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Showing papers on "Substituent published in 2000"


Journal ArticleDOI
TL;DR: In this article, the results obtained from the oxidation of the aminoazobenzene dye AO52 by the UV/H2O2, UV/TiO2 and VIS/Ti2 systems are presented.
Abstract: This paper presents the results obtained from the oxidation of the aminoazobenzene dye AO52 by the UV/H2O2, UV/TiO2 and VIS/TiO2 systems. In the former case, we investigated the formation of first by-products by means of GC/MS, HPLC and 1H NMR. spectroscopy. We conclude that hydroxyl radicals are added to aromatic rings in the ipso position with respect to the sulfonate group or to the azo-linkage-bearing carbon. The reaction of the inorganic radical with the N,N-dimethylamino substituent, leading to demethylation, adds to the multiplicity of the possible pathways. Degradation by the UV/TiO2 system is pH dependent. Whereas hydroxyl radicals are the main oxidative agent in neutral and alkaline solutions, positive hole-induced oxidation competes with the reduction of the protonated dye molecules in acid media. Moreover, FTIR spectroscopy of AO52/TiO2 wafers provided an insight to the nature of the photoproducts. This process is very efficient since only ultimate breakdown products, i.e. aliphatic acids and inorganic salts, are detected. Similar results were obtained using visible light as the irradiation source in the case of wafers whereas in heterogeneous solutions, the dye seems to be resistant to degradation.

428 citations


Journal ArticleDOI
TL;DR: A series of bis(imino)pyridyliron and -cobalt complexes with at least one small ortho substituent, as well as Ar=biphenyl and Ar=naphthyl, has been synthesized as mentioned in this paper.
Abstract: A series of bis(imino)pyridyliron and -cobalt complexes [[2,6-(CR=NAr)2C5H3N]MX2] (R=H, Me; M=Fe, Co; X=Cl, Br) 8-16 containing imino-aryl rings (Ar) with at least one small ortho substituent, as well as Ar=biphenyl and Ar=naphthyl, has been synthesised. Crystallographic analyses of complexes 9 (Ar = 2,3-dimethylphenyl), 13 and 14 (Ar= biphenyl; X= Cl or Br, respectively) reveal a distorted trigonal-bipyramidal geometry in the solid state. These complexes, in combination with methyl aluminoxane (MAO), are active catalysts for the oligomerisation of ethylene, yielding >99% linear alpha-olefin mixtures that follow a Schulz-Flory distribution. Iron ketimine (R = Me) precatalysts give the highest activities and a greater alpha-value than their aldimine (R = H) analogues. Cobalt precatalysts follow a similar trend, though their activities are almost two orders of magnitude lower than those of the corresponding iron catalysts. Ethylene pressure studies on cobalt precatalyst 15 reveal a first-order dependence on ethylene for both the rate of propagation and the rate of chain transfer, and a pressure independence of the alpha value.

335 citations


Journal ArticleDOI
TL;DR: In this article, the capacity of organotrialkoxysilanes to form gels through the sol−gel process was examined and gels were obtained from the sol-gel polymerization of the monomers with different organic groups.
Abstract: Silsesquioxanes are a family of siloxane network polymers that have become important as vehicles for introducing organic functionalities into sol−gel materials. However, there has not been a systematic study of the capacity of organotrialkoxysilanes to form gels through the sol−gel process. In this study, we examined the sol−gel chemistry of organotrialkoxysilanes (RSi(OR‘)3) with different organic groups (R = H, Me, Et, Pr, i-Pr, n-Bu, i-Bu, t-Bu, hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, vinyl, phenyl, benzyl, phenethyl, chloromethyl, chloromethylphenyl, and tridecafluoro-1,1,2,2-tetrahydrooctyl) with methoxide or ethoxide substituents on silicon, at varying monomer concentrations, and under acidic, neutral, and basic conditions. Gels were obtained from the sol−gel polymerization of the monomers with R‘ = Me and R = H, Me, vinyl, chloromethyl, chloromethylphenyl, hexadecyl, and octadecyl and R‘ = Et and R = H, Me, Et, chloromethyl, vinyl, dodecyl, hexadecyl, and octadecyl. Formatio...

