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.
Cooperative Silver- and Base-Catalyzed Diastereoselective Cycloaddition of Nitrones with Methylene Isocyanides: Access to 2-Imidazolinones
作者:Yan Chen、Yijing Wu、Andrey Shatskiy、Yuhe Kan、Markus D. Kärkäs、Jian-Quan Liu、Xiang-Shan Wang
DOI:10.1002/ejoc.202000437
日期:2020.6.23
A protocol involving cooperative silver‐ and base‐catalyzed diastereoselective cycloaddition of nitrones with isocyanides is described, delivering several valuable 2‐imidazolinones derivatives as single diastereomers. A plausible reaction mechanism is rationalized by DFT calculations. DBU plays dual roles in the developed reaction, acting as both the base and ligand.
<sup>13</sup>C and<sup>1</sup>H NMR of Arylnitrones. Substituent Effects of α-Phenyl-<i>N</i>-(<i>p</i>-substituted phenyl)nitrones
作者:Kohji Suda、Toshio Tsujimoto、Masashige Yamauchi
DOI:10.1246/bcsj.60.3607
日期:1987.10
Substituent effects on the chemical shifts of the conjugation sites in α-phenyl-N-arylnitrones (2) have been investigated. Resonance effects predominate at these positions. The electronic effects of the substituents should be treated separately between electron-donating groups and electron-withdrawing ones. A plausible mechanism for the transmission of the substituent effects in 2 has been proposed.
Highly Diastereoselective Gold- or Copper-Catalyzed Formal [4+3] Cycloaddition of 1-(1-Alkynyl) Cyclopropyl Ketones and Nitrones
作者:Yu Bai、Jie Fang、Jun Ren、Zhongwen Wang
DOI:10.1002/chem.200901133
日期:2009.9.14
Domino day: A highlydiastereoselective Cu‐ or Au‐catalyzed tandem cycloisomerization/formal [4+3] cycloaddition of 1‐(1‐alkynyl) cyclopropylketones and nitrones has been developed (see scheme) along with an efficient one‐pot, three‐component version of this reaction. This methodology provides a route to a new type of 5/7‐bicyclic heterocycle: a furan‐fused oxazepine.
Chiral tris(oxazoline)/Cu(ii) catalyzed coupling of terminal alkynes and nitronesElectronic supplementary information (ESI) available: experimental. See http://www.rsc.org/suppdata/cc/b3/b306653c/
Novel chiral iPr-tris(oxazoline)/Cu(ClO4)2 x 6H2O catalyzedcoupling of terminal acetylenes and nitrones to afford cis-disubstituted beta-lactams is described; the choice of base proves essential to both the diastereoselectivity and the enantioselectivity.
描述了新颖的手性iPr-三(恶唑啉)/ Cu(ClO4)2 x 6H2O催化的末端乙炔和硝酮的偶联,得到顺式二取代的β-内酰胺。碱的选择被证明对非对映选择性和对映选择性都是必不可少的。