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.
Functionalization of ethylene without polymerization is challenging under photoirradiation conditions. We have demonstrated that the photo-transformation of ethylene can be controllable by merging photoredox and transition-metal catalysis. In our study, the use of different photoredox catalysts was able to modulate the oxidation state of the nickel catalyst. Through different oxidation states, the nickel-catalyzed couplings proceeded via distinct pathways to generate divergent ethylene difunctionalization products selectively from the same feedstock.
Visible‐light‐mediated regioselective allylation, benzylation, and silylation of methylene‐malononitriles using allylic/benzylic silane and disilane reagents have been developed, delivering the corresponding allylated, benzylated, and silylated products in moderate to excellent yields. These reactions proceed smoothly with exclusive regioselectivity by employing only an organo‐photoredox catalyst under very mild conditions. A photoredox‐induced radical cation fragmentation is proposed for the generation of the key allylic, benzylic, and silyl radicals.
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