280 citations


Journal ArticleDOI
TL;DR: In this paper, a practical method for the synthesis of p-tert-butylthiacalix[4]arene (TC4A), in which the methylene bridges of C4A are replaced by epithio groups, is presented by heating a mixture of ptert butylphenol, elemental sulfur S8, and NaOH as a base catalyst in tetraethylene glycol dimethyl ether.

233 citations


Journal ArticleDOI
TL;DR: It can be concluded that the redox step (k33) is not the rate-determining step of the reaction mechanism and the monophenols are converted into diphenols, but the order of specificities towards monophenol is different to that of o-diphenols.
Abstract: This paper reports a quantitative study of the effect of ring substituents in the 1-position of the aromatic ring on the rate of monophenol hydroxylation and o-diphenol oxidation catalyzed by tyrosinase. A possible correlation between the electron density of the carbon atom supporting the oxygen from the monophenolic hydroxyl group and the V Mmax values for each monophenol was found. In the case of o-diphenols the same effect was observed but the size of the side-chain became very important. NMR studies on the monophenols justified the sequence of the V Mmax values obtained. As regards the o-diphenols, on the other hand, only a fair correlation between NMR and V Dmax values was observed due to the effect of the molecular size of the ring substituent. From these data, it can be concluded that the redox step (k33) is not the rate-determining step of the reaction mechanism. Thus, the monophenols are converted into diphenols, but the order of specificities towards monophenols is different to that of o-diphenols. The rate-limiting step of the monophenolase activity could be the nucleophilic attack (k51) of the oxygen atom of the hydroxyl group on the copper atoms of the active site of the enzyme. This step could also be similar to or have a lower rate of attack than the electrophilic attack (k52) of the oxygen atom of the active site of oxytyrosinase on the C-3 of the monophenolic ring. However, the rate-limiting step in the diphenolase activity of tyrosinase could be related to both the nucleophilic power of the oxygen atom belonging to the hydroxyl group at the carbon atom in the 3-position (k32) and to the size of the substituent side-chain. On the basis of the results obtained, kinetic and structural models describing the monophenolase and diphenolase reaction mechanisms for tyrosinase are proposed.

218 citations


Journal ArticleDOI
TL;DR: 4-anilinoquinoline-3-carbonitriles are effective inhibitors of EGF-R kinase with activity comparable to the 4-anILinoquinazoline-based inhibitors.
Abstract: The synthesis and SAR of a series of 4-anilino-6, 7-dialkoxyquinoline-3-carbonitrile inhibitors of epidermal growth factor receptor (EGF-R) kinase are described. Condensation of 3, 4-dialkoxyanilines with ethyl (ethoxymethylene)cyanoacetate followed by thermal cyclization gave, regiospecifically, 6,7-dialkoxy-4-oxo-1, 4-dihydroquinoline-3-carbonitriles. Chlorination (POCl(3)) followed by the reaction with substituted anilines furnished the 4-anilino-6, 7-dialkoxyquinoline-3-carbonitrile inhibitors of EGF-R kinase. An alternate synthesis of these compounds starts with a methyl 3, 4-dialkoxybenzoate. Nitration followed by reduction (Fe, NH(4)Cl, MeOH-H(2)O) gave a methyl 2-amino-4,5-dialkoxybenzoate. Amidine formation using DMF-acetal followed by cyclization using LiCH(2)CN furnished a 6,7-dialkoxy-4-oxo-1,4-dihydroquinoline-3-carbonitrile, which was transformed as before. Compounds containing acid, ester, amide, carbinol, and aldehyde groups at the 3-position of the quinoline ring were also prepared for comparison, as were several 1-anilino-6,7-dimethoxyisoquinoline-4-carbonitriles. The compounds were evaluated for their ability to inhibit the autophosphorylation of the catalytic domain of EGF-R. The SAR of these inhibitors with respect to the nature of the 6,7-alkoxy groups, the aniline substituents, and the substituent at the 3-position was studied. The compounds were further evaluated for their ability to inhibit the growth of cell lines that overexpress EGF-R or HER-2. It was found that 4-anilinoquinoline-3-carbonitriles are effective inhibitors of EGF-R kinase with activity comparable to the 4-anilinoquinazoline-based inhibitors. A new homology model of EGF-R kinase was constructed based on the X-ray structures of Hck and FGF receptor-1 kinase. The model suggests that with the quinazoline-based inhibitors, the N3 atom is hydrogen-bonded to a water molecule which, in turn, interacts with Thr 830. It is proposed that the quinoline-3-carbonitriles bind in a similar manner where the water molecule is displaced by the cyano group which interacts with the same Thr residue.

