Abstract  In the present contribution, wavelength has been used as a tunable parameter to achieve selective control of the photophysics of two novel asymmetric bichromophoric dyads composed of naphthalene units, i.e., 6-methoxynaphthalene (NPX) and 1-methylnaphthalene (NAP) derivatives, with different electronic properties, connected by an amide spacer [(S,S) and (S,R)-NPX-NAP]. As model systems, relevant monochromophoric compounds (NPX-M and NAP-M) have also been investigated. While upon excitation at 325 nm the light energy remained in the NPX moiety, at 290 nm an efficient singlet-singlet energy transfer (phi(SSET) of about 97%) from the NAP unit to the NPX chromophore dominated. A remarkable stereodifferentiation was observed in the excited-state quenching by triethylamine via exciplex formation. The results demonstrate that it is possible to control configuration-dependent interactions in the excited state by wavelength tuning. This can be rationalized through intramolecular interactions of pi systems leading to modulation of the redox properties.

Abstract  Normobaric hyperoxia (NBO) and cilostazol (6-[4-(1-cyclohexy-1H-tetrazol-5-yl)butoxyl]-3,4-dihydro-2-(1H)-quinolinone) (a selective inhibitor of phosphodiesterase 3) have each been reported to exert neuroprotective effects against acute brain injury after cerebral ischemia in rodents. Here, we evaluated the potential neuroprotective effects of combination treatment with NBO and cilostazol against acute and subacute brain injuries after simulated stroke. Mice subjected to 2-h filamental middle cerebral artery (MCA) occlusion were treated with NBO (95% O(2), during the ischemia) alone, with cilostazol (3 mg/kg i.p. after the ischemia) alone, with both of these treatments (combination), or with vehicle. The histological and neurobehavioral outcomes were assessed at acute (1 day) or subacute (7 days) stages after reperfusion. We measured regional cerebral blood flow (rCBF) during and after ischemia by laser-Doppler flowmetry and recovery (versus vehicle) in the combination therapy group just after reperfusion. Mean acute and subacute lesion volumes were significantly reduced in the combination group but not in the two monotherapy groups. The combination therapy increased endothelial nitric-oxide synthase (eNOS) activity in the lesion area after ischemia versus vehicle. Combination therapy with NBO plus cilostazol protected mice subjected to focal cerebral ischemia by improvement of rCBF after reperfusion, in part in association with eNOS activity.

Abstract  A kind of amphiphilic derivatives of chitosan (2-hydroxyl-3-butoxyl)-propylcarboxymethyl-chitosan (HBP-CMCHS), has been synthesized, and the critical micelle concentration (cmc) of HBP-CMCHS was detected by the fluorescence method. The puerarin-loaded HBP-CMCHS micellar system was prepared by physical entrapped method. Result showed that when adding the same amount of puerarin, the solubilizing capacity was enhanced by increasing the concentration of HBP-CMCHS and temperature. Puerarin-loaded micellar system of HBP-CMCHS was characterized by TEM and DLS. TEM photograph revealed that the micelles were spherical and puerarin was solubilized in the cores of the spherical polymeric micelles. DLS showed that after solubilization the size of the micelles became bigger. In vitro tests showed that puerarin was slowly released from micellar solution and the release lasted up to 60 h by means of the dialysis method.

Abstract  A kinetic study of the hydrogen atom abstraction reactions from propanal (PA) and 2,2-dimethylpropanal (DMPA) by the cumyloxyl radical (CumO•) has been carried out in different solvents (benzene, PhCl, MeCN, t-BuOH, MeOH, and TFE). The corresponding reactions of the benzyloxyl radical (BnO•) have been studied in MeCN. The reaction of CumO• with 1,4-cyclohexadiene (CHD) also has been investigated in TFE solution. With CHD a 3-fold increase in rate constant (k(H)) has been observed on going from benzene, PhCl, and MeCN to TFE. This represents the first observation of a sizable kinetic solvent effect for hydrogen atom abstraction reactions from hydrocarbons by alkoxyl radicals and indicates that strong HBD solvents influence the hydrogen abstraction reactivity of CumO•. With PA and DMPA a significant decrease in k(H) has been observed on going from benzene and PhCl to MeOH and TFE, indicative of hydrogen-bond interactions between the carbonyl lone pair and the solvent in the transition state. The similar k(H) values observed for the reactions of the aldehydes in MeOH and TFE point toward differential hydrogen bond interactions of the latter solvent with the substrate and the radical in the transition state. The small reactivity ratios observed for the reactions of CumO• and BnO• with PA and DMPA (k(H)(BnO•)/k(H)(CumO•) = 1.2 and 1.6, respectively) indicate that with these substrates alkoxyl radical sterics play a minor role.

