- Improved dimethylsulfoxonium methylide cyclopropanation procedures, including a tandem oxidation variant
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A new procedure for the cyclopropanation of α,β-unsaturated carbonyl compounds and related systems is described which employs trimethylsulfoxonium iodide and an organic base in acetonitile to generate dimethylsulfoxonium methylide in situ; in addition, pr
- Paxton, Richard J.,Taylor, Richard J. K.
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- Bioinspired Radical-Mediated Transition-Metal-Free Synthesis of N-Heterocycles under Visible Light
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A redox-active iminoquinone motif connected with π-delocalized pyrene core has been reported that can perform efficient two-electron oxidation of a class of substrates. The design of the molecule was inspired by the organic redox cofactor topaquinone (TPQ), which executes amine oxidation in the enzyme, copper amine oxidase. Easy oxidation of both primary and secondary alcohols happened in the presence of catalytic KOtBu, which could reduce the ligand backbone to its iminosemiquinonate form under photoinduced conditions. Moreover, this easy oxidation of alcohols under aerobic condition could be elegantly extended to multi-component, one-pot coupling for the synthesis of quinoline and pyrimidine. This organocatalytic approach is very mild (70 °C, 8 h) compared to a multitude of transition-metal catalysts that have been used to prepare these heterocycles. A detailed mechanistic study proves the intermediacy of the iminosemiquinonate-type radical and a critical hydrogen atom transfer step to be involved in the dehydrogenation reaction.
- K. Bains, Amreen,Ankit, Yadav,Adhikari, Debashis
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- Direct α-Acylation of Alkenes via N-Heterocyclic Carbene, Sulfinate, and Photoredox Cooperative Triple Catalysis
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N-Heterocyclic carbene (NHC) catalysis has emerged as a versatile tool in modern synthetic chemistry. Further increasing the complexity, several processes have been introduced that proceed via dual catalysis, where the NHC organocatalyst operates in concert with a second catalytic moiety, significantly enlarging the reaction scope. In biological transformations, multiple catalysis is generally used to access complex natural products. Guided by that strategy, triple catalysis has been studied recently, where three different catalytic modes are merged in a single process. In this Communication, direct α-C-H acylation of various alkenes with aroyl fluorides using NHC, sulfinate, and photoredox cooperative triple catalysis is reported. The method allows the preparation of α-substituted vinyl ketones in moderate to high yields with excellent functional group tolerance. Mechanistic studies reveal that these cascades proceed through a sequential radical addition/coupling/elimination process. In contrast to known triple catalysis processes that operate via two sets of interwoven catalysis cycles, in the introduced process, all three cycles are interwoven.
- Liu, Kun,Studer, Armido
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supporting information
p. 4903 - 4909
(2021/05/04)
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- Base-Mediated Site-Selective Hydroamination of Alkenes
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We present a base-mediated hydroamination protocol, using substoichiometric amounts of a hydrosilane and potassium tertbutoxide, that operates under mild conditions at 30 °C. Many aryl- and heteroatom-substituted olefins as well as arylamines are tolerated, affording the desired products with complete regioselectivity. Preliminary mechanistic investigations reveal a non-radical pathway for hydroamination. A sequential remote hydroamination strategy involving an initial Fe-catalysed olefin isomerisation followed by our base-mediated hydroamination was also developed to directly access-arylamines from terminal aliphatic alkenes.
- Koh, Ming Joo,Lee, Boon Chong,Li, Ping,Zhang, Xiaoxiang
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supporting information
(2021/12/29)
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- Direct 1,2-Dicarbonylation of Alkenes towards 1,4-Diketones via Photocatalysis
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1,4-Dicarbonyl compounds are intriguing motifs and versatile precursors in numerous pharmaceutical molecules and bioactive natural compounds. Direct incorporation of two carbonyl groups into a double bond at both ends is straightforward, but also challenging. Represented herein is the first example of 1,2-dicarbonylation of alkenes by photocatalysis. Key to success is that N(n-Bu)4+ not only associates with the alkyl anion to avoid protonation, but also activates the α-keto acid to undergo electrophilic addition. The α-keto acid is employed both for acyl generation and electrophilic addition. By tuning the reductive and electrophilic ability of the acyl precursor, unsymmetric 1,4-dicarbonylation is achieved for the first time. This metal-free, redox-neutral and regioselective 1,2-dicarbonylation of alkenes is executed by a photocatalyst for versatile substrates under extremely mild conditions and shows great potential in biomolecular and drug molecular derivatization.