193 citations



Journal ArticleDOI
TL;DR: In this paper, the effect of chiral modifiers derived from natural cinchona alkaloids on the enantioselectivity and rate of the Pt/Al2O3-catalyzed hydrogenation of ethyl pyruvate was investigated.
Abstract: The effect of the structure of chiral modifiers derived from natural cinchona alkaloids on the enantioselectivity and rate of the Pt/Al2O3-catalyzed hydrogenation of ethyl pyruvate was investigated. The influence of the following structural elements was studied: the cinchonidine versus the cinchonine backbone; effect of the nature and the size of substituents attached to C9; effect of partial hydrogenation of the quinoline ring; effects of changes of the substituent at the quinuclidine moiety. The strongest effects on ee and somewhat less on rate were observed for changes in the O−C9−C8−N part of the cinchona alkaloid and for partial or total hydrogenation of the quinoline rings. The nature of the substituents in the quinuclidine part had a comparably minor influence. The solvent was found to have a significant effect on enantioselectivity and rate. In acetic acid, the best results were obtained with O-methyl-10,11-diydrocinchonidine (ee's up to 93%), whereas dihydrocinchonidine was the most effective mo...

186 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the regioselectivity of benzoxazine polymerization in aromatic amine-based polybenzoxazines through systematic manipulation of the monomer chemistry.
Abstract: The regioselectivity of the benzoxazine polymerization in aromatic amine-based polybenzoxazines is investigated through systematic manipulation of the monomer chemistry. The network structures of the cured materials are elucidated by FTIR and GC/MS. Selectively protecting or activating sites on the pendant aromatic ring toward electrophilic aromatic substitution with alkyl groups allows a series of materials to be developed which contain a varying amount of phenolic Mannich bridges, arylamine Mannich bridges, and methylene linkages. Activation of sites on the pendant rings by methyl substituent groups lowers the peak exotherm temperature by up to 45 °C. Temperature-modulated differential scanning calorimetry shows that in some of these materials the development of the glass transition temperature exceeds that of the curing temperature.

159 citations


Patent
30 Jun 2000
TL;DR: In this paper, the problem of providing a highly stable element showing required green El light emission by including an anode, a cathode and a porphyrin compound in an organic light emitting layer was solved.
Abstract: PROBLEM TO BE SOLVED: To provide a highly stable element showing required green El light emission by including an anode, a cathode and a porphyrin compounds in an organic light emitting layer. SOLUTION: A light emitting layer in an organic electroluminescent element includes an anode, a cathode, and a compound shown by the formula. In the formula, X represents S or 0, R1, R2 independently represent an 1-20C alkyl group, an aryl group, or a carbocyclic group, R3, R4 independently represent a 1-10C alkyl group or a branched/unbranched five/six-membered ring substituent bonded to R1, R2, and R5, R6 independently represent a branched/unbranched 1-20C alkyl group. A hole injection layer for an organic EL element is formed in the layer including a porphyrin compound, for example. As useful porphyrin compounds, non-metalcontaining phthalocyanine and metal-containing phthalocyanine are available.

156 citations


Journal ArticleDOI
TL;DR: The enantioselective outcome of transfer hydrogenation reactions that are catalysed by ruthenium(II) amino alcohol complexes was studied by means of a systematically varied series of ligands and it was found that both the substituent at the 1-position in the 2-amino-1-alcohol ligand and the substitution at the amine functionality influence the enantiOSElectivity of the reaction to a large extent.
Abstract: The enantioselective outcome of transfer hydrogenation reactions that are catalysed by ruthenium(II) amino alcohol complexes was studied by means of a systematically varied series of ligands. It was found that both the substituent at the 1-position in the 2-amino-1-alcohol ligand and the substituent at the amine functionality influence the enantioselectivity of the reaction to a large extent: enantioselectivities (ee values) of up to 95 % were obtained for the reduction of acetophenone. The catalytic cycle of ruthenium(II) amino alcohol catalysed transfer hydrogenation was examined at the density functional theory level. The formation of a hydrogen bond between the carbonyl functionality of the substrate and the amine proton of the ligand, as well as the formation of an intramolecular H⋅⋅⋅H bond and a planar H-Ru-NH moiety are crucially important for the reaction mechanism. The enantioselective outcome of the reaction can be illustrated with the aid of molecular modelling by the visualisation of the steric interactions between the ketone and the ligand backbone in the ruthenium(II) catalysts.

