乙醇(3b)抑制烷基卤化物1在超临界二氧化碳(sc CO 2)中的S N 1反应,并且不产生醚类产物。酒精3在卤代烃1与1,3-二甲氧基苯(2)在sc CO 2中的不同条件下反应的意外行为,通过Brønsted和Lewis酸碱平衡试剂,中间体,添加剂和产物的合理化得到了合理化。一种具有以下特征的奇异溶剂:(i)二氧化碳的强四极杆和路易斯酸特性,阻碍了S N通过强力溶解基本溶质的2条路径; (ii)二氧化碳的弱路易斯碱特性,阻止其表现为质子吸收体;(iii)sc CO 2的可压缩性质,其在溶剂需求速率确定步骤中增强了优先溶剂化对二氧化碳可利用性的影响。
Alcohols react with arenes in the presence of cationic iron(III) porphyrin catalyst. The reaction involves the formation of the C–C bond via dehydration, which is formal Lewis acid catalyzed Friedel–Craftsreaction.
Supercritical Carbon Dioxide: A Promoter of Carbon-Halogen Bond Heterolysis
作者:Thais Delgado-Abad、Jaime Martínez-Ferrer、Ana Caballero、Andrea Olmos、Rossella Mello、María Elena González-Núñez、Pedro J. Pérez、Gregorio Asensio
DOI:10.1002/anie.201303819
日期:2013.12.9
Amazing reaction medium: Supercritical carbon dioxide, with zero dipole moment, lower dielectric constant than pentane, and non‐hydrogen‐bonding behavior, ionizes carbon–halogen bonds, dissociates the resulting ion pairs, and escapes from capture by the carbocation intermediates at temperatures above 40 °C. These properties allow the observation of carbocation chemistry in the absence of acids.
between electron rich arenes and benzylic alcohols or ethers, catalysed by gold(III) salts, or other catalysts such as gold(I) and iron (III), and its application to the regio- and stereoselective synthesis of procyanidinsdimers B1 and B3.