Visible-light-mediated chemical reactions have become highly popular in the last ten years. This review covers the recent developments in visible-light photofunctionalization of quinoxalin-2-one derivatives. Reaction types have been categorized depending on the kind of bond formed: CC , CO , [a
An enantioselective photooxidative Mannich reaction of dihydroquinoxalinones with ketones by the merger of organophotoredox and asymmetric organocatalysis is described. This protocol features a very mild reaction conditions using simple and cheap catalysts (Eosin Y and (S)-Proline) for the synthesis of chiral quinoxaline derivatives with good to high yields (up to 94%) and excellent enantioselectivities (up to 99% ee).
The asymmetric Mannich reaction is one of the most straightforward methodologies for the enantioselective synthesis of chiral amines. In general, asymmetric Mannich reactions involve the use of imines as electrophiles. However, in recent years, several asymmetric oxidative Mannich reactions have been reported using amines as electrophiles. This review provides an overview of these recent publications, including the different oxidants used and the scope and limitations of the different catalytic systems.
The
visible-light photoredox-catalyzed coupling of 1,4-dihydroquinoxalin-2-ones
and Michael acceptors was achieved using Ru(bpy)3Cl2 as the photocatalyst and (PhO)2PO2H
as an additive. The optimized reaction conditions provide a good yield
for the radical conjugate addition products (44 examples) with a wide
range of structurally different Michael acceptors. A gram scale reaction
using sunlight irradiation is also described. Furthermore, several
transformations were carried out with the Giese addition products.
A visible-light photocatalytic
radical addition reaction of dihydroquinoxalin-2-ones
to trifluoromethyl ketones has been established using Ru(bpy)
3
Cl
2
as photocatalyst, acetonitrile as solvent,
and HP Single Blue LED as the source of light. The reaction provides
a straightforward approach to the synthesis of dihydroquinoxalin-2-ones
bearing a trifluoromethyl-substituted tertiary alcohol moiety in moderate
to good yields under mild conditions.
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