- Chen, Bin,Cheng, Yuan-Yuan,Hou, Hong-Yu,Lei, Tao,Tung, Chen-Ho,Wu, Li-Zhu,Yu, Ji-Xin
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supporting information
p. 26822 - 26828
(2021/11/17)
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- Visible-light-induced triple catalysis for a ring-opening cyanation of cyclopropyl ketones
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An unprecedented triple catalytic, general ring-opening cyanation reaction of cyclopropyl ketones for the construction of γ-cyanoketones is described. The key is to merge photoredox catalysis with Lewis acid catalysis and copper catalysis to enable the selective cleavage of the carbon-carbon bonds and the selective coupling of the generated radical and cyanide anion.
- Liu, Jing,Liu, Xiao-Peng,Wu, Hong,Wei, Yi,Lu, Fu-Dong,Guo, Kai-Rui,Cheng, Ying,Xiao, Wen-Jing
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supporting information
p. 11508 - 11511
(2020/10/12)
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- Nickel-catalysed chemoselective C-3 alkylation of indoles with alcohols through a borrowing hydrogen method
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An inexpensive, air-stable, isolable nickel catalyst is reported that can perform chemoselective C3-alkylation of indoles with a variety of alcohols following "borrowing hydrogen". A one-pot, cascade C3-alkylation starting from 2-aminophenyl ethyl alcohols, and thus obviating the need for pre-synthesized indoles, further adds to the broad scope of this method. The reaction is radical-mediated, and is significantly different from other examples, often dictated by metal-ligand bifunctionality. This journal is
- Adhikari, Debashis,Bains, Amreen K.,Biswas, Ayanangshu
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supporting information
p. 15442 - 15445
(2020/12/25)
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- Iron-Catalyzed Radical Acyl-Azidation of Alkenes with Aldehydes: Synthesis of Unsymmetrical β-Azido Ketones
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An iron-catalyzed acyl-azidation of alkenes under mild reaction conditions has been developed. Aromatic aldehydes or aliphatic aldehydes can be used as the acyl radical precursors; TMSN3 is used as the azido source; TBHP is the initiator. The s
- Ge, Liang,Li, Yajun,Bao, Hongli
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supporting information
p. 256 - 260
(2019/01/10)
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- Electrogenerated Sm(II)-Catalyzed CO2 Activation for Carboxylation of Benzyl Halides
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Sm(II)-catalyzed carboxylation of benzyl halides is reported through the electrochemical reduction of CO2. The transformation proceeds under mild reaction conditions to afford the corresponding phenylacetic acids in good to excellent yields. This user-friendly and operationally simple protocol represents an alternative to traditional strategies, which usually proceeds through the C(sp3)-halide activation pathway.
- Bazzi, Sakna,Schulz, Emmanuelle,Mellah, Mohamed
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supporting information
p. 10033 - 10037
(2019/12/24)
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- Regiospecific Intermolecular Aminohydroxylation of Olefins by Photoredox Catalysis
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A simple and regiospecific aminohydroxylation of olefins by photoredox catalysis has been developed. N-protected 1-aminopyridinium salts are the key compounds and serve as amidyl radical precursors by the action of Ir photocatalysts, fac-[Ir(ppy)3/s
- Miyazawa, Kazuki,Koike, Takashi,Akita, Munetaka
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supporting information
p. 11677 - 11680
(2015/08/11)
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- Palladium-catalyzed cross-coupling of styrenes with aryl methyl ketones in ionic liquids: Direct access to cyclopropanes
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The combined use of Pd(OAc)2, Cu(OAc)2, and dioxygen in molten tetrabutylammonium acetate (TBAA) promotes an unusual cyclopropanation reaction between aryl methyl ketones and styrenes. The process is a dehydrogenative cyclizing coupl
- Cotugno, Pietro,Monopoli, Antonio,Ciminale, Francesco,Milella, Antonella,Nacci, Angelo
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supporting information
p. 13563 - 13567
(2015/01/09)
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- Aerobic oxidation of secondary benzylic alcohols and direct oxidative amidation of aryl aldehydes promoted by sodium hydride
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We reported herein new reactivities and possible mechanistic implications of a simplest oxidant (NaH/air) uncovered on a broad range of useful transformations, including aerobic alcohol oxidations, allylic alcohol isomerizations and oxidations, cyclopropyl alcohol fragmentations, and direct aryl aldehyde oxidative amidations. These readily implementable transition-metal-free processes feature exceptional material accessibility, operational simplicity, and environmental compatibility, and add new dimensions to its synthetic utilities that are fairly robust yet had not previously been fully realized and systematically explored.
