- Decarboxylative Bromination of Sterically Hindered Carboxylic Acids with Hypervalent Iodine(III) Reagents
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Sterically hindered three-dimensional (3D) alkyl halides are promising precursors for various reactions; however, they are difficult to synthesize via conventional reactions. We present an efficient and practical method for decarboxylative bromination of sterically hindered 3D aliphatic carboxylic acids using commercially available (diacetoxyiodo)benzene and potassium bromide, one of the most stable and cheapest bromine sources in nature. The present method features a metal-free/Br2-free system, mild reaction conditions, one-pot operation under air at room temperature, wide functional group compatibility, and gram-scale synthetic capability. This highly efficient reaction cleanly converts a broad range of carboxylic acids, the most inexpensive and readily available sources of highly strained/naturally occurring/drug-related scaffolds, into the corresponding alkyl bromides in good to high yields.
- Kanazawa, Junichiro,Koyamada, Kenta,Miyamoto, Kazunori,Uchiyama, Masanobu,Watanabe, Ayumi
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supporting information
p. 1328 - 1334
(2020/08/14)
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- Dual copper- and photoredox-catalysed C(sp2)-C(sp3) coupling
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The use of copper catalysis with visible light photoredox catalysis in a cooperative fashion has recently emerged as a versatile means of developing new C-C bond forming reactions. In this work, dual copper and photoredox catalysis is exploited to effect C(sp2)-C(sp3) cross-couplings between aryl boronic acids and benzyl bromides.
- McLean, Euan B.,Gauchot, Vincent,Brunen, Sebastian,Burns, David J.,Lee, Ai-Lan
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supporting information
p. 4238 - 4241
(2019/04/30)
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- In Situ Generated Gold Nanoparticles on Active Carbon as Reusable Highly Efficient Catalysts for a Csp3 ?Csp3 Stille Coupling
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Gold nanoparticle catalysts are important in many industrial production processes. Nevertheless, for traditional Csp2-Csp2 cross-coupling reactions they have been rarely used and Pd catalysts usually give a superior performance. Herein we report that in situ formed gold metal nanoparticles are highly active catalysts for the cross coupling of allylstannanes and activated alkylbromides to form Csp3-Csp3 bonds. Turnover numbers up to 29 000 could be achieved in the presence of active carbon as solid support, which allowed for convenient catalyst recovery and reuse. The present study is a rare case where a gold metal catalyst is superior to Pd catalysts in a cross-coupling reaction of an organic halide and an organometallic reagent.
- Holz, Julia,Pfeffer, Camilla,Zuo, Hualiang,Beierlein, Dennis,Richter, Gunther,Klemm, Elias,Peters, René
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p. 10330 - 10334
(2019/06/27)
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- Visible-Light-Driven Oxidative Mono- and Dibromination of Benzylic sp 3 C-H Bonds with Potassium Bromide/Oxone at Room Temperature
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Benzylic sp 3 C-H bonds have been successfully brominated with potassium bromide by using Oxone as an oxidant in water/dichloromethane under visible light at room temperature. Toluene, ethylbenzene and other alkylbenzenes bearing an electron-withdrawing group, such as Br, Cl, COMe, CO 2 Et, CO 2 H, CN or NO 2, provide the corresponding benzylic monobromides in good to excellent yields in this reaction. Dibromides can also be produced in the presence of excess potassium bromide in a prolonged reaction time. Control of the illuminance of visible light (~500 lux) is crucial to achieving both high yield and high selectivity in these brominations. Mono- and difluorides can be conveniently prepared through nucleophilic substitutions of the benzylic bromides with potassium fluoride.
- Zhao, Mengdi,Li, Meiqi,Lu, Wenjun
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supporting information
p. 4933 - 4939
(2018/12/14)
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- Scalable anti-Markovnikov hydrobromination of aliphatic and aromatic olefins
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To improve access to a key synthetic intermediate we targeted a direct hydrobromination-Negishi route. Unsurprisingly, the anti-Markovnikov addition of HBr to estragole in the presence of AIBN proved successful. However, even in the absence of an added initiator, anti-Markovnikov addition was observed. Re-examination of early reports revealed that selective Markovnikov addition, often simply termed "normal" addition, is not always observed with HBr unless air is excluded, leading to the rediscovery of a reproducible and scalable initiator-free protocol.
