- Enhanced structural variety of nonplanar N-oxyl radical catalysts and their application to the aerobic oxidation of benzylic C-H bonds
-
The design and synthesis of structurally variable, nonplanar N-oxyl radical catalysts and their application to the aerobic oxidation, etherification, and acetoamidation of benzylic C-H bonds are described. The catalytic oxidation of C-H bonds represents a powerful tool to synthesize oxygenated functional molecules from simple hydrocarbons in a straightforward way. Electron-deficient N-oxyl radical catalysts, such as phthalimidoyl N-oxyl (PINO) radical, generated from N-hydroxyphthalimide (1), have attracted much attention because of their applications in the oxidation of C-H bonds with high bond dissociation energy (BDE). However, a few sites in 1 are available for structural modifications and improvements of the catalytic performance. By replacing one carbonyl group in 1 with a trifluoromethyl (CF3)-substituted sp3-carbon, we generated an additional tunable site and a nonplanar backbone, while retaining the desirable electron-withdrawing properties and increasing the lipophilicity with respect to 1. We synthesized a variety of N-hydroxy pre catalysts containing such a CF3 moiety, and investigated their utility in the aerobic oxidation of benzylic C-H bonds. Precatalysts with electron-withdrawing substituents, such as trifluoroethoxy and the acetophenone moieties, afforded higher yields than a corresponding methoxy-substituted analogue. The introduction of substituents at the aromatic ring was also effective, as evident from the performance of 7-CF3 and 4,5,6,7-tetrafluoro precatalysts. Especially the combination of trifluoroethoxy- and 4,5,6,7-tetrafluoro substitution afforded a superior performance. These catalyst systems exhibited high functional group tolerance during the aerobic oxidation of C-H bonds, and benzylic etherification and Ritter-type reactions could be carried out at room temperature when a selected precatalyst and N-bromosuccinimide (NBS) were used.
- Kadoh, Yoichi,Oisaki, Kounosuke,Kanai, Motomu
-
-
Read Online
- Cobalt-Catalyzed Aerobic Oxidative Cleavage of Alkyl Aldehydes: Synthesis of Ketones, Esters, Amides, and α-Ketoamides
-
A widely applicable approach was developed to synthesize ketones, esters, amides via the oxidative C?C bond cleavage of readily available alkyl aldehydes. Green and abundant molecular oxygen (O2) was used as the oxidant, and base metals (cobalt and copper) were used as the catalysts. This strategy can be extended to the one-pot synthesis of ketones from primary alcohols and α-ketoamides from aldehydes.
- Li, Tingting,Hammond, Gerald B.,Xu, Bo
-
p. 9737 - 9741
(2021/05/31)
-
- Visible-light-promoted site-specific and diverse functionalization of a c(sp3)-c(sp3) bond adjacent to an arene
-
We report here a strategy for inert C-C bond functionalization. Site-specific cleavage and functionalization of a saturated C(sp3)-C(sp3) bond via a visible-light-induced radical process have been achieved. The general features of this reaction are as follows. (1) Both linear and cyclic C(sp3)-C(sp3) bonds with a vicinal arene can be specifically functionalized. (2) One carbon is converted into a ketone, and another can be tunably converted into nitrile, peroxide, or halide. (3) The typical conditions include 1.0 mol % of Ru(bpy)3Cl2, 1.0 or 5.0 equiv of Zhdankin reagent, white CFL (24 W), open flask, and room temperature. These reactions offer powerful tools to modify carbon skeletons that are intractable by conventional methods. Good selectivity and functional group tolerance, together with mild and open air conditions, make these transformations valuable and attractive.
- Fang, Fang,Liu, Zhong-Quan,Sun, Minzhi,Wang, Nengyong,Wang, Yaxin,You, Huichao,Zhao, Jianyou
-
p. 6603 - 6612
(2020/07/27)
-
- Syntheses of Pyrroles, Pyridines, and Ketonitriles via Catalytic Carbopalladation of Dinitriles
-
The first example of the Pd-catalyzed addition of organoboron reagents to dinitriles, as an efficient means of preparing 2,5-diarylpyrroles and 2,6-diarylpyridines, has been discussed here. Furthermore, the highly selective carbopalladation of dinitriles with organoboron reagents to give long-chain ketonitriles has been developed as well. Based on the broad scope of substrates, excellent functional group tolerance, and use of commercially available substrates, the Pd-catalyzed addition reaction of arylboronic acid and dinitriles is expected to be significant in future synthetic procedures.