Journal ArticleDOI
TL;DR: The use of the m-terphenyl substituent has facilitated the synthesis of numerous unusual molecules containing main group elements as discussed by the authors, as well as highlighting potential synthetically useful derivatives.

Journal ArticleDOI
TL;DR: A series of phosphinoalkyl-substituted cyclopentadienyl chromium complexes, e.g., (η1:η5-R2PC2H4C5H4)CrCl2, have been synthesized.

Journal ArticleDOI
TL;DR: In this article, a transition metal-catalyzed heteroannulation reaction was used to synthesize 3-propylisocoumarin and artemidin.

Patent
22 May 2000
TL;DR: In this article, a novel metathesis catalysts with an imidazolidine-based ligand and methods for making and using the same are described. But the present method is limited to the use of a single atom.
Abstract: The present invention relates to novel metathesis catalysts with an imidazolidine-based ligand and to methods for making and using the same. The inventive catalysts are of formula (I) wherein : M is ruthemium or osmium; X and X1 are each independently an anionic ligand; L is a neutral electron donor ligand; and, R, R?1, R6, R7, R8 and R9? are each independently hydrogen or a substituent selected from the group consisting of C?1?-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthiol, aryl thiol, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl, the substituent optionally substituted with one or more moieties selected from the group consisting of C1-C10 alkyl, C1-C10 alkoxy, aryl, and a functional group selected from the group consisting of hydroxyl, thiol thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen. The inclusion of an imidazolidine ligand to the previously described ruthenium or osmium catalysts has been found to dramatically improve the properties of theses complexes. The inventive catalysts maintains the functional group tolerance of previously described ruthenium complexes while having enhanced metathesis activity that compares favorably to prior art tungsten and molybdenum systems.

Journal ArticleDOI
TL;DR: In this paper, two strategies for the construction of extended arrays of transition metal-containing molecules linked via hydrogen bonds are described, the first approach connects the transition metal to the ligand bearing the hydrogen-bonding group(s) via a coordinative bond.
Abstract: Two strategies are described for the construction of extended arrays of transition metal-containing molecules linked via hydrogen bonds. The first approach connects the transition metal to the ligand bearing the hydrogen-bonding group(s) via a coordinative bond. Thus, coordination complexes with peripheral hydrogen-bonding functional groups constitute the (molecular) building blocks of the assembly. The ligands, substituted pyridines, have been selected to provide rigidity and thus permit the metal coordination geometry to guide the direction of propagation of the hydrogen-bonded links between building blocks. The second approach uses arenes bearing hydrogen-bonding functional groups, the arenes being π-bound to transition metals as is typical of sandwich and half-sandwich organometallic compounds. In the first approach the metal can be viewed as serving a directing role in propagation of the hydrogen bonded assembly. In the second, the metal can be thought of as a (potentially functional) appendage to an organic hydrogen-bonded array, where substituent position at the arene ring serves the directing role for propagation. Examples presented for discussion of the coordination chemistry approach are compounds of the form [PtL4]X2 (L = nicotinamide or isonicotinamide; X− = Cl− or PF6−). Examples presented in the context of the organometallic approach are members of the series [Cr{η6-C6H6 − n(CO2H)n}(CO)3], where n = 1–3.

Patent
10 Nov 2000
TL;DR: In this paper, a method for preparing a functionalized polymer comprising the steps of preparing a pseudo-living polymer by polymerizing conjugated diene monomer with a lanthanide-based catalyst is presented.
Abstract: A method for preparing a functionalized polymer comprising the steps of preparing a pseudo-living polymer by polymerizing conjugated diene monomer with a lanthanide-based catalyst, and reacting the pseudo-living polymer with at least one functionalizing agent defined by formula (I) where A is a substituent that will undergo an addition reaction with a pseudo-living polymer, R1 is a divalent organic group, R2 is a monovalent organic group, and each R4, which may be the same or different, is a monovalent organic group or a substituent defined by -OR5 where R5 is a monovalent organic group, with the proviso that A, R?1, R2, R4, and R5? are substituents that will not protonate a pseudo-living polymer. Also, the functionalized polymer and a vulcanizable composition containing the polymer.

