Angewandte
Chemie
À
C H Activation
German Edition:
À
Cobalt(III)-Catalyzed Aryl and Alkenyl C H Aminocarbonylation
with Isocyanates and Acyl Azides**
Jie Li and Lutz Ackermann*
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Abstract: Expedient C H aminocarbonylations of unactivated
(hetero)arenes and alkenes were accomplished with a cobalt-
(III) catalyst that shows high functional group tolerance. The
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C H functionalization occurred with excellent chemo-, site-,
and diastereoselectivity and enabled step-economical reactions
with isocyanates or acyl azides.
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Figure 1. Cobalt-catalyzed C H aminocarbonylation.
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T
ransition-metal-catalyzed C H functionalization reactions
have emerged as increasingly powerful tools for the sustain-
able synthesis of organic compounds.[1] Considerable progress
in the assembly of aromatic amides was recently realized
through C H functionalization by isocyanates, with key
We commenced our studies by exploring reactions con-
ditions for the envisioned cobalt-catalyzed aminocarbonyla-
tion of pyrazolylbenzene (1a) with isocyanate 2a (Table 1 and
Table S1 in the Supporting Information). The nature of the
additive appeared to be critical and the combination of
AgOPiv with either AgSbF6 or AgNTf2 gave optimal results
(entries 1–11). The molecular complex [Cp*CoI2(CO)][14] in
particular was highly effective (entry 11) and test reactions
verified the crucial importance of the cobalt catalyst and the
additives (entries 12 and 13). In contrast, simple cobalt salts
failed to give the desired benzamide 3aa (entries 14–16).
With the optimized cobalt catalyst in hand, we tested the
scope of the reaction with a representative set of decorated
[2]
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contributions from the groups of Kuninobu/Takai, Bergman/
Ellman, Cheng, Li, and Ackermann, among others.[3] Despite
À
these major advances, all catalyzed C H activations with
isocyanates have thus far been accomplished with complexes
of the expensive 4d or 5d transition metals rhenium, rhodium,
or ruthenium. In consideration of the cost-effective nature of
first-row transition metals, recent focus has shifted towards
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the use of catalysts based on abundant base metals for C H
functionalization.[4] In this context, Nakamura, Yoshikai, and
Ackermann recently utilized low-valent cobalt catalysts for
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C H transformations that were until then the domain of
precious rhodium, palladium, and ruthenium catalysts.[5,6]
Furthermore, high-valent cobalt(III) catalysts were very
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Table 1: Optimization of cobalt(III)-catalyzed C H aminocarbonyla-
tion.[a]
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recently employed for chemoselective C H functionalization
as reported by the groups of Matsunaga/Kanai,[7] Acker-
mann,[8] Glorius,[9] Ellman,[10] and Chang.[11,12] As part of our
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research program on base-metal-catalyzed C H functionali-
zation,[13] we have developed a cobalt-catalyzed C H func-
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tionalization with isocyanates as the electrophiles that
provides expedient access to substituted benzamides under
mild reaction conditions (Figure 1). Notable features of our
strategy include 1) the use of user-friendly cobalt catalysts,
Entry
[Co]
Additive 1
Additive 2
Yield [%][c]
1
2
3
4
5
6
7
8
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
[Cp*CoI2(CO)]
–
AgPF6
AgPF6
AgPF6
AgNTf2
AgPF6
AgPF6
AgPF6
AgSbF6
AgNTf2
AgPF6
AgSbF6
AgPF6
AgPF6
AgSbF6
AgSbF6
AgSbF6
CsOAc
KOPiv
NaOPiv
AgOAc
AgOAc
KOAc
AgOPiv
AgOPiv
AgOPiv
AgOPiv
AgOPiv
–
–
–
–
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2) the versatile C H aminocarbonylation of arenes, hetero-
arenes, and alkenes with ample substrate scope, and 3) expe-
dient amide syntheses that proved viable with isocyanates or
azides.
35
23
24
42
46
57
64[b]
67[b]
–
–
–
–
–
[*] J. Li, Prof. Dr. L. Ackermann
9
Institut fꢀr Organische und Biomolekulare Chemie
Georg-August-Universitꢁt Gçttingen
Tammannstraße 2, 37077 Gçttingen (Germany)
E-mail: Lutz.Ackermann@chemie.uni-goettingen.de
10
11
12
13
14
15
16
AgOPiv
AgOPiv
AgOPiv
AgOPiv
CoI2
Co(OAc)2
[Co(acac)2]
[**] Generous support by the European Research Council under the
European Community’s Seventh Framework Program (FP7 2007–
2013)/ERC Grant agreement no. 307535, and the Chinese Scholar-
ship Program (fellowship to J.L.) is gratefully acknowledged.
[a] General reaction conditions: 1a (0.5 mmol), 2a (1.0 mmol), [Co]
(2.5 mol%), DCE (2.0 mL), 708C, 16 h. [b] [Cp*CoI2(CO)] (5.0 mol%),
additives (10 mol%). [c] Yield of isolated product. Piv=pivalate.
Supporting information for this article is available on the WWW
Angew. Chem. Int. Ed. 2015, 54, 1 – 5
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
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