- Radical Chain Reduction via Carbon Dioxide Radical Anion (CO2?-)
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We developed an effective method for reductive radical formation that utilizes the radical anion of carbon dioxide (CO2?-) as a powerful single electron reductant. Through a polarity matched hydrogen atom transfer (HAT) between an electrophilic radical and a formate salt, CO2?- formation occurs as a key element in a new radical chain reaction. Here, radical chain initiation can be performed through photochemical or thermal means, and we illustrate the ability of this approach to accomplish reductive activation of a range of substrate classes. Specifically, we employed this strategy in the intermolecular hydroarylation of unactivated alkenes with (hetero)aryl chlorides/bromides, radical deamination of arylammonium salts, aliphatic ketyl radical formation, and sulfonamide cleavage. We show that the reactivity of CO2?- with electron-poor olefins results in either single electron reduction or alkene hydrocarboxylation, where substrate reduction potentials can be utilized to predict reaction outcome.
- Hendy, Cecilia M.,Smith, Gavin C.,Xu, Zihao,Lian, Tianquan,Jui, Nathan T.
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supporting information
p. 8987 - 8992
(2021/07/01)
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- Palladium-Catalyzed Chlorocarbonylation of Aryl (Pseudo)Halides Through In Situ Generation of Carbon Monoxide
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An efficient palladium-catalyzed chlorocarbonylation of aryl (pseudo)halides that gives access to a wide range of carboxylic acid derivatives has been developed. The use of butyryl chloride as a combined CO and Cl source eludes the need for toxic, gaseous carbon monoxide, thus facilitating the synthesis of high-value products from readily available aryl (pseudo)halides. The combination of palladium(0), Xantphos, and an amine base is essential to promote this broadly applicable catalytic reaction. Overall, this reaction provides access to a great variety of carbonyl-containing products through in situ transformation of the generated aroyl chloride. Combined experimental and computational studies support a reaction mechanism involving in situ generation of CO.
- Bismuto, Alessandro,Boehm, Philip,Morandi, Bill,Roediger, Sven
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supporting information
p. 17887 - 17896
(2020/08/19)
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- Para-Selective C-H Olefination of Aniline Derivatives via Pd/S,O-Ligand Catalysis
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Herein we report a highly para-selective C-H olefination of aniline derivatives by a Pd/S,O-ligand-based catalyst. The reaction proceeds under mild reaction conditions with high efficiency and broad substrate scope, including mono-, di-, and trisubstituted tertiary, secondary, and primary anilines. The S,O-ligand is responsible for the dramatic improvements in substrate scope and the high para-selectivity observed. This methodology is operationally simple, scalable, and can be performed under aerobic conditions.
- Naksomboon, Kananat,Poater, Jordi,Bickelhaupt, F. Matthias,Fernández-Ibá?ez, M. ángeles
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supporting information
p. 6719 - 6725
(2019/05/06)
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- Dehydrogenative cross-coupling of primary alcohols to form cross-esters catalyzed by a manganese pincer complex
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Base-metal-catalyzed dehydrogenative cross-coupling of primary alcohols to form cross-esters as major products, liberating hydrogen gas, is reported. The reaction is catalyzed by a pincer complex of earth-abundant manganese in the presence of catalytic base, without any hydrogen acceptor or oxidant. Mechanistic insight indicates that a dearomatized complex is the actual catalyst, and indeed this independently prepared dearomatized complex catalyzes the reaction under neutral conditions.
- Das, Uttam Kumar,Ben-David, Yehoshoa,Leitus, Gregory,Diskin-Posner, Yael,Milstein, David
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p. 479 - 484
(2019/01/11)
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- Synthesis of Halogenated Anilines by Treatment of N, N-Dialkylaniline N-Oxides with Thionyl Halides
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The special reactivity of N,N-dialkylaniline N-oxides allows practical and convenient access to electron-rich aryl halides. A complementary pair of reaction protocols allow for the selective para-bromination or ortho-chlorination of N,N-dialkylanilines in up to 69% isolated yield. The generation of a diverse array of halogenated anilines is made possible by a temporary oxidation level increase of N,N-dialkylanilines to the corresponding N,N-dialkylaniline N-oxides and the excision of the resultant weak N-O bond via treatment with thionyl bromide or thionyl chloride at low temperature.
