation and deflocculation have been investigated by changing the intrinsic viscosity, the degree of neutralization and alkyl groups of PDEAEMA or by adding NaCl, urea or alcohols. The complexation of PDEAEMA with dyes is completed at the same mole ratio but is not dependent on the molecular weight of PDEAEMA. OII molecules bind with PDEAEMA by electrostatic interactions, followed by flocculation through hydrogen bondings between hydroxyl groups on OII molecules bound. EO molecules first interact with PDEAEMA electrostatically in the same ways as OII, but flocculation occurs by hydrophobic interactions between ethyl groups on EO molecules bound. By further addition of dyes to the complex, OII or EO molecules already bound can interact with free OII or EO molecules newly added through hydrogen/hydrophobic interaction between OII or EO molecules. Deflocculation occurs by the electrostatic repulsion between anions of dyes bound, such as (PDEAEMA-OII)-hydrogen bonding-(OII-anions) or (PDEAEMA-EO)-hydrophobic bonding-(EO-anions) newly formed.     

Phospholidines incorporating a beta N-sulfonylaminoalcohol moiety: first observed selectivity of phosphorus heterocycle aminolysis in the presence of water

Eleven 2-oxo or 2-thioxo 3-sulfonyl 1,3,2-oxazaphospholidines were synthesized in one step by condensing P(IV) dichlorides with N-sulfonyl-ethanolamines, or -aminothexylalcohols or -ortho-aminophenols. These compounds, in contrast to all other phosphorus heterocycles studied so far, reacted easily with amines, sometimes selectively in the presence of water, leading to the corresponding amides. The results are rationalized by the involvement of the addition-elimination mechanism of phosphorylation with direct collapse of the primary zwitterionic intermediate formed by the amine attack on phosphorus.     

On the mechanism and kinetics of radical reactions of epoxyketones and epoxynitriles induced by titanocene chloride

The reactions of a series of epoxynitriles and epoxyketones induced by titanocene chloride have been studied. The kinetics of the decyanogenation of beta,gamma-epoxynitriles with Ti(III) corresponds to a radical reaction (k25 approximately 106 s-1), as demonstrated by competition experiments with H-transfer from 1,4-cyclohexadiene (1,4-CHD) or PhSH or conjugate addition to acrylonitrile. The 5-exo cyclization onto nitrile induced by Ti(III) is a radical reaction (k25 approximately 107 s-1) as seen in competition experiments with H-transfer from PhSH or the titanocene-water complex. The iminyl or alkoxyl radicals generated by 5-exo cyclization onto nitriles or ketones only undergo a reduction with Ti(III). This reaction overwhelms any alternative process, such as tandem cyclization onto alkenes or beta-scission. Iminyl radicals generated by 4-exo cyclizations onto nitriles undergo reduction with Ti(III) and beta-scission reaction in a ratio of 96:4 when the alpha-substituent is CN. Alkoxyl radicals from 4-exo cyclizations onto ketone carbonyls undergo reduction with Ti(III) and beta-scission in a ratio of 60:40 when the alpha-substituent is COOR. In nearly all the reactions studied, the role of Ti(III) is triple: a radical initiator (homolytic cleavage of oxirane), a Lewis acid (coordination to CN or C=O), and a terminator (reduction of iminyl or alkoxyl radicals).     

硬段含介晶的多嵌段共聚物的合成和研究

通过对-乙酰氧基苯甲酸或对-乙酰胺基苯甲酸和聚酯-聚醚多嵌段共聚物的硬段PET进行酸解反应,和随后的乙酰氧基或乙酰胺基,和羧基间的缩聚反应,分别合成了硬段含介晶的共聚酯-聚醚多嵌段共聚物和聚酯酰胺-聚醚多嵌段共聚物,研究了它们的热致液晶行为。     

Ligand-free highly effective iron/copper co-catalyzed formation of dimeric aryl ethers or sulfides

Highly selective coupling of diiodoarenes with phenols or phenthiols can be performed by using a low-cost, benign character and readily available Fe/Cu catalytic system in the absence of ligands. It is noteworthy that the desired dimeric aryl ethers or sulfides could be obtained in high yields by coupling between diiodoarenes and phenols, or diphenols with aryl iodides.     

Fluorescent P-Hydroxyphosphole for Peptide Labeling through P-N Bond Formation

Synthesis of fluorescent P-hydroxybinaphtylphosphole-oxide or -sulfide was achieved by trapping a binaphtyl dianion with methyl dichlorophosphite or P-(N,N-diethylamino)dichlorophosphine, followed by oxidation or sulfuration of the P-center. After saponification or acid hydrolysis, the P-hydroxyphospholes were coupled to peptides using the coupling agent BOP, under the conditions required for the synthesis in solution or on a solid support. This new method was illustrated by the labeling of the JMV2959, a potent antagonist of the Growth Hormone Secretagogue Receptor type 1a (GHS−R1a). The labeled conjugates were used to characterize GHSR ligands by competition assays, based on Fluorescence Resonance Energy Transfer (FRET). Such P-hydroxyphosphole-oxide or -sulfide constitute a promising new class of compact fluorophores with large Stokes shift, for labeling biomolecules by grafting through the phosphorus atom.     

Photo-ageing of a thermoplastic aromatic polyurethane in contact with artificial sweat

An artificial photo-ageing cell was adapted in order to study the behaviour of polymers partly immersed in artificial sweat. The goal was to select polymers and to transform them into objects that come in contact with the skin. The polymer studied in this paper is a thermoplastic aromatic polyurethane (TPU) with the following characteristics: soft, transparent, lightly yellow coloured and hypoallergenic. The ageing of this polymer was studied with or without the presence of light stabilizers, and with or without sweat. The physico-chemical changes in the TPU were analysed step by step during ageing. The differences in mass variation between the different ageing modes (with or without sweat; with or without stabilizers) provided information on the hydrolytic action of the sweat. The chemical changes that occurred around the irradiated or immersed surfaces were studied by IR-ATR spectrometry in order to characterize the photo-oxidation and hydrolytic effects as well as their coupling. The morphological modifications of the polymer were recorded by differential scanning calorimetry.