Reactions of 2-lithiated indoles with elemental sulfur. Formation of pentathiepino[6,7-b]indoles and indoline-2-thiones

The reactions of 2-lithiated indole and 1-methylindole with elemental sulfu r have been studied, leading e.g. to a rational approach to pentathiepino[6 ,7-b]indoles 5 and 10. Notable amounts of the previously known tetrathiocin o[5,6-b:8,7-b ' ]diindole 11 could be observed as a side reaction in the pr eparation of 10. Treatment of the anions of indoline-2-thiones 6 or 7 with sulfur also gave the pentathiepins 5 or 10, respectively. In addition, a co nvenient and clean lithiation route to indoline-2-thione (6) has been devel oped. (C) 2001 Elsevier Science Ltd. All rights reserved.