XtalFluor‐E effects the C3‐H sulfenylation of indoles to form di‐indole sulfides

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A simple, regioselective synthesis of di-indole sulfides by electrophilic aromatic substitution of the C3-position of indoles was achieved using Xtalfluor-E as the sulfenylating reagent. The addition of amine bases was found to have a significant effect on the reaction outcome, with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) switching off the reactivity of XtalFluor-E, while the hindered base 2,6-ditertbutyl-4-methylpyridine (DBP) led to the formation of two di-indole-sulfur containing products, one S(II) and one S(IV). The optimal base for accessing the di-indole sulfides in high yield proved to be Hünigs base, EtNi Pr2 . While this amine formed a Lewis adduct with XtalFluor-E, adduct formation did not completely quench electrophilic reactivity indicating reversible coordination to the sulfur centre. This is the first report utilising XtalFluor-E in electrophilic aromatic substitution to form C-S bonds to our knowledge, and this process is applicable to a wide range of functionalised indoles and does not require N1-protection.
Original languageEnglish
JournalEuropean Journal of Organic Chemistry
Early online date11 Feb 2022
Publication statusE-pub ahead of print - 11 Feb 2022


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