- DFT-Guided Phosphoric-Acid-Catalyzed Atroposelective Arene Functionalization of Nitrosonaphthalene
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Guided by computational design, Tan and colleagues disclose a chiral phosphoric-acid-catalyzed asymmetric functionalization of naphthalenes with nitroso as the activating and directing group. This nucleophilic aromatic substitution reaction allows divergent access to two types of axially chiral arylindole frameworks with wide substrate generality under excellent enantiocontrol and, more importantly, offers a facile approach to the privileged NOBIN (2-amino-2′-hydroxy-1,1′-binaphthyl) structures. DFT calculations illustrate the plausible reaction pathway and provide additional insights into the origins of enantioselectivity.Functionalization of arenes represents the most efficient approach for constructing a core backbone of important aryl compounds. Compared with the well-developed electrophilic aromatic substitution and transition-metal-catalyzed C–H activation, nucleophilic aromatic substitution remains challenging because of the lack of a convenient route for rapid conversion of the σH adduct to other stable and versatile intermediates in situ. Guided by computational design, we were able to realize asymmetric nucleophilic aromatic substitution by introducing a nitroso group on naphthalene via chiral phosphoric acid catalysis. This strategy enables efficient construction of atropisomeric indole-naphthalenes and indole-anilines with excellent stereocontrol. Density functional theory (DFT) calculations provide further insights into the origins of enantioselectivity and the reaction mechanisms. The successful application in the synthesis of NOBINs (2-amino-2′-hydroxy-1,1′-binaphthyl) extends the utility of this strategy.Highly efficient conversion of inexpensive and readily available arene materials into high-value-added chiral molecules is of great importance in modern synthetic chemistry given the enormous potential of such structures in functional materials, pharmaceuticals, and other relevant chemical industries. Organocatalytic nucleophilic aromatic substitution enabled by an azo group offers an effective approach to enantioselective functionalization of naphthalene C–H bonds featuring an intramolecular oxidation of an unstabilized σH adduct. Premised on density functional theory (DFT) calculations, nitroso has emerged as another promising activating and oxidative group, whose synthetic potential is substantiated in the atroposelective synthesis of several groups of representative biaryl atropisomers processed by a chiral phosphoric acid catalyst. The success of this reaction explicitly exemplifies the ability of computational tools to streamline organic synthesis with intensified robustness in the disclosed strategy.
- Ding, Wei-Yi,Yu, Peiyuan,An, Qian-Jin,Bay, Katherine L.,Xiang, Shao-Hua,Li, Shaoyu,Chen, Ying,Houk,Tan, Bin
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p. 2046 - 2059
(2020/07/13)
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- Palladium-Catalyzed C–C Ring Closure in α-Chloromethylimines: Synthesis of 1H-Indoles
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The C-C ring closure of α-chloromethyl alkyl or aryl N-aryl imines catalyzed with 1 to 10 % Pd(OAc)2/P(p-tolyl)3 afford efficiently 2-aryl- and 2-alkyl-1H-indoles. The heterocyclization reaction involves the initial formation of [2-(arylimino)ethyl]palladium(II) chloride complexes with subsequent C-H activation of the aromatic amine ring. Readily or commercially available α-chloromethyl-aryl or -alkyl ketones are used as the precursors. Functionalized indoles at the benzene ring are obtained when the imines are derived from substituted anilines.
- Bellezza, Delia,Noverges, Bárbara,Fasano, Francesco,Sarmiento, Jeymy T.,Medio-Simón, Mercedes,Asensio, Gregorio
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p. 1229 - 1235
(2019/01/04)
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- Rhodium(III)-catalyzed c-h activation and indole synthesis with hydrazone as an auto-formed and auto-cleavable directing group
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An efficient, practical, and external-oxidant-free indole synthesis from readily available aryl hydrazines was developed, by using hydrazone as a directing group for RhIII-catalyzed C-H activation and alkyne annulation. The hydrazone group was formed by in situ condensation of hydrazines and Ci£O source, whereas its N-N bond was served as an internal oxidant, for which we termed it as an auto-formed and auto-cleavable directing group (DGauto). This method needs no step for pre-installation and post-cleavage of the directing group, making it a quite easily scalable approach to access unprotected indoles with high step economy. The DGauto strategy was also applicable for isoquinoline synthesis. In addition, synthetic utilities of this chemistry for rapid assembly of π-extended nitrogen-doped polyheterocycles and bioactive molecules were demonstrated. Copyright
- Zheng, Liyao,Hua, Ruimao
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supporting information
p. 2352 - 2356
(2014/03/21)
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- InBr3-promoted divergent approach to polysubstituted indoles and quinolines from 2-ethynylanilines: Switch from an intramolecular cyclization to an intermolecular dimerization by a type of terminal substituent group
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(Chemical Equation Presented) Use of a 2-ethynylaniline having an alkyl or aryl group on the terminal alkyne selectively produced a variety of polyfunctionalized indole derivatives in moderate to excellent yields via indium-catalyzed intramolecular cyclization of the corresponding alkynylaniline. In contrast, employment of a substrate with a trimethylsilyl group or with no substituent group on the terminal triple bond, exclusively afforded polysubstituted quinoline derivatives in good yields via indium-promoted intermolecular dimerization of the ethynylaniline. This indium catalytic system successfully accommodated the intramolecular cyclization of other arylalkyne skeletons involving a carboxylic acid and an amide group.
- Sakai, Norio,Annaka, Kimiyoshi,Fujita, Akiko,Sato, Asuka,Konakahara, Takeo
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p. 4160 - 4165
(2008/09/21)
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- InBr3-catalyzed intramolecular cyclization of 2-alkynylanilines leading to polysubstituted indole and its application to one-pot synthesis of an amino acid precursor
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We describe InBr3-catalyzed cyclization of 2-alkynylaniline derivatives having a variety of functional groups producing polysubstituted indoles. This methodology could be applied to the one-pot synthesis of an amino acid precursor by the addition of a catalytic amount of the indium salt, an imine, and TMSCl.
- Sakai, Norio,Annaka, Kimiyoshi,Konakahara, Takeo
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p. 631 - 634
(2007/10/03)
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