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    1.Spirally Configured cis-Stilbene/Fluorene Hybrids as Ambiplor Templates for Organic Light Emitting Diode Applications

    Organic light emitting diodes (OLEDs) have been intensively investigated in the recent years for their potential applications in next generation full-color at panel displays and solid state lighting. However, the recombination efficiency of holes and electrons with unbalanced-charge carriers is one of the key factors for making bad device efficiencies. Therefore, we developed a new class of cis-stilbene/fluorene spiro hybrid systems with hole-transporting, electron-transporting and ambipolar organic fluorescent materials for optoelectronic applications. These types of materials exhibited a stable amorphous glassy state (Tg:120-167 oC) and stable decomposition temperatures (Td: >400 oC). One of the fluorescent materials, N-STIF-P(O)Ph2, had ambipolar charge transport feature with balanced hole and electron mobilities (μh: 6.510-6 cm2/Vs
    [0/1]
    13: M = Co). When the slightly more steric hindered amidinate ligand (Li[HC(NDep)2]) was employed to react with anhydrous FeCl2 and CoCl2, the lantern type complexes, Fe2[(μ-κ2-HC(NDep)2]3 (11) and Co2[(μ-κ2-HC(NDep)2]3 (15) are also the major products. [0/1]
    4,5-b_]–dithiophene (m-FP-BTDT), were grown on the Au (111) and modified Au (111) substrate as the organic semiconductor thin films, respectively. The growth mechanisms, the molecular orientations and the electronic structure of the thin films were analyzed via XPS, NEXAFS and UPS. In addition, the above results were combined with the XRD and AFM data to reach a thorough understanding of the performances of various OFETs. The thermal desorption data show that the chemisorbed P-BTDT layer remains thermally stable up to 750 K on Au(111). However, P-BTDT desorption on Au-BT substrate is found to derive exclusively from physisorption state, and chemisorption desorption is entirely suppressed. Based on the change of XPS intensity with the amount of P-BTDT deposited, it is concluded that the growth of P-BTDT film on Au(111) follows the Stranski-Krastanov mechansim, i.e., a completion of one monolayer (2D growth) followed by a 3D crystallite growth. In comparison, for the growth of P-BTDT on Au(111)-benzenethiolate, a pseudo 2D-like growth is observed. From the results of UPS, the change of work function and valence band spectrum with the film-thickness is in accord with this growth behavior. The results obtained by XPS are also in agreement with UPS observations. The molecules of the multilayer grown on Au(111)-BT have their aromatic rings inclined toward the surface by an average 66°, as determined by NEXAFS data. For the thick film grown on Au(111), out-of-plane x-ray diffraction reveals the presence of several crystallite alignment schemes. In contrast, the XRD data of the thicker layer grown on Au(111)-BT show (002) diffraction peaks only, indicating that the crystal orientation of the thin film is (002) preferred. Therefore, we can change the crystal structure and control the growth behavior of the thin film through different modification of substrates, leading to an improved performance of the OFETs. The results show that P-BTDT thin film that is grown on BT-Au can yield a better OFET mobility up to 3.0 × 10-2 cm2/Vs with thickness of 120 nm.
    In order to shift energy level of LUMO toward lower value, we also prepared m-FP-BTDT organic semiconducting thin films and investigated their properties. XPS intensity analysis shows that on Au(111), m-FP-BTDT film grows according to Stranski–Krastanov (SK) mode. It is interesting to note an abrupt increase of Au 4f signal at around one ML of m-FP-BTDT, which is explained by the production of excess Au adatoms, accompanied by the lifting of the herringbone reconstruction of Au(111). In comparison, the initial growth of m-FP-BTDT on Au-BT proceeds via a pseudo layer-by-layer growth mechanism. NEXAFS data show that m-FP-BTDT molecules on Au-BT adopt a more erected configuration, the angle between the molecule and substrate is 62.5°, resulting in a better cofacial π-stacking. The XRD pattern reveals that the crystal growth orientation of m-FP-BTD thin film is along c axis. Work function for the thick m-FP-BTDT film on Au-BT is determined with UPS as 4.62 eV and the hole injection barrier as 0.94 eV. According to above results the thin film of m-FP-BTDT grown on Au(111)-BT is expected to produce better carrier transport phenomenon.
    [0/1]
