DOI: 10.1039/C6OB00730A
Organic & Biomolecular Chemistry
azaindole 1a and coordination of nitrogen by rhodium forms a
rhodacycle I. Subsequent isopropenyl acetate 2a coordinates to
rhodacycle I to give intermediate II. Regioselective insertion of
alkene into the Rh-C bond generates a rhodacyclic intermediate
III, which then undergoes nitrogen decoordination and roll-over
C−H activation to form the key intermediate IV (or isomer IV’)
followed by reductive elimination and C-O bond oxidative
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4
4
5
5
6
6
7
7
8
0
5
0
5
0
5
0
5
0
5
0
5
2
3
9
b
addition yield intermediate VI. Finally, the intermediate VI
undergoes β-Hydride elimination process to release the final
product 3aa and a rhodium hydride species. The resulting H-Rh
species reacts with isopropenyl acetate 2a yielding alkyl rhodium
species followed by protonolysis of Rh-C bond with HOAc to
regenerate the [Cp*Rh(III)] species and liberate alkyl acetate
1
(
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1
4
2
1
0
(
which has been detected by LCMS). Base was crucial in the
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1
catalytic system not only to prevent undiresd simple alkenylation
process but also to accelerate the second C−H activation process.
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HOAc
1
a
O
Cp*RhIII
r
-
Fi
st C H
5
6
7
8
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Chen, Org. Lett., 2013, 15, 1878.
[
]
O
H+
a
RhIIICp* OAc
2
( )
O
O
N
N
O
aa
β-H Elim.
H-RhIIICp*(OAc)
RhIII
3
O
2a
*
Cp
I
(a) N. Umeda, K. Hirano, T. Satoh, N. Shibata, H. Sato, M. Miura, J.
Org. Chem., 2011, 76, 13; (b) Z. Qi, S. Yu, X. Li, J. Org. Chem.,
Cp*
RhIII(OAc)
2
015, 80, 3471; (c) X. Liu, X. Li, H. Liu, Q. Guo, J. Lan, R. Wang, J.
N
N
You, Org. Lett., 2015, 17, 2936; (d) S.-S. Li, C.-Q. Wang, H. Lin, X.-
M. Zhang, L. Dong, Org. Lett., 2015, 17, 3018.
H
N
N
AcO
RhIII
*
Cp
RhIII
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Chem., 2015, 80, 620; (b) N. J. Webb, S. P. Marsden, S. A. Raw, Org.
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VI
Cp*
Ox. Add.
N
O
N
II
O
O
alkene
i
nsertion
N
O
N
N
N
RhI
IV'
+
*Cp RhIII
H
Cp*
*
Cp
RhIII
O
O
O
V
N
O
III
R.E.
N
H+
H
roll-over
Second C-H
IV
2
016, 14, 229.
9
For selected examples using an internal oxidant, see: (a) B. Liu, C.
Song, S. Zhou, J. Zhu, J. Am. Chem. Soc., 2013, 135, 16625; (b) N.
Guimond, S. I. Gorelsky, K. Fagnou, J. Am. Chem. Soc., 2011, 133,
Scheme 5 Plausible reaction mechanism.
6
(
1
449; (c) T. K. Hyster, T. Rovis, Chem. Commun., 2011, 47, 11846;
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6, 1684; (e) S. Rakshit, F. W. Patureau, F. Glorius, J. Am. Chem.
Conclusion
2
0
In summary, we have firstly developed the highly efficient
rhodium(III)-catalyzed N-directed ortho C−H activation and
subsequent roll-over C−H activation using electron-donating
olefins as the coupling partners to form a range of π-conjugated
85
Soc., 2010, 132, 9585.
1
1
0
1
For more details, see the Supporting Information.
(a) L. Liang, Q. Liu, J. Zhang, F. Wang, Y. Yuan, Res Chem
Intermed, 2013, 39, 1957; (b) L. Liao, C. Shu, M. Zhang, Y. Liao, X.
Hu, Y. Zhang, Z. Wu, W. Yuan, X. Zhang, Angew. Chem. Int. Ed.,
2014, 53, 10471.
7
-azaindole derivatives. The keys of this annulation reaction to
90
2
5
success were the application of base. We anticipate that the
approach will find broader applications in the formation of fused
polycyclic heterocyclic frameworks and useful products.
Acknowledgments
We are grateful for the financial support from the NSFC
(21582138).
3
0
Notes and references
1
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2
392; (b) S. S. Palayangoda, X. Cai, R. M. Adhikari, D. C. Neckers,
3
5
Org. Lett., 2008, 10, 281; (c) A. Facchetti, Chem. Mater., 2011, 23,
4
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