Regioselective Thiolation and Selenylation of Cyclic Diaryl λ ³ -Bromanes Enabled by Visible-Light Photocatalysis

Despite the broad utility of cyclic diaryl λ³-bromanes as aryne precursors for nucleophilic additions by heteroatom-based nucleophiles under mild basic conditions, their capacity to install arylchalcogen bonds in a regioselective manner is largely unexplored and challenging. The higher oxidative addition barrier of cyclic diaryl λ³-bromanes relative to their iodine analogues leads to transition-metal-catalyzed aryl-chalcogen bond formation requiring more forcing conditions, which decreases the regioselectivity. Moreover, the oxidizing character of hypervalent bromanes might be problematic. Herein, we disclose a photocatalytic strategy to achieve highly regioselective thiolation and selenylation of cyclic diaryl λ³-bromanes. This reaction proceeds under mild reaction conditions and exhibits a broad substrate scope with a good functional group tolerance and excellent regioselectivity.