Abstract  At 220 K in cyclopropane solvent, hydrogen-atom abstraction from allyl alcohol by Bu(1)O(.), EtO(.), PhMe(2)CO(.), (Me(3)Si)(2)N-. or triplet-state acetone gives the 1-hydroxyallyl radical 3 as a ca. 3:1 mixture of the syn- and anti-isomers. In contrast, the allyloxyl radical does not react with allyl alcohol to bring about abstraction of hydrogen, but instead undergoes a more rapid alcohol-promoted rearrangement to give 3 as a ca. 1:1 mixture of the syn- and anti-forms. 2-Methylallyl alcohol, ethanol and propan-2-ol also induce this formal 1,2-H-atom shift in the allyloxyl radical. In the presence of ethan[H-2]ol, both 3 and (3-OD) are formed and as [EtOD] is increased from 0.3 to 3.6 mol dm(-3) [3-OD]/[3] first passes through a maximum value of ca. 1 and then decreases to 0.38. It is proposed that there is more than one mechanism for the alcohol-induced rearrangement of the allyloxyl radical, one that involves assisted migration of hydrogen from the alpha-carbon atom to the oxygen atom and another that results in incorporation of deuterium from the EtOD. The importance of the latter mechanism decreases at high alcohol concentrations and this behaviour is thought to be related to the extent of association of the alcohol by hydrogen-bonding. The allyloxyl radical was generated by UV photolysis of:allyl tert-butyl peroxide and by ring opening of the oxiranylmethyl radical, derived from epibromohydrin or epichlorohydrin by halogen-atom abstraction. Ab initio molecular orbital calculations predict that an unassisted 1,2-H-atom shift in the allyloxyl radical will involve a very large activation energy. The alcohol is believed to serve a dual function in promoting the rearrangement: first, to increase the acidity of the alpha-CH2 group by hydrogen-bonding to the oxygen atom of the allyloxyl radical and, secondly, to provide a basic oxygen atom to facilitate the transfer/removal of a protic alpha-hydrogen atom.

Abstract  Four new beta-lactam derivatives of 1,5-benzothiazepine were obtained by the reaction of 3-(3S-t-butoxyl)succinimidyl acetyl chloride with 1,5-benzothiazepines and their structures were confirmed by H-1 NMR, IR, MS techniques and elemental analysis. The other two products of this reaction were also obtained, and their structures were determined by X-ray diffraction analyses methods.

Abstract  The first iridium(I) complex containing siloxyl and N-heterocyclic carbene ligand such as [Ir(cod)(Mes)(OSiMe(3))] (1) and [Ir(CO)(2)(IMes)(OSiMe(3))] (3) have been synthesized and their structures solved by spectroscopy and X-ray methods as well as catalytic properties in selected hydrogenation reactions have been presented in comparison to their chloride analogues, i.e. [Ir(Cl)(cod)(IMes)] (2) and [Ir(Cl)(CO)(2)(IMes)] (4). The attempts at synthesis of iridium(l) complex with tert-butoxyl ligand has failed as leading instead to the iridium hydroxide complex [Ir(cod)(OH)(IMes)] (5) whose X-ray structure has also been solved. All complexes (1)-(5) show square planar geometry typical of the four-coordinated iridium complexes. Catalytic activity of complexes 1 and 2 was tested in transfer hydrogenation of acetophenone and hydrogenation of olefins. (C) 2007 Published by Elsevier B.V.

Abstract  A metal-free ring opening/halogenation of cycloalkanols, which combines both PPO/TBAX oxidant system and blue LEDs irradiation, is presented. This method produces diverse γ, δ, and even more remotely halogenated ketones in moderate to excellent yields under mild conditions. Interestingly, experimental and computational studies demonstrate the novel ring size-dependent concerted/stepwise (four-/five- to eight-membered rings) hydrogen atom transfer-electron transfer induced by Brønsted base-tethered acyloxy radical, which indicates distinct advantages brought by the cyclic structure of diacyl peroxides.