- Qi, Linjun,Li, Renhao,Yao, Xinrong,Zhen, Qianqian,Ye, Pengqing,Shao, Yinlin,Chen, Jiuxi
-
supporting information
p. 1097 - 1108
(2020/01/22)
-
- Palladium-Catalyzed Cascade Reactions of I-Ketonitriles with Arylboronic Acids: Synthesis of Pyridines
-
This study presents the first example of the Pd-catalyzed cascade reactions of 5-oxohexanenitrile with arylboronic acids, affording important synthon 2-methylpyridines that can be further translated through C(sp3)-H functionalization to construct pyridine derivatives. Furthermore, this chemistry allows 5-oxo-5-Arylpentanenitrile to react with arylboronic acids to provide unsymmetrical 2,6-diarylpyridines. This protocol paves the way for the practical and atom economical syntheses of valuable pyridines with broad functional groups in moderate to excellent yields under mild conditions.
- Chen, Jiuxi,Hu, Maolin,Li, Renhao,Liu, Jichao,Qi, Linjun,Shao, Yinlin,Yao, Xinrong,Zhao, Zhiwei,Zhen, Qianqian
-
supporting information
p. 114 - 119
(2020/03/25)
-
- Nickel-Catalyzed Reductive Electrophilic Ring Opening of Cycloketone Oxime Esters with Aroyl Chlorides
-
By merging cross-electrophile coupling and C-C bond cleavage, we developed a Ni-catalyzed electrophilic ring opening of cycloketone oxime esters with aromatic acid chlorides in assistance of Mn as reductant. Notably, complete regioselectivity can be achieved in this C-C bond cleavage reaction, providing an efficient access to a variety of cyanoketones under cyanide-free conditions. A radical reaction pathway was proposed on the basis of the results of the mechanistic probing experiments.
- Ding, Decai,Wang, Chuan
-
p. 11324 - 11329
(2019/01/03)
-
- Photoinduced C—C Bond Cleavage and Oxidation of Cycloketoxime Esters
-
A novel structural reorganization of cycloketoxime esters beyond the traditional Beckmann rearrangement process has been established to build cyano-containing ketones in the presence of photocatalyst. This novel transformation is remarkable with selective C—C bond cleavage and an oxidation process enabled by DMSO used as the solvent, oxidant, and oxygen source avoiding acid, base and toxic cyanide salts as the cyano source. Further applications in late-stage modification of complex and chiral molecules have also been reported.
- Zhao, Binlin,Tan, Hui,Chen, Cheng,Jiao, Ning,Shi, Zhuangzhi
-
p. 995 - 999
(2018/09/25)
-
- C-C Bond-Forming Strategy by Manganese-Catalyzed Oxidative Ring-Opening Cyanation and Ethynylation of Cyclobutanol Derivatives
-
A novel C-C bond-forming strategy employing manganese-catalyzed ring-opening of cyclobutanol substrates, followed by cyanation or ethynylation, is described. A cyano C1 unit and ethynyl C2 unit are regiospecifically introduced to the γ-position of ketones at room temperature, providing a mild yet powerful method for production of elusive aliphatic nitriles and alkynes. All transformations described are based on a common sequence: 1) oxidative ring-opening of cyclobutanol substrates by C-C bond cleavage; 2) radical addition to triple bonds bearing an arylsulfonyl group; and 3) radical-mediated C-S bond cleavage.
- Ren, Rongguo,Wu, Zhen,Xu, Yan,Zhu, Chen
-
supporting information
p. 2866 - 2869
(2016/02/27)
-
- Enantioselective titanium(III)-catalyzed reductive cyclization of ketonitriles
-
Reduction, please! The title reaction affords ?-hydroxyketones, a common structural motif in biologically active natural products, in good yields and high enantioselectivities at room temperature. The commercially available ansa-titanocene 1 was found to be an efficient catalyst for this process, which presumably proceeds by addition of a ketyl radical to a nitrile.
