Angewandte Chemie International Edition
10.1002/anie.202008261
RESEARCH ARTICLE
the opposite effect. Preliminary mechanistic research revealed
the reaction sequence in a tandem manner. This work not only
exhibits the ability to successive cleavage adjacent -(C-C)n-
bonds but also provides a new practical method for directly
accessible ester through C-C bond cleavage in alcohols, which
is still challenging to the existing methods.
Acknowledgements
Financial support from the National Natural Science Foundation
of China (No. 21773227, 21773232, and 21902151).
Keywords: C-C bond • aerobic oxidative cleavage • alcohols •
heterogeneous cobalt catalyst • esters
Scheme 8. Proposed mechanism of the oxidative cleavage C-C bonds of
secondary alcohols to ester over the Co-NC-900 catalyst.
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7
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According to the above results and our previous work, we can
provide
a plausible reaction mechanism of the oxidative
2
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catalyst (Scheme 8). Initially, the substrate is oxidized to 7a
through the reactive oxygen species produced by activation of
oxygen by cobalt nanoparticles.[24] Subsequent aerobic oxidation
of 7a generates 7b which is further oxidized to 7c. Then, there
are two possible reaction pathways. On one hand, the generated
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c is oxidized to 7d, and then the cleavage of C-C bond affords
9
the ester 2o with release of formic acid followed by the
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2 2
decomposing to CO and H (Supporting Information, Figure S17
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and 18).[
11a, 25]
On the other hand, 7c reacts with water to form
the hydrated a,a-bis(hydroxy)acetophenone (7e). C-C bond
cleavage occurs via 1,2-hydride shift, generating 7g and CO
2
.
[
[
[
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to form the hemiacetal intermediate. Finally, the hemiacetal
intermediate is transformed to 2o catalyzed by the Co/O system.
2
The similar reaction pathway of Co-catalyzed adjacent -(C-C)n-
bond cleavage of primary alcohols is verified by some control
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In summary, we have successfully prepared heterogeneous Co-
NC catalysts for the aerobic oxidative successive C-C bond
cleavage of various functionality aromatic, aliphatic, heterocyclic,
allylic, propargylic primary and secondary alcohols to one or
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2
multiple carbon atoms shorter esters with O as the oxidant. The
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catalyst was used for seven times without any decrease in
activity. Catalyst characterization and control experiments
demonstrated that cobalt nanoparticles are responsible for
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x
excellent catalytic activity, while the presence of Co-N has just
6
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