Cascade Oxa-Michael–Henry Reaction of Salicylaldehydes with Nitrostyrenes via Ball Milling: A Solvent-Free Synthesis of 3-Nitro-2H-chromenes
摘要:
Cascade oxa-Michael-Henry reactions of salicylaldehyde derivatives with beta-nitrostyrenes catalyzed by potassium carbonate via solvent-free ball milling are demonstrated. The corresponding 3-nitro-2H-chromene products were obtained in moderate to excellent yields. This method offers significant advantages, particularly in terms of high yields, short reaction times and mild conditions.
Augmentation of Enantioselectivity by Spatial Tuning of Aminocatalyst: Synthesis of 2-Alkyl/aryl-3-nitro-2<i>H</i>-chromenes by Tandem Oxa-Michael–Henry Reaction
作者:Rahul Mohanta、Ghanashyam Bez
DOI:10.1021/acs.joc.9b03366
日期:2020.4.3
The asymmetric oxa-Michael addition of salicylaldehyde to conjugatednitroalkenes often suffers from poor reactivity and selectivity and a long reaction time. Because of the formation of an iminium ion with aminocatalyst, the nucleophilicity of the phenolic hydroxy group in salicylaldehyde reduces further to make the oxa-Michael reaction reversible. Here, we report a structurally simple and easily
The asymmetric domino reaction of various 3-nitro-2H-chromene derivatives 2 to 3-isothiocyanato oxindole 3 with moderate to good enantioselectivities, employing readily available bifunctionalthiourea 1d as the organocatalyst, was described. A series of chiral multi-functionalized tetracyclic spiro[chromeno[3,4-c] pyrrole-1,3′-indoline] derivatives with four vicinal chiral carbon centers including
描述了使用容易获得的双官能硫脲1d作为有机催化剂,具有中等到良好对映选择性的各种3-硝基-2 H-色烯衍生物2到3-异硫氰酸根合吲哚3的不对称多米诺反应。成功制备了一系列手性多官能化的四环螺[chromeno [3,4- c ]吡咯-1,3'-二氢吲哚]衍生物,其具有四个相邻的手性碳中心,包括两个四级立体中心。值得注意的是,在温和条件下,产物5可以在乙醇中干净地转化为化合物4。