- Streuff, Jan,Feurer, Markus,Bichovski, Plamen,Frey, Georg,Gellrich, Urs
-
p. 8661 - 8664
(2012/09/21)
-
- Direct and selective benzylic oxidation of alkylarenes via C-H abstraction using alkali metal bromides
-
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
-
supporting information; experimental part
p. 2414 - 2417
(2012/06/18)
-
- Unified oxidation protocol for the synthesis of carbonyl compounds using a manganese catalyst
-
We have developed a unified protocol for the oxidation of ethers, benzylic compounds, and alcohols to carbonyl compounds. The protocol uses catalytic amounts of manganese(II) chloride tetrahydrate and tri(t-butyl)-2,2':6',2Prime;- terpyridine in combination with a stoichiometric amount of either m-chloroperbenzoic acid (MCPBA) or potassium hydrogen peroxysulfate (KHSO 5). A reagent system consisting of the Mn catalyst and MCPBA permitted the chemoselective sp3 C-H oxidation of alkyl ethers and benzylic compounds to generate the corresponding ketones. Alternatively, the water-soluble inorganic salt KHSO5 in combination with the Mn catalyst was used to oxidize alcohols to ketones or carboxylic acids. Importantly, the Mn catalyst/KHSO5 system eliminates technical difficulties associated with the isolation of carboxylic acid products. All the oxidations presented in this feature article proceed at sup-ambient temperature in an aerobic atmosphere, and can therefore be used in practical syntheses of complex organic molecules. Georg Thieme Verlag Stuttgart · New York.
- Kamijo, Shin,Amaoka, Yuuki,Inoue, Masayuki
-
experimental part
p. 2475 - 2489
(2010/09/06)
-
- Photochemical synthesis of highly functionalized cyclopropyl ketones
-
A series of di- and trisubstituted cyclopropyl ketones 11 were prepared by irradiation of ketones 3 and 5, which bear a leaving group adjacent to the carbonyl C-atom. The required ketones 3 could be easily synthesized either by functionalization of ketones 1 with a hypervalent iodine reagent, 2, or by O-sulfonylation of α-hydroxy ketones 7. The nitrates 5 were obtained by treatment of the corresponding α-bromo ketones with AgNO3. The irradiation of 3 and 5 must be performed in the presence of an acid scavenger (1-methyl-1H-imidazole) to obtain the cyclopropanes 11 in good yields. The synthetic efficiency of the method was, among other things, demonstrated by the preparation of a highly strained bicyclo[2.1.0]pentane 11i in good yield. The mechanism of the photochemical cyclization was investigated by means of photokinetic measurements, as well as by quantum-chemical calculations. It was shown that the presence of the leaving group substantially influences all steps of the photochemical reaction cascade. The X-ray crystal structures of 11j and exo-11k were also determined.
- Wessig, Pablo,Muehling, Olaf
-
p. 865 - 893
(2007/10/03)
-
- Oxidative fragmentation of 1-aryl-1-cycloalkenes using cerium(IV) ammonium nitrate (CAN): Some novel observations
-
1-Phenyl-1-cycloalkenes undergo oxidative fragmentation in presence of CAN in methanol, affording 1,n-dicarbonyl compounds as the major products along with 1,2-dimethoxycycloalkanes. The reaction under deoxygenated conditions afforded the latter in good yields. In the presence of azide ion, fragmentation leading to the corresponding cyanoketones was observed whereas with sulfinate only the 1-methoxy-2-sulfonyl cycloalkanes were formed.
- Nair, Vijay,Panicker, Sreeletha B,Thomas, Siji,Santhi,Mathai, Sindhu
-
p. 3229 - 3234
(2007/10/03)
-
- Substituted tetrahydrofuroyl-1-phenylalanine derivatives as potent and specific VLA-4 antagonists
-
A series of substituted tetrahydrofuroyl-1-phenylalanine derivatives was prepared and evaluated as VLA-4 antagonists. Substitution of the α carbon of the tetrahydrofuran with aryl groups increased the specificity for VLA-4 versus α4β7 while amide substitution increased the potency of the series without increasing the specificity. Substitution of the β carbon of the tetrahydrofuran with keto or amino groups slightly improved the specificity for VLA-4 versus α4β7 but with a significant loss in binding affinity for VLA-4.