Journal ArticleDOI
TL;DR: The p-styrenyl substituent borne by the organoimido-ligand in the Lindqvist derivative as discussed by the authors allows the polyoxometalate complex to be introduced as a pendant group in polystyrene compositions via conventional free radical-induced copolymerization.

Journal ArticleDOI
TL;DR: The second-order rate constants for deprotonation of neutral α-carbonyl carbon acids and cationic esters are attributed to the presence of the positively charged ammonium substituent at the latter carbon acids as discussed by the authors.
Abstract: Second-order rate constants for carbon deprotonation of glycine zwitterion, N-protonated glycine methyl ester, betaine methyl ester, and betaine by deuterioxide ion in D2O have been determined by following deuterium exchange into these carbon acids in buffered solutions at 25 °C and I = 1.0 (KCl) by 1H NMR spectroscopy. The data were used to calculate the following carbon acidities for glycine zwitterion and its derivatives in aqueous solution: +H3NCH2CO2-, pKa = 28.9 ± 0.5; +H3NCH2CO2Me, pKa = 21.0 ± 1.0; +Me3NCH2CO2Me, pKa = 18.0 ± 1.0; +Me3NCH2CO2-, pKa = 27.3 ± 1.2. The rate constants for deprotonation of glycine methyl ester by Bronsted base catalysts are correlated by β = 0.92. Two important differences between structure−reactivity relationships for deprotonation of neutral α-carbonyl carbon acids and cationic esters are attributed to the presence of the positively charged ammonium substituent at the latter carbon acids: (1) The smaller negative deviation of log kDO from the Bronsted correlation f...

Patent
03 Aug 2000
TL;DR: An electrolyte composition comprising a compound represented by the following general formula (1): wherein R represents a substituent containing a −(CR 1 R 2 −CR 3 R 4 −O) n-bond (in which R 1 to R 4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20), Q represents an atomic group forming an aromatic cation having a 5- or 6-membered ring structure with a nitrogen atom, which may have a substitutionuent; X − represents an anion as discussed by the authors.
Abstract: An electrolyte composition comprising a compound represented by the following general formula (1): wherein R represents a substituent containing a —(CR 1 R 2 —CR 3 R 4 —O) n — bond (in which R 1 to R 4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20); Q represents an atomic group forming an aromatic cation having a 5- or 6-membered ring structure with a nitrogen atom, which may have a substituent; and X − represents an anion. A photoelectric conversion device comprising the electrolyte composition and a photo-electrochemical cell composed thereof are also provided.

Journal ArticleDOI
TL;DR: In this paper, electron-donating substituents increase the C-N bond length R(C-N),, Einv,a nd the pKa,w hereas electron-withdrawing substituent have the opposite effect.
Abstract: The aniline molecule is nonplanar, with its NH2 group lying at an angle of approximately 42 to the plane of the benzene ring. Substituents on the phenyl ring alter this out-of-plane angle as well as other molecular properties such as the ring bond lengths and angles, the barrier to inversion Einv ,a nd the pKa of the amino group. Ab initio 6-311G quantum chemical calculations have been employed to examine these substituent influences and the extent to which they are interrelated. Electron-donating substituents increase the C—N bond length R(C—N),, Einv ,a nd the pKa ,w hereas electron-withdrawing substituents have the opposite effect. Among the molecular parameters that might serve as regression indicators for these changes, Hammett constants, which traditionally have been used to represent substituent electronic effects, yield fair to good correlations for R(C—N) (r 2 D 0.797), (r 2 D 0.804), Einv (r 2 D 0.829), and the amino group pKa (r 2 D 0.931) for aniline and 18 substituted anilines. Of several measures of atomic charge, the Mulliken and electrostatic charges on the amino nitrogen atom show essentially no correlation with these properties. In contrast, the natural charge Qn on the amino nitrogen is well correlated with the bond length R(C—N) (r 2 D 0.889), (r 2 D 0.932), Einv (r 2 D 0.839), and the amino group pKa (r 2 D 0.960). This latter result suggests that the natural charge, rather than either the Mulliken or electrostatic charges, may be the preferred charge descriptor for correlation purposes. Inclusion of electron correlation at the MP2 level increases the correlations of Einv with both (r 2 D 0.951) and Qn (r 2 D 0.892). c 2000 John Wiley & Sons, Inc. Int J Quantum Chem 80: 1107-1115, 2000

Journal ArticleDOI
TL;DR: In this article, the effect of electron-donating substituents at the 4 position has been explored for its effect on photolysis efficiency, and the 4-dimethylamino analogue was essentially inert, while a 5-alkyl substituent, that blocks unwanted nitration at this position, reduced the beneficial effect of the 4methoxy group.

