Synthesis of 5<i>H</i>-chromeno[3,4-<i>b</i>]pyridines <i>via</i> DABCO-catalyzed [3 + 3] annulation of 3-nitro-2<i>H</i>-chromenes and allenoates
作者:Maria I. L. Soares、Clara S. B. Gomes、M. Conceição Oliveira、Joaquim Marçalo、Teresa M. V. D. Pinho e Melo
DOI:10.1039/d1ob01130h
日期:——
The DABCO-catalyzed [3 + 3] annulation between 3-nitro-2H-chromenes and benzyl 2,3-butadienoate has been developed as a route to 5H-chromeno[3,4-b]pyridine derivatives. Under optimal reaction conditions, 5H-chromeno[3,4-b]pyridines incorporating two allenoate units were obtained in moderate to good yields (30–76%). The same type of transformation could be carried out using butynoates as allene surrogates
DABCO 催化的 3-硝基-2 H-色烯和 2,3-丁二烯酸苄酯之间的 [3 + 3] 环化已被开发为生成 5 H-色烯[3,4- b ] 吡啶衍生物的途径。在最佳反应条件下,以中等至良好的产率(30-76%)获得包含两个烯丙酸酯单元的5 H-色烯[3,4- b ]吡啶。可以使用丁酸作为丙二烯替代物进行相同类型的转化。通过质谱进行的机理研究可以确定参与反应机理的关键中间体。所报道的合成方法代表了一种全新的合成 5 H -chromeno[3,4- b]吡啶核心结构基于丙二烯化学。
Efficient Preparation of TMSCCl
<sub>2</sub>
Br and Its Use in Dichlorocyclopropanation of Electron‐Deficient Alkenes
作者:Darren S. Lee、María Jesús Durán‐Peña、Laurence Burroughs、Simon Woodward
DOI:10.1002/chem.201600607
日期:2016.5.23
The reaction of excess TMSCl and LiCCl2Br at low temperature is a technically simple high yield route to TMSCCl2Br. The latter is a stable source of the dichlorobromomethide carbanion, which undergoes 1,4‐addition with cyclic nitroalkenes and (E)‐fumarates leading to dichlorocyclopropanes after bromide expulsion. For nitrostyrenes the reaction arrests at the 1,4‐addition product. Low temperature NMR
作者:Mukesh Kumar、Pankaj Chauhan、Stephen J. Bailey、Ehsan Jafari、Carolina von Essen、Kari Rissanen、Dieter Enders
DOI:10.1021/acs.orglett.8b00175
日期:2018.2.16
An efficient and highly stereoselective one-pot, four-component synthesis of functionalized tricyclic chromanes has been achieved through an organocatalyzed quadruple dominoreaction. The reaction sequence involves an oxa-Michael/Michael/Michael/aldol condensation between alcohols, 2 equiv of acrolein, and nitrochromenes to generate the pharmaceutically important tricyclic chromanes bearing three contiguous
通过有机催化的四重多米诺反应,已实现了高效且高度立体选择性的一锅四组分官能化三环苯并吡喃的合成。反应顺序包括在醇,2当量的丙烯醛和硝基色酮之间进行oxa-Michael / Michael / Michael / aldol缩合反应,以产生药学上重要的三环苯并三环苯并烷,其中包括三个连续的立体异构中心,包括手性四取代碳中心,具有良好的多米诺产量(30– 70%)和出色的非对映选择性和对映选择性(> 20:1 dr和> 99%ee)。
Enantioselective Michael reaction of 1,3-dicarbonyl compounds to 3-nitro-2H-chromenes catalyzed by chiral nickel complexes
作者:Wei-Yi Chen、Luo Ouyang、Rui-Ye Chen、Xin-Sheng Li
DOI:10.1016/j.tetlet.2010.05.111
日期:2010.7
A chiral nickel complexes-catalyzed enantioselectiveMichael addition of 1,3-dicarbonyl compounds to 3-nitro-2H-chromenes has been developed; the products could be obtained in high yields and good enantioselectivities.
Enantioselective Cascade Michael Addition/Cyclization Reactions of 3-Nitro-2<i>H</i>-Chromenes with 3-Isothiocyanato Oxindoles: Efficient Synthesis of Functionalized Polycyclic Spirooxindoles
An unprecedented Zn(OTf)2‐catalyzed asymmetric Michaeladdition/cyclization cascade of 3‐nitro‐2H‐chromenes with 3‐isothiocyanato oxindoles has been disclosed. This transformation provides an efficient access to various synthetically important polycyclic spirooxindoles in a highly stereoselective manner under mild conditions (72–99 % yields, up to >95:5 d.r. and >99 % ee). The reaction leads to the
公开了前所未有的Zn(OTf)2催化的3-硝基-2 H-色酮与3-异硫氰酸根合吲哚的不对称Michael加成/环化级联反应。这种转化可在温和条件下(72–99%的收率,高达> 95:5 dr和> 99%ee的情况下)以高度立体选择性的方式,有效地获得各种合成上重要的多环螺氧并吲哚类化合物 。该反应可在一次操作中形成三个连续的立体中心,包括1,3-不相邻的四取代碳立体中心。基于对照实验,提出了手性Zn(OTf)2 /双(恶唑啉)配合物的双功能激活模型,其中Zn II 分子部分起路易斯酸的作用,而游离NH基团的N原子通过氢键相互作用起路易斯碱的作用。