Alkoxy
radicals are highly reactive species that have long been
recognized as versatile intermediates in organic synthesis. However,
their development has long been impeded due to a lack of convenient
methods for their generation. Thanks to advances in photoredox catalysis,
enabling facile access to alkoxy radicals from bench-stable precursors
and free alcohols under mild conditions, research interest in this
field has been renewed. This review comprehensively summarizes the
recent progress in alkoxy radical-mediated transformations under visible
light irradiation. Elementary steps for alkoxy radical generation
from either radical precursors or free alcohols are central to reaction
development; thus, each section is categorized and discussed accordingly.
Throughout this review, we have focused on the different mechanisms
of alkoxy radical generation as well as their impact on synthetic
utilizations. Notably, the catalytic generation of alkoxy radicals
from abundant alcohols is still in the early stage, providing intriguing
opportunities to exploit alkoxy radicals for diverse synthetic paradigms.
CuH-catalyzed diasterospecific
synthesis of 3-hydroxyindolines
and 2-aryl-3H-indol-3-ones have been developed from o-alkynylnitroarenes in the presence of hydrosilane as the reductant.
The protocol employs nitro as both nitrogen and oxygen sources for
the intramolecular simultaneous construction of C–N and C–O
bonds.
A CuH-catalyzed Z-selective partial reduction of alkynyl amides to afford α,β-unsaturated amides using silane as the hydrogen donor is developed. A broad scope of alkynyl amides is accommodated, affording alkenyl amides with high stereoselectivity and excellent yields.
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