- Regio- and Enantioselective (3+3) Cycloaddition of Nitrones with 2-Indolylmethanols Enabled by Cooperative Organocatalysis
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The regio- and enantioselective (3+3) cycloaddition of nitrones with 2-indolylmethanols was accomplished by the cooperative catalysis of hexafluoroisopropanol (HFIP) and chiral phosphoric acid (CPA). Using this approach, a series of indole-fused six-membered heterocycles were synthesized in high yields (up to 98 %), with excellent enantioselectivities (up to 96 % ee) and exclusive regiospecificity. This approach enabled not only the first organocatalytic asymmetric (3+3) cycloaddition of nitrones but also the first C3-nucleophilic asymmetric (3+3) cycloaddition of 2-indolylmethanols. More importantly, theoretical calculations elucidated the role of the cocatalyst HFIP in helping CPA control the reactivity and enantioselectivity of the reaction, demonstrating a new mode of cooperative catalysis.
- Li, Tian-Zhen,Liu, Si-Jia,Sun, Yu-Wen,Deng, Shuang,Tan, Wei,Jiao, Yinchun,Zhang, Yu-Chen,Shi, Feng
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supporting information
p. 2355 - 2363
(2020/12/09)
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- Crystal and molecular structure studies of (Z)-N-methyl-C-4-substituted phenyl nitrones by XRD, DFT, FTIR and NMR methods
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(Z)-N-methyl-C-4-substituted phenyl nitrones –O+N(Me)=C(H)R (Z-2a R = 4-ClC6H4, Z-2b R = 4-NO2C6H4, Z-2c R = 4-CH3OC6H4) were synthesized and cha
- Lasri, Jamal,Eltayeb, Naser Eltaher,Haukka, Matti,Alghamdi, Yousef
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- A magnetoclick imidazolidinone nanocatalyst for asymmetric 1,3-dipolar cycloadditions
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A 1,3-dipolar azide-alkyne cycloaddition has been used to prepare a magnetic nanoparticle immobilized MacMillan catalyst that catalyzes the enantioselective 1,3-dipolar cycloaddition between nitrones and α,β-unsaturated aldehydes. The catalyst can be recovered and recycled for five consecutive runs without any significant loss in yields and diastereo- and enantioselectivities of the isoxazolidines. Copyright
- Pagoti, Sreenivasarao,Dutta, Debasish,Dash, Jyotirmayee
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supporting information
p. 3532 - 3538
(2014/01/06)
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- N-tert-Butyl and N-methyl nitrones derived from aromatic aldehydes inhibit macromolecular permeability increase induced by ischemia/reperfusion in hamsters
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N-Alquil nitrones 1c and 3-6 were prepared from aromatic aldehydes and N-tert-butylhydroxylamine or N-methylhydroxylamine in good yields and soft conditions. Their protective effect against microvascular damages caused by ischemia/reperfusion in 'hamster
- Dias, Ayres G.,Santos, Carlos E.V.,Cyrino, Fatima Z.G.A.,Bouskela, Eliete,Costa, Paulo R.R.
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experimental part
p. 3995 - 3998
(2009/10/17)
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- 1,3-Dipolar cycloadditions. Part XVII: Experimental and theoretical spectroscopic investigations of C-aryl-N-methyl nitrones
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Detailed experimental and theoretical spectroscopic studies of C-aryl-N-methyl nitrones have been reported. The optimized geometries have been calculated by DFT/B3LYP level of theory with 6-31+G(d,p) basis set. The theoretically computed frontier orbital
- Acharjee, Nivedita,Banerji, Avijit,Banerjee, Manas,Das, Tapas K.
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body text
p. 1627 - 1637
(2010/06/17)
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- Exploiting microwave-assisted neat procedures: synthesis of N-aryl and N-alkylnitrones and their cycloaddition en route for isoxazolidines
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Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of α-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate.
- Andrade, Marta M.,Barros, Maria Teresa,Pinto, Rui C.
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p. 10521 - 10530
(2008/12/23)
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- Oxidation of N-benzyl-N-methylhydroxylamines to nitrones. A mechanistic study
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Oxidation of various N-(o-, m-, p- substituted benzyl)- N-methylhydroxylamines has been carried out using mercury(II) oxide and p-benzoquinone (p-BQ) as oxidants. Hammett plots have been obtained with negative ρ values, showing the development of a positive centre in the transition state. The unstable E nitrones, which readily isomerize to the more stable Z nitrones, are obtained in appreciable quantities and in some cases as the major product. A considerable deuterium isotope effect is observed in the oxidation process. The overall picture of the mechanistic pathway involves electron transfer from nitrogen to the oxidant followed by hydrogen abstraction.
- Hassan, Azfar,Wazeer, Mohammed I. M.,Ali, Sk. Asrof
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p. 393 - 399
(2007/10/03)
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- Chromium and Tungsten Pentacarbonyl Groups as Reactivity and Selectivity Auxiliaries in Cycloaddition of Alkynyl Fischer Carbene Complexes with N-Alkyl Nitrones
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Alkynyl Fischer carbene complexes were found to undergo chemoselective, regioselective, and rate-enhanced 1,3-dipolar cycloaddition with nitrones to give 2,3-dihydroisoxazole carbene complexes in excellent yields.These alkynyl complexes can serve as synth
- Chan, Kin Shing,Yeung, Ming Lok,Chan, Wai-kin,Wang, Ru-Ji,Mak, Thomas C. W.
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p. 1741 - 1747
(2007/10/02)
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