- Merrifield resin-supported chain transfer agents, precursors for RAFT polymerization
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(Chemical Equation Presented) The modification of Merrifield resins to form chain transfer agent (CTA) precursors for reversible addition fragmentation chain transfer (RAFT) polymerization is investigated. A series of CTA precursor resins were prepared an
- Takolpuckdee, Pittaya,Mars, Craig A.,Perrier, Sebastien
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- Radical Cations of Phenoxazine and Dihydrophenazine Photoredox Catalysts and Their Role as Deactivators in Organocatalyzed Atom Transfer Radical Polymerization
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Radical cations of photoredox catalysts used in organocatalyzed atom transfer radical polymerization (O-ATRP) have been synthesized and investigated to gain insight into deactivation in O-ATRP. The stability and reactivity of these compounds were studied in two solvents, N,N-dimethylacetamide and ethyl acetate, to identify possible side reactions in O-ATRP and to investigate the ability of these radical cations to deactivate alkyl radicals. A number of other factors that could influence deactivation in O-ATRP were also probed, such as ion pairing with the radical cations, radical cation oxidation potential, and halide oxidation potential. Ultimately, these studies enabled radical cations to be employed as reagents during O-ATRP to demonstrate improvements in polymerization control with increasing radical cation concentrations. In the polymerization of acrylates, this approach enabled superior molecular weight control, a decrease in polymer dispersity from 1.90 to 1.44, and an increase in initiator efficiency from 78 to 102%. This work highlights the importance of understanding the mechanism and side reactions of O-ATRP, as well as the importance of catalyst radical cations for successful O-ATRP.
- Corbin, Daniel A.,McCarthy, Blaine G.,Van De Lindt, Zach,Miyake, Garret M.
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p. 4726 - 4738
(2021/05/29)
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- C(sp3)-H Fluorination with a Copper(II)/(III) Redox Couple
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Despite the growing interest in the synthesis of fluorinated organic compounds, few reactions are able to incorporate fluoride ions directly into alkyl C-H bonds. Here, we report the C(sp3)-H fluorination reactivity of a formally copper(III) fluoride complex. The C-H fluorination intermediate, LCuF, along with its chloride and bromide analogues, LCuCl and LCuBr, were prepared directly from halide sources with a chemical oxidant and fully characterized with single-crystal X-ray diffraction, X-ray absorption spectroscopy, UV-vis spectroscopy, and 1H nuclear magnetic resonance spectroscopy. Quantum chemical calculations reveal significant halide radical character for all complexes, suggesting their ability to initiate and terminate a C(sp3)-H halogenation sequence by sequential hydrogen atom abstraction (HAA) and radical capture. The capability of HAA by the formally copper(III) halide complexes was explored with 9,10-dihydroanthracene, revealing that LCuF exhibits rates 2 orders of magnitude higher than LCuCl and LCuBr. In contrast, all three complexes efficiently capture carbon radicals to afford C(sp3)-halogen bonds. Mechanistic investigation of radical capture with a triphenylmethyl radical revealed that LCuF proceeds through a concerted mechanism, while LCuCl and LCuBr follow a stepwise electron transfer-halide transfer pathway. The capability of LCuF to perform both hydrogen atom abstraction and radical capture was leveraged to enable fluorination of allylic and benzylic C-H bonds and α-C-H bonds of ethers at room temperature.
- Bower, Jamey K.,Cypcar, Andrew D.,Henriquez, Brenda,Stieber, S. Chantal E.,Zhang, Shiyu
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supporting information
p. 8514 - 8521
(2020/05/28)
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- Gram scale synthesis of alpha-cyanoalkylboronic esters via direct B–B and C–N bond cleavage
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A direct metal-free approach for the synthesis of alpha-cyanoalkylboronic esters from bis-diboron ester and azobis-nitrile compound is reported under ambient temperature and pressure via a free radical procedure.
- Sahoo, Sushree Ranjan,Sarkar, Debayan
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supporting information
p. 3308 - 3313
(2020/08/06)
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- Radical-triggered three-component coupling reaction of alkenylboronates, α-halocarbonyl compounds, and organolithium reagents: The inverse ylid mechanism
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An operationally simple protocol to affect a radical addition to alkenylboronates that spontaneously undergo a [1,2]-metalate shift is described. Overall, the reaction is a three-component coupling of an organolithium, alkenylboronic ester, and halide which takes place with broad scope and good to excellent yields. Experimental mechanistic investigations support the formation of a boron inverse ylid intermediate.
