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COMMUNICATION
Journal Name
intermediate was involved.13 The alkenylation product formed
from the reaction of deuterated benzamide with 2 further
supports this mechanism.
DOI: 10.1039/C9CC08735D
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Taken together, the following mechanism was proposed
(Scheme 4). Directed C-H cleavage affords an iridacycle 12.
Insertion of an alkyne into the iridium hydride generates a vinyl
iridium species 13, which undergoes reaction with a terminal
alkyne to form an iridium acetylide 14. Finally, reductive
elimination delivers the alkynylation product and regenerates
the catalyst. Alternatively, the iridacycle 12 interacts with
terminal alkyne to form a vinylidene species 15. Migratory
insertion of the vinylidene followed by reductive elimination
generates the alkenylation product.
NHMe
NHMe
O
4a 1a
1a 3a
NHMe
O
O
Ir
P
P
Ir
Ir
P
P
H
H
11
16
P
14
P
TIPS
TIPS
TIPS
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NHMe
2
NHMe
O
NHMe
O
O
P
Ir
H
Ir
Ir
P
P
P
H
P
2
P
2
15
H
TIPS
12
TIPS
13
Scheme 4. Proposed mechanism.
In summary, we have developed an iridium-catalyzed, ligand-
controlled reaction of arenes with terminal alkynes. Both C-H
alkynylation and alkenylation products were obtained in high
selectivity by simple choice of the ligand. The C-H alkynylation
proceeds without any external oxidant, while the C-H alkenylation
occurs through an unusual vinylidene mechanism. Further
improvement of the reaction efficiency and elucidation of the
reaction mechanism are currently ongoing in our laboratory.
This work was supported by the National Natural Science
Foundation of China (Grant No. 21672122 and No. 91856107).
Conflicts of interest
There are no conflicts to declare.
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Notes and references
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