Journal of the American Chemical Society
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(6) For examples of ironꢀcatalyzed monoꢀcarbometalation and hyꢀ
nature of the NHC ligand in combination with its appropriate
steric property of IEt2Me2 should be the key contributing
factors.15 Benefited from these features, the ligand displacement
of IEt2Me2 by carboanions or an alkyne molecule might be hard to
occur on the organoiron intermediates AꢀC, thereby depressing
the side reaction of uncontrolled multiꢀcarbometalation to form
oligomers or polymers.4 On the other hand, the appropriate steric
property of IEt2Me2 could allow the iron alkenyl species B to
drometalation reactions, please see ref. 5 and (a) Fürstner, A.;
Méndez, M. Angew. Chem., Int. Ed. 2003, 42, 5355ꢀ5357. (b)
Shirakawa, E.; Yamagami, T.; Kimura, T.; Yamaguchi, S.;
Hayashi, T. J. Am. Chem. Soc. 2005, 127, 17164ꢀ17165. (c)
Zhang, D.; Ready, J. M. J. Am. Chem. Soc. 2006, 128, 15050ꢀ
15051. (d) Lu, Z.; Chai, G.; Ma, S. J. Am. Chem. Soc. 2007, 129,
14546ꢀ14547. (e) Shirakawa, E.; Ikeda, D.; Ozawa, T.;
Watanabe, S.; Hayashi, T. Chem. Commun. 2009, 1885ꢀ1887. (f)
Ilies, L.; Yoshida, T.; Nakamura, E. J. Am. Chem. Soc. 2012,
134, 16951ꢀ16954. (g) Hata, T.; Iwata, S.; Seto, S.; Urabe, H.
Adv. Synth. Catal. 2012, 354, 1885ꢀ1889.
1
2
3
4
5
6
7
8
react with
a
molecule of alkyne, leading to doubleꢀ
carbometalation, but render the further reaction of the iron dienyl
species C with alkyne difficult due to steric repulsion between the
NHC ligand and the highly substituted 1,3ꢀdienyl group. The
molecular structures of 5 and 15 clearly indicate the highly
substituted dienes have nonꢀplanar 1,3ꢀdiene cores and are steric
demanding.
9
(7) For characterization data, please see supporting information.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(8) For selected examples of transitionꢀmetalꢀcatalyzed or
–
mediated transformations of alkynes to conjugated dienes and
polyenes, please see: (a) van Belzen, R.; Hoffmann, H.; Elsevier,
C. J. Angew. Chem., Int. Ed. 1997, 36, 1743ꢀ1745. (b) Satoh, T.;
Ogino, S.; Miura, M.; Nomura, M. Angew. Chem., Int. Ed. 2004,
43, 5063ꢀ5065. (c) Wu, T.ꢀC.; Chen, J.ꢀJ.; Wu, Y.ꢀT. Org. Lett.
2011, 13, 4794–4797. (d) Takahashi, T.; Liu, Y.; Iesato, A.;
Chaki, S.; Nakajima, K.; Kanno, K.ꢀI. J. Am. Chem. Soc. 2005,
127, 11928ꢀ11929. (e) Kanno, K.ꢀI.; Igarashi, E.; Zhou, L.;
Nakajima, K.; Takahashi, T. J. Am. Chem. Soc. 2008, 130,
5624ꢀ5625. (f) Wei, J.; Wang, Z.; Zhang, W.ꢀX.; Xi, Z. Org.
Lett. 2013, 15, 1222–1225. (g) Geng, W.; Wei, J.; Zhang, W.ꢀX.;
Xi, Z. J. Am. Chem. Soc. 2014, 136, 610ꢀ613.
In summary, we found that iron(II)ꢀNHC complexes can serve
as catalysts for the doubleꢀcarbometalation reactions of
unsymmetrical internal alkynes with alkyl Grignard reagents. The
high regioꢀ and stereoselectivity of the ironꢀcatalyzed reaction
enables the selective synthesis of highly substituted 1,3ꢀdienyl
magnesium reagents. The achievement of the doubleꢀ
carbometalation reaction demonstrates the feasibility of
controlling the degree of multiꢀcarbometalation of alkynes upon
judicious selection of catalysts. Inspired by this, we are now
pursuing ironꢀcatalyzed controlled tripleꢀcarbometalation reaction
for the production of 1,3,5ꢀtrienyl metal reagents.
(9) (a) Yoshikai, N.; Mieczkowski, A.; Matsumoto, A.; Ilies, L.;
Nakamura, E. J. Am. Chem. Soc. 2010, 132, 5568ꢀ5569. (b)
Czaplik, W. M.; Grupe, S.; Mayer, M.; Jacobi von Wangelin, A.
Chem. Commun. 2010, 6350ꢀ6352.
(10) Ghorai, S. K.; Jin, M.; Hatakeyama, T.; Nakamura, M. Org. Lett.
2012, 14, 1066–1069.
(11) The Nꢀethyl NHC ligand is incapable of stabilizing iron(II) pheꢀ
nyl and ethyl species, see: Xiang, L.; Xiao, J.; Deng, L. Organꢀ
ometallics 2011, 30, 2018–2025.
(12) (a) Smith, J. M.; Lachicotte, R. J.; Holland, P. L. J. Am. Chem.
Soc. 2003, 125, 15752ꢀ15753. (b) Yu, Y.; Sadique, A. R.; Smith,
J. M.; Dugan, T. R.; Cowley, R. E.; Brennessel, W. W.;
Flaschenriem, C. J.; Bill, E.; Cundari, T. R.; Holland, P. L. J.
Am. Chem. Soc. 2008, 130, 6624ꢀ6638.
(13) Liu, Y.; Wang, L.; Deng, L. Organometallics 2015, 34, 4401ꢀ
4407.
(14) (a) Huggins, J. M.; Bergman, R. G. J. Am. Chem. Soc. 1979,
101, 4410ꢀ4412. (b) Huggins, J. M.; Bergman, R. G. J. Am.
Chem. Soc. 1981, 103, 3002ꢀ3011.
(15) (a) Lavallo, V.; Canac, Y.; Präsang, C.; Donnadieu, B.; Berꢀ
trand, G. Angew. Chem., Int. Ed. 2005, 44, 5705ꢀ5709. (b) Hahn,
F. E.; Jahnke, M. C. Angew. Chem., Int. Ed. 2008, 47, 3122ꢀ
3172.
ASSOCIATED CONTENT
Supporting Information. The Supporting Information is availaꢀ
ble free of charge on the ACS Publications website at DOI:
xxxxxxxxx.
Experimental procedures, characterization data, NMR, and GC
spectra (PDF)
Crystallographic data (CIF)
AUTHOR INFORMATION
Corresponding Author
* Eꢀmail: deng@sioc.ac.cn
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
We thank the financial support from the National Natural Science
Foundation of China (Nos. 21121062 and 21432001).
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