- Galli, Marzia,Fletcher, Catherine J.,Del Pozo, Marc,Goldup, Stephen M.
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supporting information
p. 5622 - 5626
(2016/07/06)
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- Direct and selective benzylic oxidation of alkylarenes via C-H abstraction using alkali metal bromides
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A direct benzylic oxidation of alkylarenes via C-H bond abstraction was developed using alkali metal bromides and oxidants under mild conditions. This reaction proceeded with excellent selectivity by thermal oxidation or photooxidation to provide a broad range of carbonyl compounds containing electron-deficient aryl carbonyl compounds in high yields.
- Moriyama, Katsuhiko,Takemura, Misato,Togo, Hideo
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supporting information; experimental part
p. 2414 - 2417
(2012/06/18)
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- Oxidation of benzylic methylenes to ketones with Oxone-KBr in aqueous acetonitrile under transition metal free conditions
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A green and highly efficient protocol for the oxidation of benzylic methylenes to their corresponding ketones with a combination of Oxone and KBr in aqueous acetonitrile is developed. The H218O labeling experiment demonstrated that the oxygen introduced into ketone originated from water. A plausible mechanism was also suggested.
- Yin, Lixia,Wu, Jingjing,Xiao, Juan,Cao, Song
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supporting information; experimental part
p. 4418 - 4421
(2012/09/25)
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- (R)-3-(N,N-DIMETHYLAMINO)PYRROLIDINE DERIVATIVES
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(R)-3-(N,N-Dimethyiamino)pyrrolidine derivatives of formula (I), wherein the meaning for Cy1 is as disclosed in the description. These compounds are useful as JAK3 kinase inhibitors
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Page/Page column 87
(2010/04/27)
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- PYRAZOLE DERIVATIVES AS ANTI-PLATELET AND ANTI-THROMBOTIC AGENTS
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This invention relates to novel compounds of formula (I) or stereoisomers or pharmaceutically acceptable salts thereof wherein Y, R1 through R9, and X1 through X7 are as defined in the specification, pharmaceutical compositions containing said compounds useful as P2Y1 antagonists, and to methods of treating thromboembolic disorders.
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Page/Page column 57
(2010/11/30)
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- Pyrimidinedione derivatives and antiarrythmic agents containing the same
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A pyrimidinedione derivative compound has a basic backbone in which a phenyl group part and a pyrimidinedione part are linked by a linking structure comprising an alkyl chain containing two nitrogen atoms. This linking structure is represented by STR1 [wherein A is --(CH2)n --, --CO-- or --O--(CH2)m --; each of R1 and R2 is independently a hydrogen atom or a lower alkyl group which may be substituted by a hydroxyl group, or R1 and R2 may be so linked with each other as to make an alkylene chain and thus form a heterocyclic structure; R5 is a halogen atom, a hydroxyl group, a lower alkyloxycarbonyl group, a lower alkyloxy group which may be substituted by a lower alkyloxy group, or a lower alkyl group which may be substituted by a hydroxyl group, or R5 may be so linked with R1 as to make an alkylene chain and thus form a heterocyclic structure; n is 0, 1, 2 or 3 (when R5 is the hydroxyl group, n≠0); m is 0, 1, 2 or 3; and k is 0, 1, 2 or 3 (however, a compound in which A is --O--(CH2)m -- and R5 is the hydroxyl group is excluded from the pyrimidinedione derivative)]. The pyrimidinedione derivative and its acid addition salt are useful for a medical treatment of cardiac arrhythmias.
