Exploiting Hexafluoroisopropanol-Mediated Stereospecific Thiourea-Catalyzed <i>C</i> -Glycosylation of Indoles Enables Access to 2-Deoxy β- <i>C</i> -Indolyl Glycosides

Herein, we disclose a β-stereospecific indole <i>C</i>-glycosylation in HFIP by employing a (thio)urea catalyst, enabling facile access to 2-deoxy-β-<i>C</i>-indolyl glycosides. This reaction relies on the plausible formation of a catalyst-acceptor complex through noncovalent H-bond interactions between the N-H group of indole and the sulfur atom of the catalyst (N-H···S) and engaging π-π interactions between flanking aromatic substituents of indoles with catalyst, facilitating the glycosylation process under mild conditions. NMR analysis shows that hydrogen bonding between HFIP and glycal forms noncovalent interactions and control experiments combined with DFT calculations support the proposed mechanism.