A photoinduced SET process enables the direct B−H bond activation of NHC–boranes. In contrast to common hydrogen atom transfer (HAT) strategies, this photoinduced reaction simply takes advantage of the beneficial redox potentials of NHC–boranes, thus obviating the need for extra radical initiators. The resulting NHC–boryl radical was used for the borylation of a wide range of α‐trifluoromethylalkenes and alkenes with diverse electronic and structural features, providing facile access to highly functionalized borylated molecules. Labeling and photoquenching experiments provide insight into the mechanism of this photoinduced SET pathway.
The
first photoredox-catalyzed defluoroborylation of polyfluoroarenes
with NHC-BH3 has been facilely achieved at room temperature
via a single-electron-transfer (SET)/radical addition pathway. This
new strategy makes full use of the advantage of photoredox catalysis
to generate the key boryl radical via direct activation of a B–H
bond. Good functional group tolerance and high regioselectivity offer
this protocol incomparable advantages in preparing a wide array of
valuable polyfluoroarylboron compounds. Moreover, both computational
and experimental studies were performed to illustrate the reaction
mechanism.
A photoinduced, phosphoranyl
radical-mediated protocol for the direct N–O cleavage of strained
cycloketone oximes via a polar/SET crossover process was developed
for the first time. This visible-light-driven direct N–O activation
mode for oxime offers beneficial features such as streamlined synthetic
process and versatile photochemical reactivities. Consequently, the
alkenes and α-trifluoromethyl alkenes with varied electronic
and structural features acted as competent radical receptors in this
protocol, enabling facile accesses to a range of elongated cyano and/or gem-difluoroalkene-bearing compounds.
A series of novel difluorinated 2‐hydroxyl‐substituted dihydroquinolones have been firstly synthesized via selectfluor‐triggered tandem cyclizations of 2‐aminoarylenaminones. This new approach could occur under mild reaction conditions, and features easy operation and scalability.
A practical and straightforward synthetic route to construct a variety of 3-CF/CF-containing chromones via photoredox catalysis was developed. This novel protocol features a visible-light-induced radical-triggered tandem cyclization.
A facile and diversified synthesis of functionalized CF-containing benzoxepine derivatives via photoredox catalysis was achieved in this work. This novel protocol features broad substrate scope, mild reaction conditions, operational simplicity, easy scale-up, and versatile derivatization, which would facilitate its practical and broad applications in the construction of valuable and synthetically challenging heterocycles.
O-Perfluoropyridin-4-yl
group was first installed
onto cycloketone oximes as a new electrophore, which was proven to
be efficient iminyl radical precursors under photocatalytic and thermal
conditions. A range of O-perfluoropyridin-4-yl oximes
were successfully utilized in C(sp2)–C(sp3) bond formations of quinoxalin-2(1H)-ones and alkenes,
providing facile accesses to a range of functionalized alkylnitriles.
A novel
visible-light-driven organocatalytic protocol to access
aerobic oxidative cleavage of olefins, promoted by sodium benzene
sulfinate, is described herein. An array of alkenes smoothly delivered
the corresponding aldehydes and ketones under transition-metal-free
conditions. Notably, α-halo-substituted styrenes proceeded with
photoinduced oxidation to finally afford α-halo-acetophenones
with halogen migration. Crucial to this oxidation was the formation
of charge-transfer complexes between sodium benzene sulfinate with
molecular O2 to ultimately deliver the carbonyl products.
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