Abstract  The reactions of tert-alkyl peroxypivalates 1 (R = methyl, ethyl, and n-propyl) with styrene in the presence of the free-radical scavenger (1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yl)oxyl (2) have been studied at 60 degrees C, tert-Butyl and tert-alkoxyl radicals (tert-butoxyl, tert-pentyloxyl, and tert-hexyloxyl radicals) were generated from the thermolysis of 1, and the derivative alkyl radicals (methyl, ethyl, n-propyl, and 4-hydroxy-4-methylpentyl radicals) were formed by subsequent unimolecular reactions (beta-scission and 1,5-H shift) of the corresponding tert-alkoxyl radicals. The extent of the unimolecular reactions of the tert-alkoxyl radicals (versus addition to styrene) and the relative reactivity of alkyl radicals toward addition to styrene were obtained fi om the competitive addition/trapping reactions. The absolute rate constants for the addition of tert-butyl, ethyl, methyl, and n-propyl radicals to styrene at 60 degrees C were estimated to be (7.4, 4.7, 5, and 5.4) x 10(5) M-1 s(-1), respectively.

Abstract  A large amount of sulfuryl fluoride (SO2F2) is released into the atmosphere after fumigation, intensifying the greenhouse effect. Therefore, it is important to remove SO2F2 generated in fumigation. In this study, the solubilities of SO2F2 in 2-butoxyethyl acetate (BOEA), 3-methoxybutyl acetate (MOBA), 2-methoxyethyl acetate (MOEA), 1-methoxy-2-propyl acetate (MOPA), and 2-(2-ethoxyethoxy)ethyl acetate (DEOEA) were determined at T = (293.15 to 323.15) K and pressures up to about 600 kPa using the isochoric saturation method. Results showed that SO2F2 solubility in the five acetate derivatives increased with increasing pressure and decreased with increasing temperature. The dissolution of SO2F2 in these solvents belonged to a-physical process. Furthermore, the Henry's law constants and thermodynamic properties including standard Gibbs free energy, enthalpy, and entropy changes of SO2F2 dissolution were further obtained. Compared with water, these five selected acetate derivatives showed potential application for SO2F2 removal. Moreover, the solubilities of SO2F2 in these solvents followed the order of MOBA > MOPA > BOEA > DEOEA > MOEA.

Abstract  Electrochemical reactions are shown to be effective for the C-H functionalization of a number of heterocyclic substrates that are recalcitrant to conventional peroxide radical initiation conditions. Monitoring reaction progress under electrochemical conditions provides mechanistic insight into the C-H functionalization of a series of heterocycles of interest in medicinal chemistry.

Abstract  We explored polyurethane (PU) foaming with CO2-releasing nanoparticles from CO2 adducts of poly(propylene glycol) (PPG)-grafted polyethylenimines. The amphiphilic nature of these CO2 adduct macromolecules drives the formation of nanoparticles in the white components (i.e. foaming mixtures without isocyanates), with the hydrophobic PPG side-chains stretching outward. The outermost PPG terminal groups intimately contact the foaming mixture and thus largely determine the particle size, while the side-chain polymerization degree, ranging from 1 to 5, plays a minor role. The blowing agents with methoxyl terminal groups increased the viscosity of the white components very rapidly due to the small particles dispersed therein (e.g. 63-65 nm after 7 d aging) that caused a strong thickening effect. Normal PU foams could only be obtained within 1 h of white-component aging. Longer aging made the wall of the growing bubbles difficult to flow due to the strong thickening effect and the nanoparticles in the wall further weakened the wall while releasing CO2, both contributing to the failure of blowing. In contrast, the blowing agents with butoxyl terminal groups demonstrated a very slow increase in the viscosity and the pot life of the white components could be prolonged up to 90 d, due to the relatively large dispersed-particles (e.g. about 200 nm at aging for 60 d). The CO2 content as high as similar to 25% has been achieved in the blowing agents with the shortest side chains whose polymerization degree n =1. The PU foams obtained had densities below 50 kg/m(3) and compressive strengths over 230 kPa, both satisfying the demands of many industrial applications. (C) 2018 Published by Elsevier Ltd.

Abstract  Background Poly (ADP-ribose) polymerase (PARP) has been proposed to play an important role in the pathogenesis of heart ischaemia/reperfusion (I/R) injury. 3,4-dihydro-5[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone (DPQ), a potent PARP inhibitor, has cardiac protective effects. Because the underlying mechanisms are not understood, we investigated the effect of DPQ on heart I/R injury and its mechanisms.

