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.

Abstract  A solution-processable double-cable polymer (PFT-PDI), composed of the backbone poly(fluorene-alt-hiophene) (PFT), the n-butoxyl linker, and the pendants perylenediimides (PDI), was developed. PFT-PDI was almost nonconductive with the hole and electron mobilities in the order of 10(-10). There was no charge transfer but energy transfer from the donor PFT chain to the acceptor PDI units. With a hole-transporting channel from the stacked PFT units and an electron-transporting channel along PDI chain, PFTPDI at the P3HT/PCBM interface facilitated the effective charge generation from P3HT excitons and charge transporting and enhanced the cell photocurrent. The encapsulated cell ITO/MoO/P3HT:PCBM:PFT-PDI/LiF/Al with doping PFT-PDI of 3 wt % demonstrated the maximum power conversion efficiency (PCE) of 4.50%, increasing by 27.5%, relative to PCE of 3.53% from the cell without doping. The PFT-PDI doping much improved the cell's stability with the loss of the initial PCE of 5.8%, in contrast to 29.7% from the reference device after being stored for 7 days.

Abstract  Six neopentyl esters have been selected, as models for pentaerythrityl esters used as lubricants, to study the selectivity of hydrogen abstraction by alkoxyl radicals. Kinetic and product data for the reactions of two oxygenated radicals, tert-butoxyl and cumyloxyl, with the six neopentyl esters between 408 and 438 K have been determined. They show that attack by the radicals occurs at the alpha- and subsequent positions on the acyl moiety as well as at the alkyl group. The selectivity of the reactions is discussed in terms of bond dissociation, steric and polar effects.

Abstract  The reaction enthalpies for the recombination of carbon-centered radicals, R, with molecular oxygen have been established by photoacoustic calorimetry (PAC) in the liquid phase and by means of density functional theory calculations (DFT) with the B3LYP functionals and the 6-31(d) basis set. The experimental study revealed the following carbon-oxygen bond dissociation enthalpies, BDE(R-OO) (kcal mol(-1)): cyclohexadienyl (12), 1-tetrahydrofuryl (32), and dioxanyl (34). For 1-triethylaminyl and 1-pyrrolidinyl, the reaction enthalpy suggests that in organic solvents disproportionation becomes important even within the first stage of the reaction. DFT underestimates the BDE(R-OO) by 0-6 kcal mol(-1). However, DFT BDE(R-H)BDE(R-OO) are in accordance with experimental data. The computed BDE(R-OO) is not sensitive to substitution by alkyl groups.

Abstract  Using competition kinetic methodology, absolute rate constants for bimolecular hydrogen abstraction from a variety of organic substrates in solution have been obtained for the n-C4H9CF2CF2., n-C4F9., and i-C3F7. radicals. Fluorine substitution substantially increases the reactivity of alkyl radicals with respect to C-H abstraction, with the secondary radical being most reactive. A wide range of substrate reactivities (5200-fold) was observed, with the results being discussed in terms of an interplay of thermodynamic, polar, steric, stereoelectronic, and electrostatic/field effects on the various C-H abstraction transition states. Representative carbon-hydrogen bond dissociation energies of a number of ethers and alcohols have been calculated using DFT methodology.

Abstract  Standard computational models of cytotoxicity of substituted phenols relate the toxicity to a set of quatitative structure-activity relationship (QSAR) descriptors such as log P, p K a, OH bond dissociation enthalpy (BDE), etc. Implicit in this approach is the idea that the phenoxyl radical is disruptive to the cell and factors increasing its production rate will enhance the toxicity. To improve the QSAR correlations, substituents are usually divided into electron-donating groups (EDG) and electron-withdrawing groups (EWG), which are treated separately and thought to follow different mechanisms of toxicity. In this paper, we focus on one important aspect of toxicity, the rate constant for production of phenoxyl radical. Activation energies are obtained for the reaction of X-phenol with peroxyl radical by using the Evans-Polanyi principle, giving rate constants as a function of DeltaBDE values for both EDG and EWG sets. We show that (i) a plot of log k for phenoxyl formation vs DeltaBDE shows a double set of straight lines with different slopes, justifying the usual EDG and EWG separation but without requiring any change in mechanism; (ii) the same method can be effectively used for different target radicals (e.g., tert-butoxyl) or different sets of parent compounds (e.g., substituted catechols), thus giving a useful general approach to analysis of toxicity data; (iii) regions of constant toxicity in all cases are predicted; and (iv) we argue that competing parallel mechanisms of toxicity are likely to be dominant for EWG-substituted phenols.

