Base-Mediated Carboxylation of Unprotected Indole Derivatives with Carbon Dioxide

Abstract

A simple and straightforward method for the preparation of indole-3-carboxylic acids was discovered through the direct carboxylation of indoles with atmospheric pressure of carbon dioxide (CO(2)) under basic conditions. The key for the reaction was found to be the use of a large excess of LiO(t)Bu as a base to suppress the undesired decarboxylation side reaction.

Roles of Bases in Transition-Metal Catalyzed Organic Reactions

“…图 3 叔丁醇锂作用下的吲哚 3 位羧基化反应 [5] Figure 3 Direct carboxylation of indole mediated by LiOBu-t [5] 碱在溶液中的状态也会影响反应的结果. 刘磊等 [6] 为解决反应中无机碱在有机溶剂中的溶解度不好的问 题, 设计合成了离子型有机碱(由大位阻有机阳离子和 碱性阴离子组成, 如图 4 所示).…”

C−H Carboxylation of Aromatic Compounds through CO2 Fixation

“…In 2012, the Kobayashi group found that LiO t Bu allowed the formation of indole‐3‐carboxylic acid derivatives under ambient CO 2 atmosphere 15. Interestingly, the authors found the use of a large excess of LiO t Bu (5 equiv) was essential to prevent competing product decarboxylation and to improve yields and reproducibility.…”

Direct Carboxylation of C(sp3)-H and C(sp2)-H Bonds with CO2 by Transition-Metal-Catalyzed and Base-Mediated Reactions

“…(Scheme 60) [140]. Under optimized conditions (ambient CO2 pressure, 100 °C) the use of a large excess of LiO t Bu was found (5 eq.)…”