Methods Studies were performed with I/R rats' hearts. DPQ was used to inhibit the activation of PARP. Cardiac function and cellular apoptosis were assessed. The activation of PARP, transcription factor nuclear factor-kappaB (NF-KB), intercellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) were evaluated. We also evaluated expression of Akt and two of its downstream targets, glycogen synthase kinase-3 beta (GSK-3 beta) and forkhead transcription factor FOX03a.

Results Administration of DPQ significantly decreased the activation of PARP and cellular apoptosis from (35 +/- 5)% to (20 +/- 4)% and simultaneously improved the cardiac function. DPQ reduced the expressions of NF-kappa B, ICAM-1, COX-2 and MMP-9 in rat heart and facilitated the activations of phosphor-Akt, phosphor-GSK-313 and phosphor-FOX03a.

Conclusion The protective effects of DPQ were associated with the suppression of inflammation and the activation of the Akt signalling pathways suggesting that the inhibition of poly (ADP-ribose) polymerase reduced heart I/R injury in rats.

Abstract  The development of a water-developable negative photoresist from beta-CD using an acid-catalyzed chemical amplification method is investigated here. Tertiary butoxyl protected beta-cyclodextrin (t-BOC-CD) is also synthesized and used to prepare a positive photoresist. Glutaraldehyde is added as a crosslinking agent for both positive and negative photoresists. Deprotection of t-BOC-CD is accelerated by a photo-induced acid. In the presence of glutaraldehyde and acid, both the deprotected t-BOC-CD and beta-cyclodextrin are crosslinked. The introduction of a t-butoxyl group into the beta-CD molecule and the addition of glutaraldehyde into the beta-CD molecules are both found to decrease the crystallinity of the molecules, improving the resist film properties. The etching resistance of both positive and negative photoresist films is improved by the crosslinking method. (C) 2008 Wiley Periodicals, Inc.

Abstract  Small molecules representing common synthetic polymers were subjected to photochemically induced hydrogen abstraction by benzophenone. Reactions were monitored using (1) H NMR to query the factors that influence preferential abstraction of protons in unique chemical environments. Differences in bond dissociation energies do not fully explain the observed hydrogen abstraction preferences. To that end, we identify contributions to abstraction from prereactive complexation, radical stability, steric effects and charge transfer effects. Using representative small molecule model compounds in lieu of polymeric materials is a novel approach to understanding photochemical reaction in polymers; however, it cannot probe the contributions of macromolecular effects--e.g. polymer rigidity or side chain and backbone mobility--to preferential hydrogen abstraction.

Abstract  In order to reveal the real intermediate in the base-promoted reaction of 1, 3-bromo-4,4-dideuterio-6,7-benaobicyclo[3.2.1]octa-2,6-diene 10 was synthesized and its HBr elimination reaction studied. Reaction of 10 with potassium tert-butoxide yielded butoxyl ether 18 in which proton-deuterium exchange has occured.

Abstract  The effect of methoxy substitution on the abstraction of the phenolic hydrogen atom involved in intramolecular hydrogen bonding by tert-butoxyl and cumyloxyl radicals has been investigated by laser flash photolysis. Also transition stale calculations for methoxyl radical and 2-methoxyphenol have been carried out by a density functional theory (DFT) method. Hydrogen atom abstraction is surprisingly easy from intramolecularly hydrogen bonded methoxyphenols, in contrast to intermolecularly hydrogen bonded molecules. The kinetic solvent effect, investigated in six solvents with different hydrogen bond accepting properties, on the hydrogen atom abstraction reaction from o-methoxy phenols was shown to be smaller than for non-hydrogen bonded phenols, and is independent of further methoxy substitution. The high rate constant for hydrogen atom abstraction from ubiqoinol-0 (2.8 x 10(9) M-1 s(-1) in CCl4) and the small kinetic solvent effect make it a good antioxidant, even in a polar environment.