- Reed, Hayley,Paul, Tyler R.,Chain, William J.
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p. 11359 - 11368
(2018/08/06)
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- Conversion of alcohols to alkyl esters and carboxylic acids using heterogeneous palladium-based catalysts
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Disclosed are methods for synthesizing an ester or a carboxylic acid from an organic alcohol. To form the ester one reacts, in the presence of oxygen gas, the alcohol with methanol or ethanol. This reaction occurs in the presence of a catalyst comprising palladium and a co-catalyst comprising bismuth, tellurium, lead, cerium, titanium, zinc and/or niobium (most preferably at least bismuth and tellurium). Alternatively that catalyst can be used to generate an acid from that alcohol, when water is also added to the reaction mix.
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- Direct oxidative cyanation of tertiary amines promoted by in situ generated hypervalent iodine(III)-CN intermediate
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An environmentally benign and metal-free cyanation method of tertiary amines oxidated by hypervalent iodine(III) intermediate generated in situ from PIFA (or DIB) and TMSCN has been developed. A variety of substituent groups on amines are tolerated to the oxidation of α-C-H bond to form C-C bond in the absence of metal catalysts with yields of up to 74%.
- Shen, Hang,Zhang, Xiaohui,Liu, Qing,Pan, Jing,Hu, Wen,Xiong, Yan,Zhu, Xiangming
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supporting information
p. 5628 - 5631
(2015/09/21)
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- Ultrasound-Assisted Methyl Esterification of Carboxylic Acids ACatalyzed by Polymer-Supported Triphenylphosphine
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A convenient and efficient sonochemical method for methyl esterification of carboxylic acids catalyzed by polymer-supported triAphenylphosphine (PS-Ph3P) is reported. In the presence of 1:0.1:2 molar ratio of 2,4,6-trichloro-1,3,5-triazine/PS-Ph3P/Na2CO3, methyl esters of various carboxylic acids bearing reactive hydroxyl groups as well as acid-or base-labile functionalities could be rapidly prepared (within 10-20 min) in good to excellent yields without necessity to pre-activate the acids. Using the polymer-bound phosphine also allows easy isolation of the products which, in most of the cases, were obtained in high purities without column chromatography.
- Jaita, Subin,Phakhodee, Wong,Pattarawarapan, Mookda
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p. 2006 - 2008
(2015/09/01)
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- Metal-free functionalization of N, N-dialkylanilines via temporary oxidation to N, N-dialkylaniline N-oxides and group transfer
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A simple set of protocols for the controlled elaboration of anilines is reported allowing access to a diverse array of aminophenols, aminoarylsulfonates, alkylated anilines, and aminoanilines in 29-95% yield in a single laboratory operation from easily isolable, bench-stable N,N-dialkylaniline N-oxides. The introduction of new C-O, C-C, and C-N bonds on the aromatic ring is made possible by a temporary increase in oxidation level and excision of a weak N-O bond.
- Lewis, Robert S.,Wisthoff, Michael F.,Grissmerson,Chain, William J.
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supporting information
p. 3832 - 3835
(2014/08/05)
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- Aerobic oxidation of diverse primary alcohols to methyl esters with a readily accessible heterogeneous Pd/Bi/Te catalyst
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Efficient aerobic oxidative methyl esterification of primary alcohols has been achieved with a heterogeneous catalyst consisting of 1 mol % Pd/charcoal (5 wt %) in combination with bismuth(III) nitrate and tellurium metal. The Bi and Te additives significantly increase the reaction rate, selectivity, and overall product yields. This readily accessible catalyst system exhibits a broad substrate scope and is effective with both activated (benzylic) and unactivated (aliphatic) alcohols bearing diverse functional groups.
- Powell, Adam B.,Stahl, Shannon S.
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supporting information
p. 5072 - 5075
(2013/10/22)
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- Transition metal-free direct C-H bond thiolation of 1,3,4-oxadiazoles and related heteroarenes
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A convenient transition metal-free procedure for the direct thiolation of 1,3,4-oxadiazole C-H bonds using diaryl disulfides has been developed. Other substrates including indole, benzothiazole, N-phenylbenzimidazole, and caffeine were also thiolated in this manner, providing the corresponding products in good to excellent yields. This journal is
- Zou, Liang-Hua,Reball, Jens,Mottweiler, Jakob,Bolm, Carsten
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supporting information
p. 11307 - 11309,3
(2020/10/15)
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- Facilitated photochemical cleavage of benzylic C-O bond. Application to photolabile hydroxyl-protecting group design
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A new photolabile hydroxyl-protecting group has been developed by introducing a dimethylamino group to the meta position of an aromatic ring of the traditional trityl (Tr) protecting group. The Royal Society of Chemistry 2010.
