A Radical Smiles Rearrangement Promoted by Neutral Eosin Y as a Direct Hydrogen Atom Transfer Photocatalyst

A visible-light-mediated
radical Smiles rearrangement has been
achieved using neutral eosin Y as a direct hydrogen atom transfer
(HAT) photocatalyst. Novel N-heterocycles as single
diastereomers featuring an isothiazolidin-3-one 1,1-dioxide moiety
are directly accessed by this method. A wide range of functional groups
can be incorporated in the products by employing diverse aldehydes
and N-(hetero)­arylsulfonyl propiolamides. The transformation
proceeds through a cascade of visible-light-induced HAT, 1,4-addition,
Smiles rearrangement, 5-endo-trig cyclization, and
a reverse HAT process. Preliminary biological studies of the highly
functionalized heterocyclic compounds suggest potential anticancer
activity with some of the synthesized compounds.