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  Abstract: Principal component analysis (PCA) was performed on experimental rate constant and theoretical barrier height data of radical addition reactions involving various carbon- and sulfur-centered radicals and vinyl-type alkenes. Altogether six data sets were analyzed. In three cases the reactivity data were completed by certain descriptors, i.e., the electron affinity (EA) and negative ionization potential (-IP) of alkenes, as well as the exothermicity (-Delta H(r)) of reactions. It was found that in each case the first two principal components account for more than 93% of the total variance in the data. The scores of the first principal component correlate with EA and (-Delta H(r)), whereas those of the second principal component with (-IP). It is concluded that PCA is able to decompose both experimental and theoretical reactivity data into nucleophilic and electrophilic components, as well as into polar and enthalpy terms. In the plots of component loadings the radicals form significant groups depending on their character. Thus, PCA can classify radicals according to nucleophilicity and electrophilicity. The PCA results were validated by significant correlations of experimental and theoretical reactivity data with Hammett sigma(p) as well as with the descriptors EA, (-Delta H(r)), and (-IP). The hydroxymethyl radical is classified as strongly nucleophilic, the methyl radical as moderately nucleophilic, the tert-butoxycarbonylmethyl and cyanomethyl radicals as weakly nucleophilic, the phenylsulfonyl and tosyl radicals as moderately electrophilic, and the 2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl radical as strongly electrophilic. It is concluded that the reactivities of tert-butoxycarbonylmethyl and cyanomethyl radicals are mainly governed by enthalpy effects. This conclusion is in agreement with the findings of Giese et al. [Chem. Ber. 1988, 121, 2063-2066] and Fischer et al. [Helv. Chim. Acta 1995, 78, 194-214]. A symmetry pattern of correlations is proposed: the reactivity correlates with EA for strongly nucleophilic radicals, with EA and (-Delta H(r)) for moderately nucleophilic radicals, with (-Delta H(r)) for weakly nucleophilic or weakly electrophilic radicals, with (-Delta H(r)) and (-IP) for moderately electrophilic radicals, and with (-IP) for strongly electrophilic radicals. On the basis of the symmetry pattern of correlations, it is concluded that the dominant factors influencing radical addition reactions are polar effects alone for strongly nucleophilic or strongly electrophilic radicals, polar and enthalpy effects for moderately nucleophilic or moderately electrophilic radicals, and enthalpy effects alone for weakly nucleophilic or weakly electrophilic radicals. ds: Chemistry cument Delivery No.: 145MV e field[29]: 1,4-Dioxane

Abstract  Abstract: A comparison of the tris(trimethylsilyl)silyl I and tris(trimethylsilyl)germyl II radical reactivity is provided. Their formation as well as their reactivity encountered in a large variety of chemical processes (addition to double bond, halogen abstraction, peroxyl radical formation…) is examined by laser flash photolysis, quantum mechanical calculations and electron spin resonance (ESR) experiments. The starting compound (TMS)3GeH is more reactive than (TMS)3SiH toward the t-butoxyl, the t-butylperoxyl and the phosphinoyl radicals. A similar behavior is noted for an aromatic ketone triplet state. II exhibits a lower absolute electronegativity: accordingly, the addition to electron rich alkenes is less efficient than for I. Radical II is also found less reactive for both the peroxylation and the halogen abstraction reactions. The rearrangement of is slower than for ; this is related to the respective exothermicity of the processes. [Copyright 2008 Elsevier] Copyright of Journal of Organometallic Chemistry is the property of Elsevier Science Publishers B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts)

Abstract  In our effort to develop selective sphingosine kinase-2 (SphK2) inhibitors as pharmacological tools, a thiazolidine-2,4-dione analogue, 3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145), was synthesized and biologically characterized. Biochemical assay results indicate that K145 is a selective SphK2 inhibitor. Molecular modeling studies also support this notion. In vitro studies using human leukemia U937 cells demonstrated that K145 accumulates in U937 cells, suppresses the S1P level, and inhibits SphK2. K145 also exhibited inhibitory effects on the growth of U937 cells as well as apoptotic effects in U937 cells, and that these effects may be through the inhibition of down-stream ERK and Akt signaling pathways. K145 also significantly inhibited the growth of U937 tumors in nude mice by both intraperitoneal and oral administration, thus demonstrating its in vivo efficacy as a potential lead anticancer agent. The antitumor activity of K145 was also confirmed in a syngeneic mouse model by implanting murine breast cancer JC cells in BALB/c mice. Collectively, these results strongly encourage further optimization of K145 as a novel lead compound for development of more potent and selective SphK2 inhibitors.

