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New Journal of Chemistry
Page 4 of 5
DOI: 10.1039/C6NJ03718F
COMMUNICATION
Journal Name
Based on these experiments and the literature,10,12,15,17 we have
proposed the possible mechanism for this palladium/copper-
catalyzed Heck-type coupling reaction (Fig. 1). N’-acyl arylhydrazine
(A) was oxidized by PdXY (X, Y = Cl, I, CF3COO) to give the diazene
intermediate B. The reductive Pd(0) coordinates with B to form the
azo-palladium complex (C), which undergoes a regioselective alkene
insertion under the acidic conditions with the release of R1Y, CO and
N2. Degeneration of the organopalladium intermediate D afforded a
coupling product E and regenerated the Pd(0) species, which may
be reoxidized to PdXY in the presence of air (Table 1, entry 1) or
under the mediation of the copper salt.
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Fig. 1 Proposed mechanism.
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Conclusions
In summary, with N’-acyl arylhydrazines as aryl donors, we
have developed
a novel, ligand-free and regioselective
palladium/copper catalyzed arylation of alkenes. This protocol,
using air as terminal oxidant, is simple, readily operated and
tolerates a broad substrate scope, which makes it quite
applicable in practical organic synthesis.
12 J.-Q. Zhang, G.-B. Huang, J. Weng, G. Lu and A. S. C. Chan, Org.
Biomol. Chem., 2015, 13, 2055-2063.
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84587-84591.
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2015, 44, 351-358.
15 Y.-G. Zhang, X.-L. Liu, Z.-Y. He, X.-M. Li, H.-J. Kang and S.-K. Tian,
Chem. - Eur. J., 2014, 20, 2765-2769.
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Experimental Section
A mixture of N’-acyl arylhydrazine 1 (0.3 mmol), alkene 2 (0.45
mmol), PdCl2 (0.015 mmol), CuI (0.03 mmol) and TFA (0.6 mmol) in
DMSO (2.0 mL) was stirred at 80 °C for 12-24 h. After completion of
the reaction (indicated by TLC), the mixture was quenched with
saturated NaCl solution and extracted with EtOAc, followed by
washing with H2O and saturated NaCl solution, and finally dried
over Na2SO4. The crude product was purified by flash column
chromatography to provide the corresponding product 3.
Acknowledgements
17 (a) D.-H. Wang, K. M. Engle, B.-F. Shi and J.-Q. Yu, Science, 2010,
327, 315-319; (b) R. F. Heck and J. P. Nolley, Jr., J. Org. Chem.,
1972, 37, 2320-2322; (c) F. Stieber, U. Grether and H. Waldmann,
Angew. Chem., Int. Ed., 1999, 38, 1073-1077; (d) D. Toummini, A.
Tlili, J. Berges, F. Ouazzani and M. Taillefer, Chem. - Eur. J., 2014,
20, 14619-14623.
This work was financially supported by National Science Fundation
of P. R. China (No. 81660573), National Science Grand Fundation of
Guizhou Province (No. JZ[2016]2001), Social Development of
Technical Supporting Fundation of Guizhou Province (No.
[2016]2819) and the Ph.D. Research Foundation of Guizhou Medical
University (No. J[2015]006).
Notes and references
1 (a) D. A. Colby, R. G. Bergman and J. A. Ellman, Chem. Rev., 2010,
110, 624-655; (b) S. R. Dubbaka and P. Vogel, Angew. Chem., Int.
Ed., 2005, 44, 7674-7684; (c) S. G. Modha, V. P. Mehta and E. V.
4 | J. Name., 2012, 00, 1-3
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