- Wang, Xinbo,Wang, David Zhigang
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supporting information; experimental part
p. 3406 - 3411
(2011/06/17)
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- Indium triflate catalyzed rearrangement of aryl-substituted cyclopropyl carbinols to 1,4-disubstituted 1,3-butadienes
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Aryl-substituted cyclopropyl carbinol derivatives undergo a facile stereoselective rearrangement catalyzed by In(OTf)3 in dichloromethane under sonication to produce the substituted conjugated all-trans-butadienes. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Ranu, Brindaban C.,Banerjee, Subhash
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p. 3012 - 3015
(2007/10/03)
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- Chemoselective Nucleophilic Attack on N-Acyl Derivatives of (S)-Ethyl 4,4-Dimethyl Pyroglutamate (DMPG)
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(Matrix presented) Heteronucleophiles and C-nucleophiles chemoselectively react with N-acyl (S)-ethyl 4,4-dimethyl pyroglutamate (DMPG) affording esters, amides, and ketones in high yield. The intramolecular process allows the stereoselective formation of β-hydroxy acids likely by formation and ring opening of the corresponding β-lactones.
- Mantecon, Susana,Vaquero, Juan J.,Alvarez-Builla, Julio,De La Puente, Maria Luz,Espinosa, Juan F.,Ezquerra, Jesus
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p. 3791 - 3794
(2007/10/03)
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- Chemoselective C-H oxidation of alcohols to carbonyl compounds with iodosobenzene catalyzed by (Salen)chromium complex
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Primary and secondary alcohols with benzylically and allylically activated C-H bonds are chemoselectively oxidized to the corresponding carbonyl compounds by the (salen)Cr(III) complex I as the catalyst and iodosobenzene as the oxygen source; the oxidizing species is the Cr(V) oxo complex. Allylic alcohols with fully substituted double bonds give appreciable amounts of epoxides besides the C-H oxidation products enones, while saturated alcohols are less readily oxidized.
- Adam, Waldemar,Gelalcha, Feyissa Gadissa,Saha-Moeller, Chantu R.,Stegmann, Veit R.
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p. 1915 - 1918
(2007/10/03)
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- S-Ethenylsulfoximine Derivatives. Reagents for Ethylenation of Protic Nucleophiles
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The preparation of S-vinyl and S-(2-substituted)ethenyl derivatives of sulfoximines is described.Vinyl-, (2-phenylethenyl)-, (2,2-diphenylethenyl)-, (2-methyl-1-propenyl)-, (dimethylamino)phenyloxosulfonium fluoroborates were found to undergo an addition-elimination reaction sequence with protic nitrogen and carbon nucleophiles, resulting in ethylenation of the nucleophile and N,N-dimethylbenzenesulfinamide.Primary amines gave aziridines, enamines gave cyclopropyl derivatives of iminium salts or pyrrolidinium salts, anions of active methylene compounds gave dihydrofurans and/or cyclopropanes, and anions of nitroalkanes gave cyclic nitronic esters and/or nitrocyclopropanes.In several cases vinyl salts were generated in situ from β-methoxyoxosulfonium salts.Treatment of (-)-(S)-dimethylamino)phenyl(trans-2-phenylethenyl)oxosulfonium fluoroborate with methyl cyanoacetate in methanol containing sodium methoxide gave, in 81percent yield, (+)-(1S,2R)-methyl 1-cyano-2-phenylcyclopropanecarboxylate of 25.5percent optical purity.The same salt upon treatment with methyl nitroacetate gave, in 95percent yield, methyl 4-phenyl-3-isoxazolinecarboxylate 2-oxide with 33percent enantiomeric excess.Cyclopropanes were formed upon treatment of S-methyl-S-(trans-2-phenylethenyl)-N-(p-tolylsulfonyl)sulfoximine with anions of active methylene compounds.
- Johnson, Carl R.,Lockard, James P.,Kennedy, Eugene R.
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p. 264 - 271
(2007/10/02)
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