Abstract  The consumption rates of three monolignols (p-coumaryl, coniferyl, and sinapyl alcohols) and eight analogues using horseradish peroxidase (HRP)-H2O2 as an oxidant were measured and compared with the anodic peak potentials thereof measured with cyclic voltammetry. 3-Monosubstituted p-coumaryl alcohols, i.e., 3-methoxy-, 3-ethoxy-, 3-n-propoxy-, and 3-n-butoxy-p-coumaryl alcohols, had faster reaction rates than p-coumaryl alcohol. This is most probably due to the electron-donating effect of alkoxyl groups. However, the reaction rates gradually decreased with an increase in the molecular weight of the alkoxyl groups. Furthermore, t-butoxyl group, which is a very bulky substituent, caused an extreme reduction in the reaction rate, even though its electron-donating effect was almost the same as that of other alkoxyl groups. The reaction rates of 3,5-disubstituted p-coumaryl alcohols, especially 3,5-dimethyl-p-coumaryl alcohol, were very low compared with 3-monosubstituted p-coumaryl alcohols. These results suggest that there are three main factors of hindrance during the approach of monolignols to the active site of HRP. First, from the results of 3-monoalkoxy-p-coumaryl alcohols, it was suggested that the volume of substituents could decrease their oxidation rates. Second, from the results of 3,5-disubstituted p-coumaryl alcohols, it was suggested that local steric hindrance by the amino residues quite near the heme decreased the oxidation rates. Third, from the results of the substrates with hydrophobic substituents at their 3,5-positions, we suggested that hydrophilicity near heme would decrease their oxidation rates.

Abstract  3-(3-t-Butoxyl)succinimidyl acetyl chloride was obtained by a series of reactions starting from malic acid. 3-(3-t-Butoxyl)succinimidyl acetyl chloride reacted with Schiff bases 1a similar to 1h to yield 8 new 3-(3-t-butoxyl)succinimidyl monocyclic P-lactam derivatives 2a similar to 2h. The structures of the new compounds were confirmed by IR, H-1 NMR, MS spectra and elemental analysis.

Abstract  A simple method for the preparation of 5-epi-nojirymycin (5-epi-DNJ) by a reductive amination of sugar derived alkoxyamines is presented. The latter were prepared in situ from the respective alkylated sugar oximes, which were obtained from the readily available methyl alpha-D-glucoside in a few well defined steps. The stereoselectivity of the reductive amination/cyclisation step depended on the size of the alkyl group in the oxime moiety and was best for the derivative decorated with a bulky tert-butoxyl group (5-epi-DNJ:DNJ = 82:18). The stereochemical outcome of this reaction was rather surprising since the analogous process performed for sugar alkylamines usually provides predominantly derivatives of DNJ. (C) 2016 Elsevier Ltd. All rights reserved.

Abstract  A kinetic study on the effect of acetic (AcOH) and trifluoroacetic acid (TFA) on hydrogen abstractions from the C-H bonds of basic substrates by the cumyloxyl radical (CumO(center dot)) was carried out in acetonitrile. With tetrahydropyran no significant effect on k(H) was observed after acid addition. With the more basic tertiary amines acid addition led to greater than 4-orders of magnitude decreases in k(H). Protonation at nitrogen decreases the degree of overlap between the alpha-C-H sigma* orbital and the lone-pair leading to an increase in the strength of the C-H bond and a destabilization of the radical formed after abstraction. Evidence that C-H deactivation extends up to the gamma-C-H bonds and for the reversibility of this approach was also provided. With TFA no reaction was observed up to [amine] = [TFA], pointing towards stoichiometric protonation. At [amine] > [TFA], k(H) values that are very similar to those measured in the absence of added acid were obtained. With the weaker acid, AcOH, no reaction was observed up to [AcOH]/[amine] similar to 4, and a curved plot was observed with increasing [amine], as a result of the acid-base equilibrium between AcOH and the amine. With 1,4-dimethylpiperazine, a quantitative evaluation of the C-H deactivation determined by sequential protonation of one or both nitrogen centers was obtained. These observations show that protonation provides an extremely efficient, precise and tunable method for the deactivation of the C-H bonds of basic substrates allowing moreover for careful control over the hydrogen abstraction selectivity. The implications of this approach are discussed.