Journal ArticleDOI
TL;DR: In this paper, rate studies of benzene and related alkoxy-substituted aromatics by n-BuLi/TMEDA mixtures implicate similar mechanisms in which the proton transfers are rate limiting with transition structures of stoichiometry.
Abstract: Rate studies of the lithiation of benzene and related alkoxy-substituted aromatics by n-BuLi/TMEDA mixtures implicate similar mechanisms in which the proton transfers are rate limiting with transition structures of stoichiometry [(n-BuLi)2(TMEDA)2(Ar−H)]⧧ (Ar−H = benzene, C6H5OCH3, m-C6H4(OCH3)2, C6H5OCH2OCH3, and C6H5OCH2CH2N(CH3)2). Cooperative substituent effects and an apparent importance of inductive effects suggest a mechanism in which alkoxy−lithium interactions are minor or nonexistent in the rate-limiting transition structures. Supported by ab initio calculations, transition structures based upon triple ions of general structure [(n-Bu)2Li]-//+Li(TMEDA)2 are discussed.

Journal ArticleDOI
TL;DR: In this paper, a novel bithiophene with a pendant fullerene and its electrochemical polymerisation was reported, and electron transfer from the donor cable (polythiophene) to the pendant acceptor cable (fullerene moieties).

Journal ArticleDOI
TL;DR: In the chemistry of main-group elements the pentamethylcyclopentadienyl (Cp*) group represents a very important substituent as discussed by the authors, and the steric requirements of the σ- or π-bound Cp* group enable the kinetic stabilization of otherwise highly reactive species.
Abstract: In the chemistry of main-group elements the pentamethylcyclopentadienyl (Cp*) group represents a very important substituent. Owing to its quite variable bonding modes, ranging from mainly ionic to mainly covalent and from η5via η2/3 to η1, an effective adjustment to the electronic situation at the respective element centre is feasible. Furthermore, the steric requirements of the σ- or π-bound Cp* group enable the kinetic stabilization of otherwise highly reactive species. Covalent Cp*–element bonds are comparatively weak, consequently allowing fast sigmatropic and haptotropic rearrangement processes. A further consequence is that the Cp* radical as well as the Cp*− anion are potential leaving groups. This phenomenon forms the basis of a rich faceted substitution and elimination chemistry. As proof of this statement, several examples from phosphorus, silicon, and gallium chemistry are presented.

Journal ArticleDOI
TL;DR: The overall reaction is a nucleophilic substitution and proceeds via initial reaction of the organic nucleophile with a meso carbon yielding an anionic species which is hydrolyzed to a porphodimethene, formally constituting an addition reaction to two Cm positions.
Abstract: Porphyrins react readily with organolithium reagents, preferentially in the meso positions. The overall reaction is a nucleophilic substitution and proceeds via initial reaction of the organic nucleophile with a meso carbon yielding an anionic species which is hydrolyzed to a porphodimethene (5,15-dihydroporphyrin), formally constituting an addition reaction to two Cm positions. Subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yields meso-substituted porphyrins. The reaction is highly versatile as it is accomplished in high, often quantitative yields with various alkyl or aryl lithium reagents. In addition, LiR can be used for reaction with a variety of metal complexes (best with NiII, but also with ZnII, CuII, and CoII) and most useful with free base porphyrins. Similarly beneficial this reaction can be used in sequence for the introduction of 1, 2, 3, or 4 (different) meso substituents giving for the first time an entry into any desired meso-substituted porphyrin. If meso-substituted porphyrins are used, reaction with LiR can be used for either the preparation of phlorins (already known reaction), porphodimethenes (5,15-dihydroporphyrins, including those with exocyclic double bonds, for example, 51,52-didehydroporphyrins) or chlorins (2,3-dihydroporphyrins) depending on the substituent type in the reactant porphyrins. Thus, this reaction presents a generally applicable method for the facile and versatile functionalization of porphyrins.