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- Chemical compounds
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A novel class of protecting compounds, particularly for amino acids, is based on 2,2 di nitrophenyl ethan- groups, particularly the groups wherein the nitro is in the para position. The ethyl group may be substituted, e.g. by an alkyl group, in the l- position. Preferred compounds include the alcohol or halide which are suitable for protecting acid functional groups, and esters, including activated and substituted esters, particularly the succinimidyl ester, for protecting amine groups. The invention includes methods of manufacture and use, together with protected amino acids.
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- The ion-pair mechanism and bimolecular displacement at saturated carbon. VI. Razemization and radio-bromide exchange for substituted 1-phenylbromoethanes; solvent effects
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Racemization and radio-bromide exchange kinetics for 1-phenylbromoethanes in acetonitrile and in nitromethane using tetrabutylammonium bromide are reported.The results, together with those previously reported for acetone solutions, provide direct empirical support for the ion-pair mechanism for nucleophilic substitution at saturated carbon.Changing the substituents on the phenyl from the 4-nitro through to the 3,4-dimethyl substrate and the solvent from acetone to the more polar acetonitrile and nitromethane shifts the transition state for bromide substitution from an early to a late stage of the equilibria series substrate intimate ion pair various solvated ion pairs free or dissociated ions.For all the substrates in acetone and, for the species giving the less stable carbocations, in acetonitrile and nitromethane, both racemizations and exchanges are bimolecular.In the latter solvents, the substrates giving the more stable carbocations show mixed kinetics.
- Stein, Allan R.
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p. 363 - 371
(2007/10/02)
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- Synthesis of 3-Phenoxybenzyl 3-Alkyl-3-phenyl-/p-substituted phenyl and 3-Phenoxybenzyl 2-Alkyl-3-phenyl-/p-substituted phenylpropionates
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Some 3-phenoxybenzyl 3-alkyl-3-phenyl-/p-substituted phenylpropionates (VII, XI, XV, XIX, XXIII, XXVII) which resemble structurally the 1,2-secopyrethroids, have been prepared employing simple reactions like alkylation, decarbethoxylation and transesterification.The synthesis of 3-phenoxybenzyl 2-alkyl-3-phenyl-/p-substituted phenyl-propionates (XXXI, XXXII, XXXIII, and XXXVI) bearing close structural resemblance to 2,3-secopyrethroids has also been described.
- Kelkar, S. V.,Joshi, G. S.,Kulkarni, G. H.,Mitra, R. B.
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- Preparation of chiral 1-phenylethanols and bromides
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A fast, convenient procedure for preparing and resolving moderate to large quantities of chiral secondary alcohols is described.The general procedure involves a one-pot conversion of the ketone (various acetophenones) to the half-ester of a diacid (succinic, phthalic...) and resolution with (+)- and (-)-1-phenylethylamines.Overall yields of the enantiomeric alcohols, the variously substituted 1-phenylethanols, are generally 65-85percent with optical purities of approximately 90percent.Properties and optical rotations of a number of chiral 1-phenylethanols and of the bromides made from them are tabulated.A discussion of optical purity determinations using nmr methods is included and absolute configurations are reported.
- Stein, Allan R.,Dawe, Robert D.,Sweet, James R.
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p. 3442 - 3448
(2007/10/02)
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- INTRAMOLECULAR ELECTRON TRANSFER AND DEHALOGENATION OF NITROAROMATIC ANION RADICALS.
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A series of nitroaromatic compounds, containing Cl, Br or tosyl groups at various positions, were synthesized and studied by pulse radiolysis in aqueous alcohol solutions. One-electron reduction of the compounds produces the anion radicals which then undergo an intramolecular electron transfer and eliminate X** minus (Cl** minus , Br** minus , or TsO** minus ). The rates of X** minus elimination vary over six orders of magnitude and are affected by the C-X bond dissociation energies, the size and nature of the group bridging the X with the pi system, and the relative positions of these groups. Intramolecular electron transfer through space is also demonstrated. Refs.
- Bays,Blumer,Baral-Tosh,Behar,Neta
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p. 320 - 324
(2007/10/02)
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