- Wang, Pengfei,Zhou, Lei,Zhang, Xin,Liang, Xing
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supporting information; experimental part
p. 1514 - 1516
(2010/06/12)
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- THIAZOLE AND OXAZOLE KINASE INHIBITORS
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The present invention provides thiazole and oxazole compounds, compositions containing the same, as well as processes for the preparation and methods for their use as pharmaceutical agents.
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Page/Page column 163
(2009/04/25)
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- Antileishmanial activity screening of 5-nitro-2-heterocyclic benzylidene hydrazides
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A series of 53 nitro derivatives rationally designed were obtained by parallel synthesis and screened against Leishmania donovani. Six compounds exhibited IC50 values lower than standard drugs. Brief SAR analysis revealed that substitution is important to the activity. Nitrothiophene analogues were more potent than the nitrofuran ones. This was attributed to the ability of sulfur atoms in accommodating electrons from nitro group, which facilitate its reduction and therefore the formation of free radicals lethal to parasites.
- Rando, Daniela G.,Avery, Mitchell A.,Tekwani, Babu L.,Khan, Shabana I.,Ferreira, Elizabeth I.
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p. 6724 - 6731
(2008/12/22)
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- Preparation of E-(2-substituted-1-methylethylidene)indanones derived from monic acid
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Alkylation of the lithium dienolate of the monic acid hydroxamate (3) with o-bromo(bromomethyl) benzene or heteroaromatic derivatives gave α-alkylated products (5). This alkylation procedure was surprisingly catalysed by 4- dimethylaminopyridine. Metal-halogen exchange with t-butyl lithium occurred with concomitant intramolecular cyclisation to give a mixture of the deconjugated ketones (6). Reconjugation with potassium t-butoxide stereoselectively produced the E-isomer (7). Deprotection gave the monic acid derived ketone (1).
- Pearson, Neil D.,Broom, Nigel J.P.,O'Hanlon, Peter J.
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p. 3771 - 3774
(2007/10/02)
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- Imidazopyridazines. V. Syntheses and Central Nervous Activities of Some 3-Alkoxy-6-benzylthio(substituted benzylthio and other phenylalkylthio)-2-phenyl(and substituted phenyl)imidazopyridazines
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Syntheses are reported for a number of 3-alkoxy-6-benzylthio(substituted benzylthio and other phenylalkylthio)-2-phenyl(and substituted phenyl)imidazopyridazines.These compounds were then examined for their ability to displace 3H-diazepam from rat
- Barlin, Gordon B.,Davies, Les P.,Ireland, Stephen J.,Ngu, Maria M. L.
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p. 1133 - 1146
(2007/10/02)
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- Syntheses of Highly Substituted Benzenes via Diels-Alder Reactions with 2H-Pyran-2-ones
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The 2H-pyran-2-ones (α-pyrones) 1 react as dienes in Diels-Alder reactions with acetylene derivatives.The primarely formed cycloadducts immediately aromatize to benzenes by CO2 elimination.Thus, methyl acetylenedicarboxylate (2a) gives dimethyl phthalates 3, and methyl acetylenediphosphonate (2b) gives dimethyl 1,2-phenylenediphosphonates 8.The reactions of 1-(dimethylamino)-1-methoxyethene (9) with 1 regioselectively produce N,N-dimethylanilines 10 and isomeric homophthalate derivatives 12.Naphthoquinones 14 could be generated from 1,4-benzoquinone (13) and 1 in the presence of acetic anhydride and Pd/C.Hydroxy-2H-pyran-2-ones 4 react via their trimethylsilyl ether 6 analogously with 2a to give dimethyl (trimethylsiloxy)phthalates 7 which are easily converted to phenols 5 by acid-catalyzed hydrolysis.
- Ziegler, Thomas,Layh, Marcus,Effenberger, Franz
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p. 1347 - 1356
(2007/10/02)
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