    4,5-b’] dithiophene (P-BTDT) and its derivative, monofluorine-substituted 2–phenylbenzo [d,d_]thieno [3,2-b [0/1]
    A. M. Mebel [2/2]
    A series of chiral oxidovanadium (V) methoxides were derived from 3,5-disubstituted-N-salicylidene α-amino carboxylic acids and tetrazoles. These complexes serve as enantioselective catalysts for asymmetric reduction and aldol reaction.
    We are the first group that used chiral vanadyl (V) complexes to study the asymmetric reduction. In this study, α-keto amides served as the best substrate class and methanol-modified pinacolborane served as the best reducing agent among five different reducing agents examined. With catalysts 1a (C3 = tBu, C5 = Br) and 1a’ (C3 = tBu, C5 = Br), up to 62% yield and 85% ee (R form) of the α-hydroxyamides were afforded at -20 oC in toluene.
    In the past five years, we have already found that chiral vanadyl (V) complexes derived from N-salicylidene α-amino carboxylic acids 1a and tetrazoles 11a (C3 = 2,5-dimethoxyphenyl, C5 = NO2) could achieve complementary asymmetric catalytic aldol processes in addition of silyl ketene acetals (SKA) to isatins at -40 oC in dichloromethane. Herein we further optimized these reactions in the case of 5-nitro-isatin by adding trichloroethanol to facilitate turnover, leading to the corresponding aldol product in moderate yield (61%) and good enantioselectivity (88% ee, S form) with catalyst 1a. Without any additives, using catalyst 11a could furnish a series of R form isatin adducts with up to 97% yield and 90% ee in a complementary manner. Molecular simulations of the adducts between these two catalysts and N-benzylisatin indicated that the preferred coordination mode involve in a facile π-π interaction between the N-benzyl moiety and N-salicylidene template of catalyst 1a to avoid concomitantly the steric hindrance of the C3 tert-butyl. On the other hand, another π-π interaction between the C3 2,5-dimethoxylphenyl group of catalyst 11a and the N-benzyl group of the isatin to avoid concomitantly the el-el repulsion with the tetrazole moiety is involved, leading to a complementary, enantiofacial exposure of the carbonyl moiety in the N-benzylisatin.
    [0/1]
    Aaltonen T [1/1]
    Abd-Elazem IS [1/1]
    Abstract
    Alzheimer's disease ( AD ) is one of the most fatal neurodegenerative disease .The
    major pathogenesis of Alzheimer's disease ( AD ) is neurofibrillary tangles and enile plaques , and the aggregation of the A 40 plays a crucial role in the pathogenesis of the senile plaques of Alzheimer's disease (AD) . Although the amyloid -protein has been studied extensively , the mechanisms of A aggregation in brain remain unclear . In this study , we investigate the influence of the collagen related peptides on A aggregation.
    Here we chose the most important region of amyloid -protein responsible for aggregation , residues 16-22 (KLVFFAE) , as our study model . We incorporated the collagen sequence (POG)n into Aβ(16-22) and synthesized eight peptides:
    WT-A(16-22) , A(16-22)-(POG)6 , A(16-22)-(POG)7, A(16-22)-(POG)10 , (POG)7-A(16-22) and (POG)10-A(16-22).Two collagen peptides (POG)7 and (POG)10 were synthesized as the control peptides for comparison.We used fluorescence spectroscopy, TEM , CD , FT-IR and DLS to study whether the collagen sequence can inhibit A aggregation .
    CD measurements indicate that the Aβ(16-22) sequence at the N-terminus of (POG)n does not stabilize the triple-helical structure of collagen and such peptides have a weaker thermal stability than (POG)n .In contrast,when the Aβ(16-22) sequence is attached to the C-terminus of (POG)n, it can stablize the triple-helical structure of collagen.
    From aggregation studies, we found that the amyloid aggregation did not occur when (POG)7 was incorporated into A(16-22) but the aggregation was enhanced when (POG)10 incorporated into A(16-22).The mixing experiments indicate that (POG)7A cannot inhibit the aggregation of WT-A(16-22) while A(POG)6 and A(POG)7 can.The inhibition effect may not be due to the triple-helical structure of collagen but the PPⅡ structure.
    [0/1]
    ABSTRACT
    This dissertation describes development of new synthetic organic transformations by using gold and copper salts. The use of these soft alkynophilic metals enables mild, diastereoselective and efficient transformations of a variety of readily available substrates to wide range of synthetically useful and biologically important N, O containing heterocyclic and carbocyclic products. For better understanding the thesis is divided into four chapters.

