- Base-Catalyzed [3 + 2] Cycloaddition of N-Benzyl Ketimines to Arylacetylenes Followed by Oxidation: A One-Pot Access to Polyarylated 2 H-Pyrroles via Intermediate Pyrrolines
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N-Benzyl ketimines undergo [3 + 2] cycloaddition with arylacetylenes in the KOBut/DMSO solution to 2,3,5-triarylpyrrolines, which are oxidized (chloranil, DDQ) in situ to 2,3,5-triaryl-2H-pyrroles in 53-71% yields. The intermediate 1-pyrrolines can be isolated in 31-91% yields and separately oxidized to the corresponding 2H-pyrroles.
- Bidusenko, Ivan A.,Schmidt, Elena Yu.,Trofimov, Boris A.,Ushakov, Igor A.,Vashchenko, Alexander V.
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supporting information
p. 4121 - 4126
(2021/06/28)
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- Metal-free oxidative cross-coupling of diazirines with arylboronic acids
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We report herein a metal-free cross-coupling of diazirines with arylboronic acids under oxidative conditions. The reaction affords a series of substituted olefins. It is proposed that the interaction between the nitrogen on diazirine with arylboronic acid plays a key role in this transformation.
- Wu, Guojiao,Zhao, Xia,Ji, Wenzhi,Zhang, Yan,Wang, Jianbo
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supporting information
p. 1961 - 1963
(2016/02/05)
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- gem-Difluoroolefination of Diazo Compounds with TMSCF3 or TMSCF2Br: Transition-Metal-Free Cross-Coupling of Two Carbene Precursors
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A new olefination protocol for transition-metal-free cross-coupling of two carbene fragments arising from two different sources, namely, a nonfluorinated carbene fragment resulting from a diazo compound and a difluorocarbene fragment derived from Ruppert-Prakash reagent (TMSCF3) or TMSCF2Br, has been developed. This gem-difluoroolefination proceeds through the direct nucleophilic addition of diazo compounds to difluorocarbene followed by elimination of N2. Compared to previously reported Cu-catalyzed gem-difluoroolefination of diazo compounds with TMSCF3, which possesses a narrow substrate scope due to a demanding requirement on the reactivity of diazo compounds and in-situ-generated CuCF3, this transition-metal-free protocol affords a general and efficient approach to various disubstituted 1,1-difluoroalkenes, including difluoroacrylates, diaryldifluoroolefins, as well as arylalkyldifluoroolefins. In view of the ready availability of diazo compounds and difluorocarbene reagents and versatile transformations of 1,1-difluoroalkenes, this new gem-difluoroolefination method is expected to find wide applications in organic synthesis.
- Hu, Mingyou,Ni, Chuanfa,Li, Lingchun,Han, Yongxin,Hu, Jinbo
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supporting information
p. 14496 - 14501
(2015/11/27)
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- An (Aminopyrimidinato)titanium catalyst for the hydroamination of alkynes and alkenes
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A new (aminopyrimidinato)titanium complex has been synthesised from inexpensive and easily accessible 2-(tert-butylamino)pyrimidine and [Ti(NMe 2)4] and used as a catalyst for the intermolecular hydroamination of alkynes as well as the cyclization of aminoalkenes. The hydroamination reactions of 1-phenylpropyne and terminal arylalkynes deliver the corresponding anti-Markovnikov addition products with excellent yields and regioselectivities. A new (aminopyrimidinato)titanium complex has been synthesised from inexpensive 2-(tert-butylamino)pyrimidine and [Ti(NMe 2)4] and used as a catalyst for the intermolecular hydroamination of alkynes as well as the cyclization of aminoalkenes. The complex represents the first example of a catalyst for the hydroamination of alkynes that contains an aminoheteroaromatic ancillary ligand.
