1.
J Org Chem
; 86(17): 11698-11707, 2021 09 03.
Article
in English
| MEDLINE
| ID: mdl-34338514
ABSTRACT
A new approach for the annulation of a thiopyrane ring to an indole core under mild conditions was developed. Treating 2-methyl-3-acylindoles with lithium diisopropyl amide leads to the elimination of a proton from the 2-methyl group. The lithium indole-2,3-dienolates obtained were found to react with CS2 to give the corresponding thiopyrano[4,3-b]indole-3(5H)-thiones. The mechanism represents a stepwise addition through ion-pair formation, according to PCM/B3LYP/6-311++G**, PBE1PBE/6-311++G**, and MP2//HF/6-311++G** quantum chemical calculations. AIM calculations revealed the essential role of the Li atom at all stages of the process.