- Doherty, George A.,Yang, Ginger X.,Borges, Edite,Chang, Linda L.,MacCoss, Malcolm,Tong, Sharon,Kidambi, Usha,Egger, Linda A.,McCauley, Ermenegilda,Van Riper, Gail,Mumford, Richard A.,Schmidt, John A.,Hagmann, William K.
-
p. 1501 - 1505
(2007/10/03)
-
- Debenzotriazolylation of α-benzotriazolyl ketones with samarium diiodide
-
Removal of the benzotriazolyl moiety of α-benzotriazolyl ketones by samarium diiodide at room temperature to give the corresponding ketones in good yields is described.
- Katritzky, Alan R.,Wang, Junquan,Henderson, Scott A.
-
p. 1567 - 1574
(2007/10/03)
-
- Preparation and Chemistry of the Active Copper Species Derived from CuI*PBu3, CuI*PPh3, and CuCN*nLiX Complexes
-
The preparation of highly reactive copper by the reduction of CuI*PBu3, CuI*PPh3, and CuCN*nLiX copper(I) complexes with the preformed lithium naphthalenide is described.It was found, for all three Cu(I) complexes, that the reduction temperature proved crucial to reactivity of the zerovalent copper species as measured by the ability of the active copper to undergo oxidative addition to carbon-halogen bonds.The lower the reduction temperature the more reactive the zerovalent copper species becomes.The low-temperature reduction allows for the formation of highly reactive copper from CuCN*nLiX complexes.This active copper species undergoes oxidative addition to alkyl and aryl bromides in high yield to form the corresponding organocopper reagent directly without the need for other organometallic precursors.Moreover, the alkyl and aryl bromides can obtain a wide range of functional groups as they are not affected in the oxidative addition step.The functionalized organocopper reagents derived from CuCN*nLiX based active copper are the reagent of choice in the cross-coupling of acid chlorides to produce ketones as well as the 1,4-addition reaction with enones.The lack of phosphines associated with organocopper reagents stemming from CuCN-based active copper makes product isolation more facile.While the functionalized organocopper reagents derived from CuCN*nLiX complexes provide higher isolated yields in the formentioned reactions, they are not nucleophilic enough to undergo inter- or intramolecular epoxide openings.The use of both CuI*PBu3 and CuI*PPh3 Cu(I) complexes in the intramolecular epoxide openings of aryl bromoepoxides is presented.The regiochemistry, endo vs. exo, was shown to be affected by the Cu(I) complex used to generate the active copper species, the solvent, and the pattern of substitution around the epoxide moiety.The active copper species as well as the resulting organocopper reagents derived from both CuI*PBu3 and CuCN*nLiX were investigated using both 31P and 13C NMR.The data from 31P NMR investigation held some evidence for a highly reduced copper(0)-phosphine complex while the 13C studies of the CuCN*nLiX complexes indicated that these species have limited solubility in THF.
- Rieke, Reuben D.,Stack, Douglas E.,Dawson, Bryan T.,Wu, Tse-Chong
-
p. 2483 - 2491
(2007/10/02)
-
- Direct Formation and Reaction of Thienyl-Based Organocopper Reagents
-
The preparation of a highly reactive zerovalent copper complex by the direct reduction of lithium (2-thienylcyano)cuprate with preformed lithium naphthalenide is described.This active copper species oxidatively adds to carbon-halogen bonds to form organocopper reagents.The ability to directly form the organocopper reagent from organic halides and active copper allows for the incorporation of a wide variety of functionalities to be present in the organic halides and the organocopper reagents.Significantly, this formulation of active copper was able to oxidatively add to allyl chlorides and acetates at low temperatures to allow the direct formation of allylic organocopper reagents without Wurtz-type homocoupling.These functionalized organocopper compounds are able to undergo a variety of reactions, such as cross-coupling with acid chlorides, 1,4-conjugate addition with α,β-unsaturated carbonyl compounds, and intermolecular and intramolecular epoxide-opening reactions.Subsequently, this copper species avoids the use of phosphine ligands affording the product isolation much more convenient than with phosphine-based organocopper reagents.