- Brahms, Christian,Tholen, Patrik,Saak, Wolfgang,Doye, Sven
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p. 7583 - 7592
(2013/12/04)
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- Asymmetric hydrogenation of N-alkyl and N-aryl ketimines using chiral cationic Ru(diamine) complexes as catalysts: The counteranion and solvent effects, and substrate scope
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Asymmetric hydrogenation of N-alkyl and N-aryl ketimines catalyzed by chiral cationic η6-arene-(N-monosulfonylated diamine) Ru(II) complexes has been investigated. Strong counteranion and solvent effects on the enantioselectivity were observed. The ruthenium catalyst bearing non-coordinating BArF- anion was found to be particularly effective for the hydrogenation of acyclic and exocyclic N-alkyl ketimines in the presence of (Boc)2O in dichloromethane or even under solvent-free conditions, providing chiral amines with up to >99% ee and full conversions. Alternatively, the ruthenium catalyst bearing achiral phosphate anion together with corresponding phosphoric acid as the additive was also efficient for the hydrogenation of N-alkyl ketimines in the absence of (Boc)2O with excellent enantioselectivities and full conversions. For N-aryl ketimines lower enantiomeric excesses were observed by using the ruthenium catalyst bearing BArF- anion. This catalytic protocol thus provides a facile and practical access to optically active amines and has been successfully employed in the gram-scale synthesis of enantiomerically pure (+)-sertraline.
- Chen, Fei,Ding, Ziyuan,He, Yanmei,Qin, Jie,Wang, Tianli,Fan, Qing-Hua
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supporting information; experimental part
p. 5248 - 5257
(2012/08/08)
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- Asymmetric hydrogenation of N-Alkyl ketimines with phosphine-free, chiral, cationic Ru-MsDPEN catalysts
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(Solvent) free and easy: A phosphine-free, chiral, cationic Ru-MsDPEN complex [(S,S)-1] is found to be an efficient catalyst for the enantioselective hydrogenation of a range of often-problematic N-alkyl ketimines (see scheme). This new method provides a more practical and greener synthetic approach to optically active amines, particularly N-alkyl amines, such as Sertraline.
- Chen, Fei,Wang, Tianli,He, Yanmei,Ding, Ziyuan,Li, Zhiwei,Xu, Lijin,Fan, Qing-Hua
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supporting information; experimental part
p. 1109 - 1113
(2011/03/21)
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- Microwave-assisted, Pd(0)-catalyzed cross-coupling of diazirines with aryl halides
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Pd(0)-catalyzed cross-coupling reactions of diazirines with aryl halides under microwave heating conditions afford a series of substituted olefins. A reaction mechanism involving the migratory insertion of the Pd carbene intermediate is proposed.
- Zhao, Xia,Wu, Guojiao,Yan, Chong,Lu, Kui,Li, Hui,Zhang, Yan,Wang, Jianbo
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supporting information; experimental part
p. 5580 - 5583
(2011/02/23)
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- Highly enantioselective construction of axial chirality by palladium-catalyzed cycloisomerization of N- alkenyl arylethynylamides
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A cationic palladium(ll)/(S)-xyl-Segphos complex catalyzes enantioselective cycloisomerizations of N-alkenyl arylethynylamldes leading to axlally chlral 4-aryl-2-pyridones In high yields with high ee values. The present catalysis represents the first enantioselective construction of axial chlrallty by the transition-metal-catalyzed cyclolsomerlzatlon.
- Lmase, Hidetomo,Suda, Takeshi,Shibata, Yu,Noguchi, Keiichi,Hirano, Masao,Tanaka, Ken
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supporting information; experimental part
p. 1805 - 1808
(2009/09/25)
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- A highly enantioselective organocatalytic method for reduction of aromatic N-alkyl ketimines
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A study has demonstrated the development of a highly enantioselective catalytic method for the reduction of aromatic N-alkyl ketimines by trichlorosilane under mild conditions using the newly designed Lewis base organocatalyst that incorporates C- and S-chirality. The S-chiral sulfinamide group in these catalysts plays a crucial role similar to the carboxamide groups as Lewis base for the activation of HSiCl3, and also serves as a source of chirality that the carboxamide group lacks for the asymmetric induction. The results of the study showed that excellent enantioselectivities of up to 99.6% ee and high yields were obtained for a wide range of substrates. Further works is also in progress to clarify the mechanism of the transformation and explore the full application scope of the present catalyst system.
