- Taking diazo transfer to water: α-diazo carbonyl compounds from in situ generated mesyl azide
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Mesyl azide generated in situ in aqueous medium converted a range of active methylene substrates into the corresponding diazo compounds in good yields and high purity with no need for chromatographic purification. The products thus obtained are suitable for the subsequent RhII-catalyzed O–H insertions with no need for chromatography in the interim.
- Dar'in, Dmitry V.,Krasavin, Mikhail,Shevalev, Robert M.,Zhmurov, Petr A.
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p. 372 - 373
(2020/06/19)
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- α-Alkylidene-γ-butyrolactone Formation via Bi(OTf)3-Catalyzed, Dehydrative, Ring-Opening Cyclizations of Cyclopropyl Carbinols: Understanding Substituent Effects and Predicting E/Z Selectivity
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A Bi(OTf)3-catalyzed ring-opening cyclization of (hetero)aryl cyclopropyl carbinols to form α-alkylidene-γ-butyrolactones (ABLs) is reported. This transformation represents different chemoselectivity from previous reports that demonstrated formation of (hetero)aryl-fused cyclohexa-1,3-dienes upon acid-promoted cyclopropyl carbinol ring opening. ABLs are obtained in up to 89% yield with a general preference for the E-isomers. Mechanistically, Bi(OTf)3 serves as a stable and easy to handle precursor to TfOH. TfOH then catalyzes the formation of cyclopropyl carbinyl cations, which undergo ring opening, intramolecular trapping by the neighboring ester group, subsequent hydrolysis, and loss of methanol resulting in the formation of the ABLs. The nature and relative positioning of the substituents on both the carbinol and the cyclopropane determine both chemo- and stereoselective outcomes. Carbinol substituents determine the extent of cyclopropyl carbinyl cation formation. The cyclopropane donor substituents determine the overall reaction chemoselectivity. Weakly stabilizing or electron-poor donor groups provide better yields of the ABL products. In contrast, copious amounts of competing products are observed with highly stabilizing cyclopropane donor substituents. Finally, a predictive model for E/Z selectivity was developed using DFT calculations.
- Sandridge, Matthew J.,McLarney, Brett D.,Williams, Corey W.,France, Stefan
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p. 10883 - 10897
(2017/10/27)
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- Rh(III)-Catalyzed Regio- and Chemoselective [4 + 1]-Annulation of Azoxy Compounds with Diazoesters for the Synthesis of 2H-Indazoles: Roles of the Azoxy Oxygen Atom
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A Rh(III)-catalyzed tandem C-H alkylation/intramolecular decarboxylative cyclization of azoxy compounds with diazoesters for the synthesis of 3-acyl-2H-indazoles is disclosed. The azoxy instead of the azo group enables a distinct approach for cyclative capture, leading to a [4 + 1]-annulation rather than a classic [4 + 2] manner. The azoxy oxygen atom is traceless after annulation, and further removal from the product is not required. This reaction features a complete regioselectivity for unsymmetrical azoxybenzenes and a compatibility of monoaryldiazene oxides.
- Long, Zhen,Wang, Zhigang,Zhou, Danni,Wan, Danyang,You, Jingsong
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supporting information
p. 2777 - 2780
(2017/06/07)
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- Stereoselective synthesis of 4-substituted-cyclic sulfamidate-5-carboxylates by asymmetric transfer hydrogenation accompanied by dynamic kinetic resolution and applications to concise stereoselective syntheses of (-)-epi-cytoxazone and the taxotere side-c
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Dynamic kinetic resolution driven, asymmetric transfer hydrogenation reactions of cyclic sulfamidate imine-5-carboxylate esters were developed. Applications of the new methodology to stereoselective syntheses of the taxotere side-chain and (-)-epi-cytoxaz
- Kim, Jin-Ah,Seo, Yeon Ji,Kang, Soyeong,Han, Juae,Lee, Hyeon-Kyu
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supporting information
p. 13706 - 13709
(2015/01/09)
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- N-H Insertion reactions of rhodium carbenoids. Part 5: A convenient route to 1,3-azoles
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Dirhodium(II) carboxylate catalysed reaction of diazocarbonyl compounds 2 in the presence of primary amides 1 results in the formation of α-acylaminoketones 3 (12 examples) by N-H insertion reaction of the intermediate rhodium carbene. The 1,4-dicarbonyl
- Davies, James R.,Kane, Peter D.,Moody, Christopher J.
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p. 3967 - 3977
(2007/10/03)
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