New Reactions of -Halocarbanions: Simple Synthesis of Substituted Tetrahydrofurans
作者:Mieczysław M??kosza、Marek Judka
DOI:10.1002/1521-3765(20020916)8:18<4234::aid-chem4234>3.0.co;2-g
日期:2002.9.16
gamma-halocarbanions that undergo fast intramolecular substitution of the halogen to produce substituted cyclopropanes. We found that these short-lived carbanionic intermediates can be trapped with active external electrophilic partners, such as aldehydes, to give the aldol anions. These anions then undergo rapid intramolecular substitution of chloride to produce 2,3-disubstituted tetrahydrofurans. Under the right
用碱处理4-氯丁腈,3-氯丙基苯基砜和其他相关化合物可得到γ-卤代碳阴离子,其经过卤素的分子内快速取代以生成取代的环丙烷。我们发现,这些短寿命的碳负离子中间体可以被活性的外部亲电子伴侣(例如醛)捕获,从而得到醛醇阴离子。然后,这些阴离子快速进行氯的分子内取代,从而生成2,3-二取代的四氢呋喃。在适当的条件下,四氢呋喃的收率非常好。与酮的类似反应产生2,2,3-三取代的呋喃,但该方法通常效率较低。通过竞争实验定性地估计分子内和分子间过程的速率之间的比率。