10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
to elucidate the differences of NHSi ligands from phosphine
ligands are ongoing in our laboratories.
The bis-borylation of naphthalene and pyrene was also
examined (Table 2, 2u and 2v). These reactions led to the
isolation of the corresponding products in 77 and 78% yields,
respectively. The borylation of naphthalene yielded the 6- and 7-
borylated products in the molar ratio of 1:3, whereas borylation
of pyrene selectively gave the single product 2v.
Acknowledgements
HR, YPB and CC are grateful to the National Natural Science
Foundation of China (Grant No. 21390401 and 21472098) for
financial support. MD and YPZ thank the Deutsche
Forschungsgemeinschaft (Cluster of Excellence UniCat, ExIn
314/2) for support.
On the basis of the cobalt-catalyzed CH borylation
mechanism previously proposed[13] and our experiment results,
the tentative mechanism for the borylation reaction is outlined in
Scheme 5. It is reasoned that the cobalt(I) hydride A was
generated in situ upon addition of NaHBEt3 to precatalyst 1.
Unfortunately, many attempts to isolate and detect A were
unsuccessful date. The oxidative-addition of B2Pin2 to A could
lead to the intermediate B. Subsequently, the reductive
elimination of HBPin from B yielded the active cobalt (I) boryl
intermediate C. The CH oxidative-addition of an arene to C
followed by the reductive elimination of arylboronate ester
regenerated the cobalt (I) hydride A. In the presence of
cyclohexene, it reacted with the hydride A via coordinate-
insertion to form the intermediate E. Subsequent reductive
elimination yielded cyclohexane and C6H11BPin with the
generation of the cobalt boryl species C and hydride A,
respectively. In the absence of cyclohexene, with the increase of
the amounts of HBPin in the catalytic cycle the reductive
elimination of B to form C could be suppressed, thus the
catalytic cycle was interrupted.
Keywords: silylene • pincer ligand• cobalt • CH borylation •
silicon
References
[1]
Selected recent reviews: a) B. SSu, Z.–C. Cao, Z.–J. Shi, Acc. Chem.
Res. 2015, 48, 886; b) J. Wencel––Delord, F. Glorius, Nat. Chem. 2013,
5, 369; c) M. Miura, T. Satoh, K. HHirano, Bull. Chem. Soc. Jpn. 2014, 87,
751; d) J. Yamaguchi, A. D. Yamaaguchi, K. Itami, Angew. Chem. Int. Ed.
2012, 51, 8960; Angew. Chem. 20012, 124, 9092; e) T. W. Lyons, M. S.
Sanford, Chem. Rev. 2010, 110,, 1147; f) K. M. Engle, T.–S. Mei, M.
Wasa, J.–Q. Yu, Acc. Chem. Rees. 2012, 45, 788; g) F. Kakiuchi, T.
Kochi, S. Murai, Synlett 2014, 255, 2390; h) S. De Sarkar, W. Liu, S. I.
Ko-zhushkov, L. Ackermann, Advv. Synth. Catal. 2014, 356, 1461; i) G.
Rouquet, N. Chatani, Angew. Cheem. Int. Ed. 2013, 52, 11726; Angew.
Chem. 2013, 125, 11942.
[2]
[3]
[4]
a) I. A. I. Mkhalid, J. H. Barnardd, T. B. Marder, J. M. Murphy, J. F.
Hartwig, Chem. Rev. 2010, 110, 8890; b) J. F. Hartwig, Acc. Chem. Res.
2012, 45, 864.
a) D. G. Hall, Boronic Acids; Wileyy–VCH: Weinheim, Germany, 2005; b)
G. R. Dick, E. M. Woerly, M. D. Buurke, Angew. Chem. Int. Ed. 2012, 51,
2667; Angew. Chem. 2012, 124, 22721.
a) H. Chen, S. Schlecht, T. C. SSemple, J. F. Hartwig, Science 2000,
287, 1995; b) J.–Y. Cho, C. N. Ivverson, M. R. Smith, III. J. Am. Chem.
Soc. 2000, 122, 12868; (c) S. Kaawamorita, T. Miyazaki, H. Ohmiya, T.
Iwai, M. Sawamura, J. Am. Chem. Soc. 2011, 133, 19310; d) C. Cheng,
J. F. Hartwig, Science 2014, 343, 853.
[5]
[6]
a) T. Furukawa, M. Tobisu, N. Chhatani, J. Am. Chem. Soc. 2015, 137,
12211; b) J. Takaya, S. Ito, H. Noomoto, N. Saito, N. Kirai, N. Iwasawa,
Chem. Commun. 2015, 51, 176622.
a) M. A. Larsen, J. F. Hartwig, J. Am. Chem. Soc. 2014, 136, 4287; b)
S. M. Preshlock, B. Ghaffari, PP. E. Maligres, S. W. Krska, R. E.
Maleczka, M. R. Smith, III. J. Am. Chem. Soc. 2013, 135, 7572; c) G. A.
Chotana, M. A. Rak, M. R. Smitth, III. J. Am. Chem. Soc. 2005, 127,
10539; d) M. I. Gonzalez, E. D. Bloch, J. A. Mason, S. J. Teat, J. R.
Long, Inorg. Chem. 2015, 54, 29995; e) C. F. Rentzsch, E. Tosh, W. A.
Herrmann, F. E. Kühn, Green CChem. 2009, 11, 1610; f) Y. Saito, Y.
Segawa, K. Itami, J. Am. Chem. SSoc. 2015, 137, 5193; g) H. Tajuddin,
P. Harrisson, B. Bitterlich, J. C. CCollings, N. Sim, A. S. Batsanov, M. S.
Cheung, S. Kawamorita, A. C. Maaxwell, L. Shukla, J. Morris, Z. Lin, T.
B. Marder, P. G. Steel, Chem. Scii. 2012, 3, 3505.
Scheme 5. Proposed mechanism for [SiNSi]Cocatalyzed CH borylation of
arenes.
[7]
a) T. Hatanaka, Y. Ohki, K. Tatsuumi, Chem. Asian J. 2010, 5, 1657; b)
G. Yan, Y. Jiang, C. Kuang, S. Waang, H. Liu, Y. Zhang, J. Wang, Chem.
Commun. 2010, 46, 3170; c) T. DDombray, C. G. Werncke, S. Jiang, M.
Grellier, L. Vendier, S. Bontempss, J.–B. Sortais, S. Sabo–Etienne, C.
Darcel, J. Am. Chem. Soc. 2015, 137, 4062.
In summary, we reported the synthesis of the first bis(NHSi)
pyridine cobalt complex. This well-defined complex enabled the
facile and regioselective C–H borylation of fluorinated benzenes
in high yields. In particular, the observed distinct regioselectivity
from the known [PNP] cobalt catalyst suggested that NHSi
ligands can be complementary to phosphine ligands and thus
very promising for a wide scope of applications. Further studies
[8]
[9]
a) T. Furukawa, M. Tobisu, N. Chatani, Chem. Commun. 2015, 51,
6508; b) H. Zhang, S. Hagihara, KK. Itami, Chem. Lett. 2015, 44, 779.
T. J. Mazzacano, N. P. Mankad, JJ. Am. Chem. Soc. 2013, 135, 17258.
[10] a) G. Zhang, K. V. Vasudevan, B.. L. Scott, S. K. Hanson, J. Am. Chem.
Soc. 2013, 135, 8668; b) G. Zhanng, B. L. Scott, S. K. Hanson, Angew.
Chem. Int. Ed. 2012, 51, 12102; AAngew. Chem. 2012, 124, 12268.
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