Nixarlidis Christos, Chisholm John D
Department of Chemistry, Syracuse University 1-014 Center for Science and Technology Syracuse NY 13244 USA
RSC Adv. 2024 Aug 2;14(33):24207-24211. doi: 10.1039/d4ra05265j. eCollection 2024 Jul 26.
Benzylic C-H bonds next to electron rich aromatic rings are susceptible to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) promoted functionalization. In this work benzylic carbocations formed in this manner are trapped by a pendant carboxylic acid to form a lactone. Indole-3-butyric acids are especially good substrates for the reaction. The lactonization functions well with catalytic amounts of DDQ combined with MnO as the stoichiometric oxidant. This cyclization proceeds with a number of indole-3-butyric acids, and yields were generally good as long as the indole was electron rich and free of bulky substituents near the reacting benzylic carbon. Indole-3-butyric acids functionalized with electron withdrawing groups tend to give more moderate yields. Other aromatic substrates also participate as long as the aromatic ring is functionalized with electron donating groups.
富电子芳香环邻位的苄基碳氢键易于发生2,3-二氯-5,6-二氰基-1,4-苯醌（DDQ）促进的官能化反应。在本工作中，以这种方式形成的苄基碳正离子被一个悬垂的羧酸捕获，从而形成内酯。吲哚-3-丁酸是该反应特别好的底物。使用催化量的DDQ与化学计量的氧化剂MnO相结合，内酯化反应效果良好。这种环化反应适用于多种吲哚-3-丁酸，只要吲哚富电子且反应苄基碳附近没有庞大的取代基，产率通常都很高。用吸电子基团官能化的吲哚-3-丁酸往往产率适中。只要芳香环用供电子基团官能化，其他芳香底物也能参与反应。
