ChemCatChem
10.1002/cctc.201802079
COMMUNICATION
Scheme 5. Proposed Mechanism.
Acknowledgements
The authors gratefully acknowledge support from National
Natural Science Foundation of China (21502046), Natural
Science Foundation of Heilongjiang Province (B2016008) and
the University Nursing Program for Young Scholars with
Creative Talents in Heilongjiang Province (UNPYSCT-2017124).
The Fundamental Research Funds for the Central Universities
Scheme 3. Substrate Scope. (Isolated yields)
from
Harbin
Engineering
University
(HEUCFD1412,
HEUCFJ161002, HEUCFJ 171006, and HEUCFJ181008) were
also acknowledged. Dr. Guijie Mao was acknowledged for her
help in the NMR spectrum.
3
Keywords: PCET • Photoredox catalysis • C(sp )-H activation •
Alkenylation • Organocatalysis
Scheme 4. Radical Inhibition Experiments.
[
1]
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would generate adduct 6. The 7 promoted denitration of 6,
affording product 2 (Scheme 5).
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In summary, we successfully applied the readily available
nitroalkenes as the alkenylating reagents for C-H alkenylation of
ethers. The protocol allows the rapid access to the α-alkenyl
ethers with only E-isomers. The previous elusive α-dienyl ethers
are successfully gained as well. The mechanism study revealed
that alkenylation proceeded through a PCET process with a
3
denitration, which is responsible for selective C(sp )-H activation
of cyclic ethers and the good E/Z ratios. Further application of
this protocol to functionalization of ethers with other coupling
partners is under investigation in our lab.
1
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2
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Experimental Section
General experimental procedure (2a-2v): A mixture of nitroalkenes 1 (0.2
mmol, 1.0 equiv), 5,7,12,14-pentacenetetrone (PC V) (0.04 mmol, 20
mol%), and K CO (0.2 mmol, 1.0 equiv) in ether (10 mL) were irradiated
2 3
by two blue compact fluorescent lamp under Ar at rt for 36 h. The
solution was concentrated and purified by flash chromatography on silica
gel to give the pure 2a-2s.
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