Visible-Light-Driven Tandem Cyclization of o-Hydroxyaryl Enaminones: Access to 3-(α-Arylsulfonamido)trifluoroethyl Chromones

A visible-light-driven intermolecular tandem α-amidotrifluoroethylation/cyclization of enaminones using a previously unreported N-trifluoroethylaminopyridinium salt was achieved in the absence of transition metal catalysts or bases. Notable features of this synthetic method include mild conditions, high selectivity, excellent functional group compatibility, and satisfactory yields. Preliminary mechanistic studies indicate that the reaction proceeds via a radical pathway, involving an in situ generated N-trifluoroethyl radical, followed by a 1,2-H shift.