156210-71-8Relevant articles and documents
Access to indoles via Diels-Alder reactions of 5-methylthio-2-vinylpyrroles with maleimides
Noland, Wayland E.,Lanzatella, Nicholas P.,Dickson, Rozalin R.,Messner, Mary E.,Nguyen, Huy H.
, p. 795 - 808 (2013/08/23)
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 in improved yield, demonstrating the effectiveness of the methylthio group as a protecting group for pyrroles; however, 5-methylthio-2-vinylpyrrole was shown to perform with slightly less efficiency than 2-vinylpyrrole in Diels-Alder reactions, indicating the protective group was more deactivating than desired. This route toward indoles offers high convergency and conveniently available starting materials that are easily purified. Bis-methylthioated vinylpyrroles were shown to have potential as highly activated Diels-Alder dienes.