- Wang, Chao,Wu, Xinjun,Zhou, Li,Sun, Jian
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supporting information; experimental part
p. 8789 - 8792
(2009/09/25)
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- A general study of aryloxo and alkoxo ligands in the titanium-catalyzed intermolecular hydroamination of terminal alkynes
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A general study of the regioselective hydroamination of terminal alkynes in the presence of Ti(NEt2)4 and different aryloxo and alkoxo ligands is presented. Depending on the ligand the regioselectivity towards the Markovnikov and the anti-Markovnikov addition product can be controlled. The experimentally observed isomer distribution is explained perfectly by detailed theoretical investigations which demonstrate that the regioselectivity is determined by the relative stability of the corresponding alkynetitanium π complexes. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Tillack, Annegret,Khedkar, Vivek,Jiao, Haijun,Beller, Matthias
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p. 5001 - 5012
(2007/10/03)
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- [Ind2TiMe2]: A general catalyst for the intermolecular hydroamination of alkynes
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[Ind2TiMe2] (Ind=indenyl) is a highly active and general catalyst for the intermolecular hydroamination of alkynes. It catalyzes the reaction of primary aryl-, tert-alkyl-, sec-alkyl-, and nalkylamines with internal and terminal alkynes. In the case of unsymmetrically substituted 1-phenyl-2-alkylalkynes, the reactions occur with modest to excellent regioselectivities, whereby formation of the anti-Markovnikov regioisomers is favored. While the major product of hydroamination reactions of terminal arylalkynes is always the anti-Markovnikov isomer, alkylalkynes react with arylamines to preferably give the Markovnikov products. To achieve reasonable rates for the addition of sterically less hindered n-alkyland benzylamines to alkynes, these amines must be added slowly to the reaction mixtures. This behavior is explained by the fact that the catalytic cycle proposed on the basis of an initial kinetic investigation includes the possibility that the rate of the reaction increases with decreasing concentration of the employed amine. Furthermore, no dimerization of the catalytically active imido complex is observed in the hydroamination of 1-phenylpropyne with 4-methylaniline in the presence of [Ind2TiMe2] as catalyst. In general, a combination of [Ind2TiMe2]-catalyzed hydroamination of alkynes with subsequent reduction leads to the formation of secondary amines with good to excellent yields. Particularly impressive is that [Ind 2TiMe2] makes it possible for the first time to perform the reactions of n-alkyl- and benzylamines with 1-phenylpropyne in a highly regioselective fashion.
- Heutling, Andreas,Pohlki, Frauke,Doye, Sven
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p. 3059 - 3071
(2007/10/03)
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- Cp*2TiMe2: An improved catalyst for the intermolecular addition of n-alkyl- and benzylamines to alkynes
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Cp*2TiMe2 has been found to be a competent catalyst for the intermolecular addition of sterically less demanding n-alkyl- and benzylamines to internal alkynes. In the presence of 2.0-6.0 mol % of the catalyst, hydroamination reactions between n-propyl-, n-hexyl-, benzyl-, p-methoxybenzyl- or 2-phenylethylamine and diphenylacetylene, 3-hexyne or 4-octyne go to completion within 24 h or less at 114°C (oil bath temperature). After subsequent reduction of the initially formed imines with zinc-modified sodium cyanoborohydride in MeOH at 25°C, the corresponding secondary amines can be isolated in excellent yields (> 78%). Hydroamination/reduction sequences employing the unsymmetrically substituted alkyne 1-phenylpropyne give access to mixtures of regioisomeric secondary amines. The observed regioselectivity is low.
- Heutling, Andreas,Doye, Sven
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p. 1961 - 1964
(2007/10/03)
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