- Iron-Catalyzed Cycloaddition of Amides and 2,3-Diaryl-2 H-azirines to Access Oxazoles via C-N Bond Cleavage
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A novel and efficient iron-catalyzed cycloaddition reaction using readily available 2,3-diaryl-2H-azirines and primary amides is reported. A wide range of trisubstituted oxazoles could be achieved in good yields with good functional group compatibility. In this transformation, two C-N bonds were cleaed and new C-N and C-O bonds were formed.
- Zhao, Mi-Na,Ning, Gui-Wan,Yang, De-Suo,Fan, Ming-Jin,Zhang, Sheng,Gao, Peng,Zhao, Li-Fang
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p. 2957 - 2964
(2021/02/01)
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- Lewis acid-mediated defluorinative [3+2] cycloaddition/aromatization cascade of 2,2-difluoroethanol systems with nitriles
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The properties of C?F bonds, including high thermal and chemical stability, make derivatization of organic fluorine-containing compounds by the activation of the C?F bond and subsequent functionalization quite challenging. We herein report a Lewis acid-mediated defluorinative cycloaddition/aromatization cascade of 2,2-difluoroethanols with nitriles as a novel synthetic method for the preparation of 2,4,5-trisubstituted oxazoles. This reaction, which involves cleavage of two C?F bonds and the consecutive formation of C?O and C?N bonds in a one-pot fashion, features a broad substrate scope and moderate to high reaction yields. Mechanistic studies revealed that the reaction is initiated by the Lewis acid-mediated ring closure of the 2,2-difluoroethanol to produce the fluoroepoxide intermediate. (Figure presented.).
- Hsieh, Min-Tsang,Lee, Kuo-Hsiung,Kuo, Sheng-Chu,Lin, Hui-Chang
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p. 1605 - 1610
(2018/03/05)
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- A Divergent Approach to Indoles and Oxazoles from Enamides by Directing-Group-Controlled Cu-Catalyzed Intramolecular C-H Amination and Alkoxylation
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A directing-group-controlled, copper-catalyzed divergent approach to indoles and oxazoles from enamides has been developed. The picolinamide-derived enamides undergo the intramolecular aromatic C-H amination in the presence of a Cu(OPiv)2 catalyst and an MnO2 oxidant to form the corresponding indoles in good yields. On the other hand, simpler aryl- or alkyl-substituted enamides are converted to the 2,4,5-trisubstituted oxazole frameworks via vinylic C-H alkoxylation under identical conditions. The copper catalysis can provide uniquely divergent access to indole and oxazole heteroaromatic cores of great importance in medicinal and material chemistry.
- Yamamoto, Chiaki,Takamatsu, Kazutaka,Hirano, Koji,Miura, Masahiro
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p. 9112 - 9118
(2017/09/11)
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- Preparation of substituted oxazoles by ritter reactions of α-oxo tosylates
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The Lewis acid catalyzed Ritter reaction of α-oxo tosylates with nitriles forms the basis of an efficient synthesis of oxazoles. Oxazoles with various substituents can be readily prepared from inexpensive starting materials. Georg Thieme Verlag Stuttgart.
- Lai, Ping-Shan,Taylor, Mark S.
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experimental part
p. 1449 - 1452
(2010/09/14)
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- Ceric ammonium nitrate promoted oxidation of oxazoles
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The ceric ammonium nitrate promoted oxidations of 4,5-diphenyloxazoles and oxazoles with various substitution patterns have been investigated. This transformation results in the formation of the corresponding imide in good yield and tolerates a wide variety of functional groups and substituents on the oxazole moiety.
- Evans, David A.,Nagorny, Pavel,Xu, Risheng
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p. 5669 - 5671
(2007/10/03)
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