    The first chapter deals with the Gold-catalyzed oxidative cyclizations of cis-3-En-1-ynes to form cyclopentenone derivatives. The title reaction for synthesizing cyclopentenone derivatives utilizes a gold complex and 8-methylquinoline oxide as the catalyst system. The value of such reactions is reflected by their applicability to a broad range of benzene- and nonbenzene-derived substrates, thus giving various indanone and cyclopentenone derivatives, respectively. Such products are not attainable using diazocarbonyl reagents, as the gold carbenoids tend to react with C-H bonds.

    The second chapter deals with the gold-catalyzed oxidative cyclizations of 1,4-enynes were used to study the γ-effect on the Wagner–Meerwein rearrangement. Both experimental and theoretical work disclose that a gold substituent in the γ-position can direct a stereospecific 1,2 shift of the anti-β-substituent regardless of its intrinsic properties.

    The third chapter describes gold-catalyzed reactions of 3,5- and 3,6-dienynes with 8-alkyl- quinoline oxides results in an oxidative cycloaddition with high stereospecificity, this process involves a catalytic activation of a quinoline framework. The reaction mechanism involves the intermediacy of α-carbonyl pyridinium ylides (I) in a concerted [3+2]-cycloaddition with a tethered alkene.

    The fourth chapter presents the work aim at one-step construction of complex and important molecular frameworks via Cu-catalyzed oxidations of cheap tertiary amines. Cu-catalyzed aerobic oxidations of N-hydroxyaminopropenes to form C2-symmetric N- and O-functionalized cyclohexanes.
    [0/1]
    Abstract
    This dissertation describes development of new synthetic organic transformations by using gold salts. The use of this soft alkynophilic metal enables mild, diastereoselective and efficient transformations of a variety of readily available substrates to wide range of synthetically useful highly functionalized products. For better understanding the thesis is divided into four chapters.
    The first chapter deals with the gold-catalyzed 1,2-oxoarylations of nitriles with pyridine-derived oxides. This is the first success in the gold-catalyzed oxoarylations of nitriles using gold carbenes as initiators leading to benzo[d]azepine frameworks. Such azacyclic core is one of the most commonly encountering skeletons in nature and the core scaffold has a wide spread application in structural, biological importance. These oxoarylations were also achieved satisfactorily in intermolecular three-component oxidations, including diverse alkenyldiazo esters, nitriles, and pyridine-based oxides.



    The second chapter deals with the gold-catalyzed regiocontrolled [2+2+2]-cycloadditions of ynamides with two discrete nitriles to construct 4-aminopyrimidine cores pharmaceutically important structural motifs. The utility of this new cycloaddition is manifested by the excellent regioselectivity with applicable ynamides and nitriles over a wide scope.



