Iron and Ruthenium Lewis Acid Catalyzed Asymmetric 1,3-Dipolar Cycloaddition Reactions between Nitrones and Enals
作者:Florian Viton、Gérald Bernardinelli、E. Peter Kündig
DOI:10.1021/ja017814f
日期:2002.5.1
The single coordination-site transition metal Lewisacids [CpM(BIPHOP-F)][SbF6] (M = Fe, Ru) catalyze the [3+2] dipolar cycloadditionreaction between reactive nitrones and alpha,beta-unsaturated aldehydes to give chiral isoxazolidines with ee values of 75 to >96%. The stereochemistry of the major enantiomer is consistent with an endo approach of the nitrone to the Calpha-Si-face of the enal in the s-trans
6H(2)O catalyzed the 1,3-cycloaddition between nitrones 3 with alkylidene malonates 2 at 0 degrees C to give the isoxazolidines with both high enantioselectivity and high exo selectivity. However, when the temperature was lowered from 0 to -40 degrees C, the same cycloaddition afforded endo isomers as the major products with good to high enantioselectivity. A mechanism is provided.
of a chiral C2-symmetric bis(oxazoline) ligand, its Lewis acid complexes-catalyzed asymmetric 1,3-dipolarcycloaddition reactions of nitrones with electron-deficient dipolarophiles, 3-(2-alkenoyl)-1,3-oxazolidin-2-ones, have been investigated and it was found that the cycloadditions using a Cu(II)-bis(oxazoline) complex under optimized reaction conditions induced extremely high enantioselectivity.
Nitrones as Trapping Reagents of α,β-Unsaturated Carbene Intermediates - [1,2]Oxazino[5,4-<i>b</i>]indoles by a Platinum- Catalyzed Intermolecular [3+3] Cycloaddition
作者:Weibo Yang、Tao Wang、Yang Yu、Shuai Shi、Tuo Zhang、A. Stephen K. Hashmi
DOI:10.1002/adsc.201300338
日期:2013.5.17
Boc‐protected 2‐(3‐methoxy‐1‐propynyl)anilines and nitrones in platinum‐catalyzed reactions deliver [1,2]oxazino[5,4‐b]indoles. Twelve examples with yields of 41–95% are reported. Different substituents like nitro, trifluoromethyl, fluoro, bromo, and ester groups are tolerated. With regard to the mechanism, this reaction probably combines an initial intramolecular cyclization/elimination to vinylcarbenoid
在铂催化的反应中,一些容易获得的Boc保护的2-(3-甲氧基-1-丙炔基)苯胺和硝酮可提供[1,2]恶嗪基[5,4- b ]吲哚。报道了十二个产量为41–95%的例子。可以容忍不同的取代基,例如硝基,三氟甲基,氟,溴和酯基。关于机理,该反应可能结合了最初的分子内环化/消除为乙烯基类胡萝卜素物质,以及随后与硝酮的逐步的分子间[3 + 3]环加成反应。
Trifluoromethyl Vinyl Sulfide: A Building Block for the Synthesis of CF<sub>3</sub>S-Containing Isoxazolidines
作者:Alejandra Riesco-Domínguez、Jeroen van de Wiel、Trevor A. Hamlin、Bas van Beek、Stephen D. Lindell、Daniel Blanco-Ania、F. Matthias Bickelhaupt、Floris P. J. T. Rutjes
DOI:10.1021/acs.joc.7b02639
日期:2018.2.16
Trifluoromethyl vinyl sulfide, a potential building block for pharmaceutically and agrochemically relevant products, is prepared and used for the first time in high-pressure-mediated 1,3-dipolar cycloaddition reactions with nitrones to synthesize (trifluoromethyl)sulfanyl isoxazolidines.