Regioselective intramolecular cyclization of o-alkynyl arylamines with the in situ formation of ArXCl to construct poly-functionalized 3-selenylindoles

Abstract

In this paper, we have developed a metal-free protocol for the controllable synthesis of various 3-selenyl/sulfenyl/telluriumindoles from the regioselective intramolecular cyclization reactions of in situ generated RXCl with o-alkynyl arylamines.

PIFA/Ar2Te2‐Mediated Synthesis of 3‐Aryltelluroindoles via Intramolecular Cyclization of 2‐Alkynylanilines

“…As 3-sulfenylindoles and 3-selenylindoles could be oxidized into their corresponding sulfoxide/sulfone and selenoxide/ selenone compounds by reacting with mCPBA in different ratios, [26,37] mCPBA-mediated oxidation, [38] we treated 2 a with 1 equiv. and 2 equiv.…”

“…However, only one single example was studied, possibly due to the non-readily accessibility of diarylditellurides. [26] In this work, we reported that synthesis of the highly substituted 3-aryltelluroindoles could be accomplished through intramolecular cyclization and tellurolation of 2-alkynylanilines mediated by PIFA, an alternative hypervalent iodine reagent and various diaryl ditellurides (ArTeTeAr).…”

“…Most recently, Zhang and co‐workers realized the synthesis of 3‐aryltelluroindole from 2‐alkynylanilines via the intramolecular cyclization enabled by the reactive PhTeCl species, in situ formed from the reaction of diphenylditelluride and PhICl 2 . However, only one single example was studied, possibly due to the non‐readily accessibility of diarylditellurides [26] . In this work, we reported that synthesis of the highly substituted 3‐aryltelluroindoles could be accomplished through intramolecular cyclization and tellurolation of 2‐alkynylanilines mediated by PIFA, an alternative hypervalent iodine reagent and various diaryl ditellurides (ArTeTeAr).…”

Electrochemical selenocyclization of 2-ethynylanilines with diselenides: facile and efficient access to 3-selenylindoles

“…4 Apart from introducing selenium-containing substituents into already established indole scaffolds via direct C–H selenation, 5 selenocyclization of 2-ethynylanilines which simultaneously constructs the indole skeleton is another versatile path to access 3-selenylindoles. 6–9 For selenium-containing precursors, diselenide (RSeSeR) represents a user-friendly choice with higher stability and lower toxicity when compared to other corrosive reagents such as selenyl halides. 10…”

“…So far, several approaches for the selenocyclization of 2-ethynylanilines with diselenides have been established under thermal conditions, with the application of stoichiometric chemical oxidants, transition metal catalysts, strong bases, etc ., as the promoters (Scheme 1a). 6,7 Certain drawbacks, including potential safety risk, high cost, low atom economy, by-product pollution, long reaction time and harsh conditions limit their application to some extent. In 2017, a metal-free, visible light-induced photoredox selenocyclization was disclosed by the groups of Li and Wang, by employing hydrogen peroxide as a green oxidant via a radical pathway (Scheme 1b).…”