- Rieke, Reuben D.,Klein, Walter R.,Wu, Tse-Chong
-
p. 2492 - 2500
(2007/10/02)
-
- NEW ORGANOCOPPER REAGENTS PREPARED UTILIZING HIGHLY REACTIVE COPPER
-
Highly reactive copper solutions have been prepared by the lithium naphthalide reduction of copper(I) iodide/trialkylphosphine complexes.These activated copper solutions will react with organic halides under very mild conditions to form stable organocopper reagents.Significantly, the organocopper reagents can contain considerable functionalities such as ester, nitrile, chloride, epoxide, and ketone groups.These functionalized organocopper species undergo many reactions typical of other organocopper species.Intermolecular 1,4-additions, epoxide-opening reactions, and ketone formation with acid chlorides have been successfully achieved.In addition, this methodology has been applied to an intramolecular epoxide-cleavage reaction.The influence of the connecting chain length, substitution pattern, reaction solvent, and CuI/phosphine complex upon the regioselectivity of the intramolecular cyclization is described.
- Rieke, Reuben D.,Wehmeyer, Richard M.,Wu, Tse-Chong,Ebert, Greg W.
-
p. 443 - 454
(2007/10/02)
-
- DIRECT FORMATION AND REACTION OF FUNCTIONALIZED THIENYL-BASED ORGANOCOPPER REAGENTS
-
Highly reactive copper solutions have been prepared by the direct reduction of lithium 2-thienylcyanocuprate.Product isolation was much easier using the thienyl-based organocopper reagents as opposed to phosphine-based organocopper reagents
- Rieke, Reuben D.,Wu, Tse-Chong,Stinn, Dean E.,Wehmeyer, Richard M.
-
p. 1833 - 1840
(2007/10/02)
-
- DIRECT FORMATION OF FUNCTIONALIZED KETONES VIA THE COUPLING OF FUNCTIONALIZED ORGANOCOPPER REAGENTS WITH ACID CHLORIDES
-
Highly reactive copper solutions have been prepared by the lithium naphtalide reduction of copper(I) iodide/triphenyl-phosphine complex.These copper solutions react rapidly with functionalized alkyl halides to give organocopper reagents wich have been effectively trapped with acid chlorides giving functionalized ketones in good yields.Ester, nitrile, chloride, remote epoxide, and, to some degree, ketone groups can be tolerated by this approach.
- Wehmeyer, Richard M.,Rieke, Reuben D
-
p. 4513 - 4516
(2007/10/02)
-
- Synthesis and Reactivity toward Acyl Chlorides and Enones of the New Highly Functionalized Copper Reagents RCu(CN)ZnI
-
The new and highly functionalized copper reagents RCu(CN)ZnI obtained from readily available primary and secondary alkylzinc iodides by a transmetalation in THF with the soluble salt, CuCN*2LiX, react in good yields with acyl chlorides and enones, respectively, to afford ketones and 1,4-addition products.
- Knochel, Paul,Yeh, Ming Chang P.,Berk, Scott C.,Talbert Jason
-
p. 2390 - 2392
(2007/10/02)
-
- Synthesis of Nitriles from Haloesters, Haloketones and Haloethers
-
The action of NaCN on haloesters, haloketones and haloethers has been studied.Haloesters wherein halogen and ester functions are located on adjacent carbon atoms, do not furnish the corresponding nitriles, whereas those with halogen and ester functions not located on adjacent carbon atoms, furnish the corresponding nitriles in good yields.The presence of hydroxy or ether function on the carbon adjacent to primary halide bearing carbon atom does not interfere in the reaction with cyanide. δ-Haloketones are transformed to ketonitriles, γ-Haloketones are transformed to cyclopropyl ketones and epoxyhalides to epoxynitriles.
- Talekar, D. G.,Joshi, P. L.,Ramaiah, P.,Rao, A. S.
-
p. 145 - 151
(2007/10/02)
-
- Acid Decomposition of 5-Amino-1-vinyl-4,5-dihydro-1H-1,2,3-triazoles. A Novel Formation of 1-Amino-2-azabutadienes
-
Acid decomposition of 4-alkyl-5-dialkyl-amino-1-vinyl-4,5-dihydro-1H-1,2,3-triazoles gave N1,N1-dialkyl-N2-vinylalkanamidines, which have 2-aza-1,3-butadiene skeleton, in fair yields.
- Ito, Masato M.,Nomura, Yujiro,Takeuchi, Yoshito,Tomoda, Shuji
-
p. 641 - 642
(2007/10/02)
-