Highly Diastereo- and Enantioselective Additions of Homoenolates to Nitrones Catalyzed by <i>N</i>-Heterocyclic Carbenes
作者:Eric M. Phillips、Troy E. Reynolds、Karl A. Scheidt
DOI:10.1021/ja710521m
日期:2008.2.1
diastereo- and enantioselective addition of N-heterocyclic carbene-generated homoenolates to nitrones is reported. This formal [3 + 3] addition of α,β-unsaturatedaldehydes and nitrones generates unusual morpholinone heterocycles which are converted into γ-hydroxy amino esters by addition of methanol to the reaction. The use of a chiral N-heterocyclic carbene (NHC) as the catalyst provides the amino esters
Gold‐Catalyzed Bicyclic and [3+2]‐Annulations of Internal Propargyl Alcohols with Nitrones and Imines To Yield to Two Distinct Heterocycles
作者:Sayaji Arjun More、Tzu‐Hsuan Chao、Mu‐Jeng Cheng、Rai‐Shung Liu
DOI:10.1002/adsc.202001119
日期:2021.1.19
4‐a]indoles from 1‐oxo‐3‐yn‐4‐ols and nitrones is described; this new bicyclic annulation presents the first examples that internal alkynes can react with nitrones to undergo an oxoarylation route. DFT calculations indicate a [3,3]‐sigmatropic shift of initial alkenylgold intermediates to elude the intermediacy of gold carbenes. We also developed new [3+2]‐annulations of the same 1‐oxo‐3‐yn‐4‐ols with imines
描述了一种由金催化的由1-氧代3-yn-4-醇和硝酮合成的1,3-二氢恶唑并[3,4- a ]吲哚的方法;这种新的双环环化反应是第一个实例,表明内部炔烃可以与硝酮反应进行羰基化反应。DFT计算表明,初始烯基金中间体发生了[3,3]-σ位移,从而避开了金卡宾的中间产物。我们还用亚胺开发了相同的1-oxo-3-yn-4醇与新的[3 + 2]环,有效地生成了oxazolidin-4-yylne衍生物。这些1-oxo-3-ynes的束缚醇可捕获其亚稳的2-azadienium中间体,从而实现新颖的环化反应。我们的机械分析表明,尽管两种产品在结构上相关,但它们是由两个独立的系统生产的。
A series of chiral 4,5-bis(2-oxazolinyl)-(2,7-di-tert-butyl-9,9-dimethyl)-9H-xanthenes (xabox) and their transition-metal complexes were synthesized. The X-ray analysis of xabox–RhCl3 complex shows a unique facial type structure. Xabox–Bn–Mn(II) and xabox–Bn–Mg(II) complexes were found to be efficient catalysts in nitrone 1,3-dipolarcycloaddition (1,3-D.C.) reaction resulting in good to excellent
合成了一系列手性的4,5-双(2-恶唑啉基)-(2,7-二叔丁基-9,9-二甲基)-9 H-黄嘌呤(xabox)及其过渡金属配合物。Xabox–RhCl 3复合物的X射线分析显示出独特的面部类型结构。发现Xabox–Bn–Mn(II)和xabox–Bn–Mg(II)配合物是硝酮1,3-偶极环加成(1,3-DC)反应的有效催化剂,对映选择性优良,极佳,范围从96: 4至> 99:图10F内型/外型比和91-96%ee的对内切加合物。硝酮1,3-DC反应中配体的对映体过量与产物之间的相关性显示出明显的线性关系,这表明xabox-金属催化剂可以用作单分子催化剂。此外,还发现xabox - i -Pr-Mn(II)配合物是丙烯酰恶唑烷酮与环戊二烯Diels-Alder(D-A)反应的活性催化剂,定量提供了相应的环加合物,ee和98%对应,98 :2内/外比。
Highly selective 1,3-dipolar cycloadditions of captodative olefins 1-acetylvinyl carboxylates to diverse dipoles
Regioselective 1,3-dipolarcycloadditions of captodative 1-acetylvinyl p-nitrobenzoyloxy (1a) with propionitrile oxide, diphenylnitrile imine and diazoalkanes provided the corresponding 5-acetyl- isoxazoles and pyrazoles. Evidence to support the formation of the initial cycloadducts was obtained. The addition of nitrones also proved to be highly regio- and stereoselective.
Synthesis of novel chiral bis(2-oxazolinyl)xanthene (xabox) ligands and their evaluation in catalytic asymmetric 1,3-dipolar cycloaddition reactions of nitrones with 3-crotonoyl-2-oxazolidinone
Chiral 4,5-bis(2-oxazolinyl)-(2,7-di-tert-butyl-9,9-dimethyl)-9H-xanthenes (xabox) were synthesized and the chiral environments were evaluated in catalytic asymmetric 1,3-dipolarcycloaddition reactions of nitrones resulting in good to excellent enantioselectivities. 1,3-Dipolarcycloaddition reactions of nitrones with 3-crotonoyl-2-oxazolidinone in the presence of a bis(2-oxazolinyl)xanthene (4c;