Abstract  Oxidative coupling of oxime and beta-dicarbonyl compounds dominates in a beta-dicarbonyl compound/oxime/Cu(II)/t-BuOOH system; in the absence of oxime, oxidative coupling of t-BuOOH and a beta-dicarbonyl compound (Kharasch peroxidation) takes place. The proposed conditions for oxidative coupling of oximes with dicarbonyl compounds require only catalytic amounts of copper salt and t-BuOOH serves as a terminal oxidant. The C-O coupling reaction proceeds via the formation of tert-butoxyl, tert-butylperoxyl and iminoxyl radicals. Apparently, tert-butylperoxyl radicals oxidize oxime into iminoxyl radical faster than they react with beta-dicarbonyl compounds forming the Kharasch peroxidation product. Iminoxyl radicals are responsible for the formation of the target C-O coupling products; the yields are up to 77%.

Abstract  A kinetic study on the reactions of the cumyloxyl radical (CumO•) with a series of alkanols and alkanediols has been carried out. Predominant hydrogen atom transfer (HAT) from the α-C-H bonds of these substrates, activated by the presence of the OH group, is observed. The comparable kH values measured for ethanol and 1-propanol and the increase in kH measured upon going from 1,2-diols to structurally related 1,3- and 1,4-diols is indicative of β-C-H deactivation toward HAT to the electrophilic CumO•, determined by the electron-withdrawing character of the OH group. No analogous deactivation is observed for the corresponding diamines, in agreement with the weaker electron-withdrawing character of the NH2 group. The significantly lower kH values measured for reaction of CumO• with densely oxygenated methyl pyranosides as compared to cyclohexanol derivatives highlights the role of β-C-H deactivation. The contribution of torsional effects on reactivity is evidenced by the ∼2-fold increase in kH observed upon going from the trans isomers of 4- tert-butylcyclohexanol and 1,2- and 1,4-cyclohexanediol to the corresponding cis isomers. These results provide an evaluation of the role of electronic and torsional effects on HAT reactions from alcohols and diols to CumO•, uncovering moreover β-C-H deactivation as a relevant contributor in defining site selectivity.

Abstract  IBX derivative 6, synthesized in two steps from 2-aminoterephthalic acid, 8, is soluble in both DMF and water. A variety of alcohols are oxidized using 6 in DMF with ease and selectivity identical to that of parent IBX. However, oxidations carried out in water and other aqueous solvent mixtures using 6 exhibit unique selectivities toward different substrates and provide products different from reactions carried out in DMF. A mechanistic rationale is provided for this solvent dependent behavior of 6. Published by Elsevier Ltd.

Abstract  The fragmentations of three bifunctional phenylether compounds including 2-(2, 6-dichloro)phenoxyl propionitrile, N-hydroxyl-4-butoxyl phenylacetyl amine(bufexamc) and 2-(1-methylethoxyl) phenol methylcarbamate (Propoxur) under electron impact ionization were reported, Metastable ion(MI) and collision-induced dissociation(CID) at a low energy have been used to study the fragmentation pathways from molecular ions. Apart from the simple bond cleavages, and the unimolecular dissociations via ion/neutral complex intermediate as a competitive mechanism were demonstrated, Moreover, the intramolecular hydrogen transfer and double hydrogen transfers in the fragmentations of these compounds were discussed in detail.

Abstract  A variety of methods were utilized to study the mechanism of reaction of 6-iodo-5,5-dimethyl-1-hexene and its bromo, chloro, and tosylate derivatives with LDA and several other lithium dialkylamides. In the reaction of 6-iodo-5,5-dimethyl-1-hexene with LDA in THF, radical, carbanion, and carbene pathways occurred simultaneously. However, when the corresponding bromide was allowed to react with LDA, the radical pathway was minor and when the corresponding chloride or tosylate was allowed to react with LDA, no evidence for radical products was observed. This is the first time that competing radical, carbanion, and carbene pathways have been detected in the reaction of a primary alkyl halide with any nucleophile.

Abstract  The decomposition of tert-butyl hydroperoxide by photochemically induced reactions in DMSO2) and water was investigated by cw-e.s.r. spectroscopy. The products tert-butylperoxyl, methyl and sulfur-centered free radicals were identified. The tert-butoxyl free radical is involved in the primary process as shown by time-resolved e.s.r. technique. On the basis of directly identified radical species, a mechanism for the photochemically induced reactions of tert-butyl hydroperoxide in DMSO is proposed. At concentrations below 0.8 mol.l-1 the radical formation from tert-butyl hydroperoxide proceeds by cleavage of the O-O bond rather than by hydrogen abstraction.