- Tappin, Nicholas D. C.,Gn-Gi-lux, Manuel,Renaud, Philippe
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supporting information
p. 11498 - 11502
(2018/10/21)
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- S-IMINO-S-OXO IMINOTHIAZINE COMPOUNDS AS BACE INHIBITORS, COMPOSITIONS, AND THEIR USE
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In its many embodiments, the present invention provides certain C-6 spirocarbocyclic iminothiadiazine compounds, including compounds Formula (I): or a tautomer thereof, and pharmaceutically acceptable salts of said compounds and said tautomers, wherein R1A, R1B, R2A, R2B, R2, R3, RN, ring A, RA, m, ring B, RB, and n are as defined herein. The novel compounds of the invention are useful as BACE inhibitors and/or for the treatment and prevention of various pathologies related thereto. Pharmaceutical compositions comprising one or more such compounds (alone and in combination with one or more other active agents), and methods for their preparation and use, including for the possible treatment of Alzheimer's disease, are also disclosed.
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Page/Page column 40
(2016/06/01)
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- S-IMINO-S-OXO IMINOTHIAZINE COMPOUNDS AS BACE INHIBITORS, COMPOSITIONS, AND THEIR USE
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In its many embodiments, the present invention provides provides certain S-imino-S-oxo iminothiazine compounds, including compounds Formula (I): or a tautomers and/or stereoisomers thereof, and pharmaceutically acceptable salts of said compounds, said tautomeros and said stereoisomers, wherein RN, R1A, R1B, R2, R3, R4, ring A, RA, m, L1-, and RL are as defined herein. The novel compounds of the invention are useful as BACE inhibitors and may be useful for the treatment and prevention of various pathologies related thereto. Pharmaceutical compositions comprising one or more such compounds (alone and in combination with one or more other active agents), and methods for their preparation and use, including for the possible treatment of Alzheimer's disease, are also disclosed.
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Page/Page column 62
(2014/10/04)
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- NOVEL CHAIN TRANSFER AGENT AND EMULSION POLYMERIZATION USING THE SAME
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To provide a novel compound having both a surface-activating ability and a polymerization controlling ability. A compound represented by the following general formula (1) or (2): wherein, R1 and R3 are an organic group having the hyd
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Page/Page column 13-14
(2012/12/14)
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- Process for the production of living radical polymers and polymers
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A process for producing a living radical polymer characterized in that a vinyl monomer is polymerized with use of an organotellurium compound represented by the formula (1) and an azo type polymerization initiator, and the living radical polymer obtainable by the process wherein R1 is C1-C8 alkyl, aryl, substituted aryl or an aromatic heterocyclic group, R2 and R3 are each a hydrogen atom or C1-C8 alkyl, and R4 is aryl, substituted aryl, an aromatic heterocyclic group, acyl, oxycarbonyl or cyano.
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Page/Page column 7
(2008/06/13)
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- An improved preparation of enamines of acylsilanes, a new synthesis of acylsilanes
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The use as solvent of hexamethylphosphortriamide instead of the previously used tetrahydrofuran has allowed the synthesis in high yield of enamines of acylsilanes (2) from cyanohydrins (1) by reductive silylation with Me3SiCl/Li.Protodesilylation of 2a (R = R' = Me) by HCl has in dry diethyl ether or by trimethylchlorosilane in methanol gave, after neutralization, a quantitative yield of the enamine Me2C=C(SiMe3)NH2, which was surprisingly stable.Its ready hydrolysis to the corresponding acylsilane provided a new route to this type of compound.Reaction of bromine with 2a gave α-bromoisobutyronitrile.
- Picard, J. P.,Aizpurua, J. M.,Elyusufi, A.,Kowalski, P.
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- Reaction of Arenesulphonyl Halides with Free Radicals. Part 3.
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The decomposition of azoisobutyronitrile (AIBN) and t-butyl phenylperacetate in the presence of toluene-p-sulphonyl bromide and iodide were studied; results are explained on the basis of free radical reactions.The relative reactivities of several alkane- and arene-sulphonyl chlorides towards phenyl, benzyl, and trichloromethyl radicals were measured in competition experiments.Results are rationalized on the grounds of a balance between polar effects in the initial and in the transition state.
- da Silva Correa, Carlos M.M.,Oliveira, Maria Augusta B.C.S.
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p. 811 - 814
(2007/10/02)
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- (2-Cyanoallyl)trimethylsilane and (2-Cyanoethyl)trimethylsilane. Unique ?? Captodative Systems
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Addition reactions of (2-cyanoallyl)trimethylsilane as well as hydrogen abstraction reactions of (2-cyanoethyl)trimethylsilane were examined.These compounds exhibit high reactivities in free-radical reactions, demonstrating existence of the ?? captodative effect.
- Sakurai, Hideki,Kyushin, Soichiro,Nakadaira, Yasuhiro
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p. 297 - 300
(2007/10/02)
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