Access to Indoles via Diels-Alder Reactions of 5-Methylthio-2-vinylpyrroles with Maleimides
作者:Wayland E. Noland、Nicholas P. Lanzatella、Rozalin R. Dickson、Mary E. Messner、Huy H. Nguyen
DOI:10.1002/jhet.1571
日期:2013.7
Diels–Alder reactions of 5‐methylthio‐2‐vinyl‐1H‐pyrroles with maleimides followed by isomerization gave tetrahydroindoles in moderate to good yield. Aromatization using activated MnO2 in refluxing toluene gave the corresponding 2‐methylthioindoles in good yields, and demethylthioation using Raney nickel gave the 2‐H indoles in excellent yields. The protection of the adducts produced aromatization
5-甲硫基-2-乙烯基-1 H-吡咯与马来酰亚胺的Diels-Alder反应,然后异构化,得到中等产率至中等产率的四氢吲哚。使用活化的MnO 2进行芳香化在回流条件下,甲苯得到高收率的相应的2-甲基硫吲哚,用阮内镍进行脱甲基硫代反应得到的2-H吲哚的收率很高。加合物的保护以提高的收率产生芳构化,证明了甲硫基作为吡咯的保护基的有效性。但是,在Diels-Alder反应中,显示5-甲硫基-2-乙烯基吡咯的效率比2-乙烯基吡咯略低,表明该保护基的失活程度超过了预期。这种通往吲哚的途径提供了高度收敛性和易于获得的易于纯化的起始原料。已证明双甲硫基乙烯基吡咯具有作为高活化Diels-Alder二烯的潜力。