    The third chapter describes the retention of stereochemistry in gold-catalyzed formal [4+3]-cycloaddition of epoxides with arenyanamides. The utility of this new [4+3]-Cycloaddition reaction is manifested by a wide scope of arenynamides and epoxides. An SN2-type front-side attack of phenyl at the oxiranyl ring is expected to cause the retention of stereochemistry.



    The fourth chapter presents gold-catalyzed 1,2-difunctionalizations of aminoalkynes using Only N- and O-containing oxidants. In the presence of IPrAuNTf2, nitrosobenzenes implements a novel oxoimination of aminoalkynes to form 2-oxoiminylamides that are then subjected to NaBH4 reduction in situ to deliver 2-aminoalcohols.
    [0/1]
    Abstract
    This dissertation describes development of new synthetic organic transformations by using transition metal catalysis. The use of gold and rhodium metals enables mild, diastereoselective and efficient transformations of variety of readily available substrates to wide range of synthetically useful nitrogen and oxygen containing heterocyclic products. For convenience and better understanding, this thesis is divided into four chapters.
    The first chapter describes the two new formal cycloaddition reactions between nitrosobenzenes and alkenylgold carbenoids. We obtained quinoline oxides in good to better yields from the gold-catalyzed [3+3]-cycloadditions between nitrosobenzenes and alkenyldiazo esters. For propargyl esters, its resulting gold carbenes react with nitrosobenzene to give alkenylimine, followed by a [4+2]-cycloaddition with nitrosobenzene to form 1, 2-oxazines.

    The second chapter deals with the development of an oxa-Povarov reaction/carbene generation sequence for alkenyldiazocarbonyl compounds. A triflic acid catalyzed reaction of vinyl diazoacetate with diphenoxymethylbenzene to give diazo-containing cycloadducts stereoselectively with fruitful range of substrate scope. The dihydrobenzopyran core moiety found in many natural product and bioactive molecules.

    The third chapter explains, the gold-catalyzed reactions between vinyldiazo carbonyl species and acetals to obtain selectively E-configured alkyl 3,5-dimethoxy-5-pent-2- enoates in good yields. According to our experimental data, this reaction sequence involves an initial Prins-type reaction, followed by gold-carbene generation. The success of this Prins-type reaction indicates a stabilization effect of the diazo functionality on the adjacent carbocation.

