Metal-free CH-CH-type couplings of Dibenzothiophene S-oxides and Phenols

Abstract

Preliminary investigations by our group have highlighted that the sequential activation of benzothiophene sulfoxides with trifluoroacetic anhydride (TFAA) at low temperatures, and its exposure to phenol drives, upon reaching room temperature, the formation of C4-arylated benzothiophenes in 40-70% yield. Building on these findings, my investigation involved extending the method to achieve the arylation of dibenzothiophenes. Herein, a new and efficient method for the C1-selective arylation of dibenzothiophenes via metal free CH-CH-type couplings with phenols is described. The arylation reaction uses trifluoroacetic anhydride (TFAA), trifluoroacetic acid (TFA) and commercially available phenols to afford C1-functionalised dibenzothiophene products without the need to use expensive, supply-risk, transition metal catalysis and organometallic reagents. Notably, to our knowledge this represents the first metal-free method for the C1-selective arylation of dibenzothiophenes. The products can easily be obtained at room temperature and in short reaction times. Overall, this sequential approach offers unprecedented, mild, and general access to C1-arylated dibenzothiophenes, for which very few synthetic options are currently available, and rapid access to medicinally relevant sulfur-containing heterocyclic compounds.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Procter (Supervisor) & Michael Turner (Supervisor)