Journal ArticleDOI
TL;DR: The influence of base and solvent in Suzuki cross-coupling reaction on various 2-substituted-3-iodoimidazo[1,2-a]pyridines was reported and optimized yields were obtained using strong bases in DME.
Abstract: The influence of base and solvent in Suzuki cross-coupling reaction on various 2-substituted-3-iodoimidazo[1,2-a]pyridines was reported. The reactivity was largely influenced by nature of the substituent. Optimized yields and shortened times of reaction were obtained using strong bases in DME.

Patent
30 Aug 2000
TL;DR: A class of substituted and/or ring-fused pyrazolo[3,4-b]pyridine derivatives, possessing an optionally substituted cycloalkyl, phenyl or heteroaryl substituent on the pyrazole nitrogen atom adjacent the pyridine nucleus, are selective ligands for GABAA receptors, in particular having high affinity for the β2 and β3 subunit thereof, and are accordingly of benefit in the treatment and prevention of adverse neurological disorders, including anxiety and convulsions as mentioned in this paper.
Abstract: A class of substituted and/or ring-fused pyrazolo[3,4-b]pyridine derivatives, possessing an optionally substituted cycloalkyl, phenyl or heteroaryl substituent on the pyrazole nitrogen atom adjacent the pyridine nucleus, and an optionally substituted cycloalkyl-alkoxy, aryl-alkoxy or heteroaryl-alkoxy substituent on the carbon atom adjacent the pyridine ring nitrogen atom, are selective ligands for GABAA receptors, in particular having high affinity for the β2 and/or β3 subunit thereof, and are accordingly of benefit in the treatment and/or prevention of adverse neurological disorders, including anxiety and convulsions.

Journal ArticleDOI
TL;DR: The proposed semi-quantitative model, which explains most hydrogen-bonded motifs as a combination of the effects of substituents at C3 and C5, has been examined as a function of the steric and polarizability effects of these substituent effects represented by molar refractivity.
Abstract: The secondary structure of 1H-unsubstituted pyrazole derivatives bearing only one hydrogen donor group and one or more acceptor groups has been analyzed in terms of some descriptors representing the substituents at C3 and C5. The substituent at C4 appears to affect mainly the tertiary or quaternary structure of these compounds. The proposed semi-quantitative model, which explains most hydrogen-bonded motifs as a combination of the effects of substituents at C3 and C5, has also been examined as a function of the steric and polarizability effects of these substituents represented by molar refractivity. The model also applies to other five-membered rings (1,2,4-triazoles, 1,2,4-diazaphospholes and 1,2,4-diazaarsoles). Furthermore, ab initio calculations at RHF/6-31G* have been performed to discover the relative stability of three of the four hydrogen-bond patterns displayed by several symmetrical pyrazoles (dimers, trimers, tetramers). The fourth motif, catemers, has only been discussed geometrically.

Patent
16 Aug 2000
TL;DR: In this article, a process for preparing a novel complex compound having a band gap corresponding to a blue colour and a high melting point and an organic electroluminescent device are provided which improve thermal stability when applied to electrolUMinescent devices.
Abstract: PURPOSE: A process for preparing a novel complex compound having a band gap corresponding to a blue colour and a high melting point and an organic electroluminescent device are provided which improve thermal stability when applied to electroluminescent devices. CONSTITUTION: An organic metal complex represented by the general formula 1, an organic electric field electroluminescent device comprising a layer containing the complex between the positive and negative poles and processes for preparing thereof are described. In formula, R1,R2,R3 are each independently or simultaneously substituents selected from the group consisting of H, lower hydrocarbon, halogen, alkoxy, arylamine, nitro, nitryl, aldehyde, ester, sulfurous hydrocarbon(-SR), aromatic hydrocarbon, and C1-12 hetero ring compounds; ring A is a ring compound selected from the group consisting of an aromatic comprising a nitrogen atom of an imidazole group and an adjacent carbon atom, an aromatic containing C5-12 hetero ring and C4-11 hetero ring containing N-R4 (R4 is a substituent selected from the group consisting of H, lower hydrocarbon, saturated aliphatic hydrocarbon, and aromatic ring compound; the ring B is a ring compound selected from an aromatic which combines with a carbon atom of an imidazole group or a C5-12 hetero ring; M is a metal selected from the group consisting of beryllium, zinc, magnesium, aluminium, gallium, and indium; n is an integer from 2 to 3.