    The fourth chapter provides gold-catalyzed oxa-Povarov reactions involving readily available diaryloxymethylarenes and aryl-substituted alkenes to give dihydrobenzopyrans
    [0/1]
    Abstract
    Treatment of the diamindopyridyl ligand,
    4-Me-2,6-(HN-2,6-iPr2C6H3)2C5H3N, with WCl4(DME) (DME =
    dimethoxyethane) in the presence of 2 equiv of DBU
    (DBU=1,8-Diazabicyclo[5.4.0]undec-7-ene) gave the ditungsten complex,
    W2Cl4(μ-κ2-4-Me-2-(HN-2,6-iPr2C6H3)2-6-(N-2,6-iPr2C6H3)C5H2N)2 (1).
    NMR spectroscopy and X-ray studies showed that 1 have two amino
    arms and chloro groups point towards the protons of those two amino
    groups. We then reduced the bulk of the diamindopyridyl ligand by
    substituting Dep (2,6-Et2C6H3) for Dipp (2,6-iPr2C6H3), and the product
    W2Cl4(μ-κ2-4-Me-2-(HN-2,6-Et2C6H3)-6-(N-2,6-Et2C6H3)C5H2N)2 (2)
    structurally similar to 1 was isolated upon reacting with WCl4(DME).
    Subsequently, attempts to reduce 1 and 2 by KC8 were carried out.
    However, the reduced product of 1 decomposes rapidly in solutions,
    while the free ligand was the major product upon reduction of 2.
    In the second part of this thesis, we employed
    amidophosphinopyridiyl ligand 2-(HN-2,6-iPr2C6H3)-6-P(C6H5)2pyridine
    to stabilize metals. Treatment of CoCl2 or MnCl2 with
    (Et2O)Li[κ1-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N] yielded the
    mononuclear compounds
    (OEt2)Co[κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N]2 (5) and
    (THF)Mn[κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N]2 (6), respectively.
    Both metal centers adopt a square pyramidal configuration. The reaction
    between (Et2O)Li[κ1-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N] and CuI
    yielded the trinuclear complex
    IV
    (CuI)Cu2[μ3-κ1:κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N]2 (7), where CuI
    is ligated by two phosphine groups. The structure of 7 is similar to the
    previously prepared tricopper complex
    Li{Cu3[μ-κ3-4-methyl-2,6-bis(N-2,6-iPr2C6H3)2pyridine]2}, in which three
    copper atoms are arranged in a linear conformation. Reduction of 7 gave
    the dicopper compound Cu2(μ-κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N)2
    (8) (vide infra), where each Cu is linear and ligated by two N atoms.
    Alternatively, compound 8 was isolated from the reaction of
    (Et2O)Li[κ1-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N] and CuI. Interestingly,
    treatment of 7 with Pd(PEt3)3, Ni(PEt3)4 and Fe2(CO)9 led to the
    formation of three heterotrinuclear complexes
    (PEt3)PdCu2[μ3-κ1:κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N]2 (9),
    (PEt3)NiCu2[μ3-κ1:κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N]2 (10) and
    (CO)3FeCu2[μ3-κ1:κ2-2-(N-2,6-iPr2C6H3)-6-P(C6H5)2C5H3N]2 (13),
    respectively. The conformation of these three heterotrinuclear complexes
    is roughly the same, in which Pd, Ni and Fe atoms replace the
    phosphine-bound CuI fragment. Notably, three metals in 13 are arranged
    in a linear mode. Although the iron center in 13 adopts a trigonal
    bipyrimidal conformation and three CO ligands are in equatorial positions,
    the angles between the three carbonyl groups are not equivalent
    [0/1]
    ABSTRACT
    A series of pyrrole structure-based CB1 receptor ligands was constructed by the Paal-Knorr reaction. Pyrrole amides 72 and 96, which were substituted with (R)-1-hydroxy-3-methyl-1,1-diphenylbutan-2-yl, exhibited high affinity and excellent selectivity for CB1 receptor (IC50 = 4.2 nM and 1.9 nM, respectively). The presence of cyclohexyl group on pyrrole amides 64 (IC50 = 15.2 nM) and 94 (IC50 = 14.3 nM) also showed promising binding affinity enhancement to CB1 receptor. Moreover, C3-carboxamides of pyrrole compounds substituted with terminal ethyne, which contain not only symmetric dialkyl group but also one long alkyl chain such as 75, 77, 79, and 80 demonstrated high CB1 binding affinity. These results suggested that pyrrole amides 41 and 42 might become candidates to provide physicochemical benefits towards CB1. Compound 104 (IC50 = 12.0 nM for CB1), a pyrazole derivative by replacement of rimonabant C-3 group with cyclohexylethynyl amide, shows the same affinity as rimonabant C-3 for CB1 receptor, indicating that terminal ethyne unit provides unusual enhancement of receptor-ligand interaction to inactivate CB1 receptor.

    Key Words: Rimonabant
    [0/1]
    Abu Sohel, Shariar Md. [1/1]
    Abu Sohel SM [1/1]
    Adak AK [1/1]
    Adak, Avijit Kumar [4/4]
    ADAMS RD [4/4]
    Adamson, GW [1/1]
    Airaksinen SMK [1/1]
    Albert H Wan [2/2]
    Albinati A [1/1]
    Alcalde MI [0/1]
    Alexander M. Mebel [3/3]
    Showing items 1-25 of 5013. (201 Page(s) Totally)
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