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Chem Commun
ChemComm
DOI: 10.1039/C5CC04111B
a
Institute of Next Generation Matter Transformation, College of
Chemical Engineering at Huaqiao University, 668 Jimei Blvd, Xiamen,
Fujian, 361021, P. R. China. Eꢀmail: qsong@hqu.edu.cn
Financial support from the National Natural Science Foundation of
China (21202049), the Recruitment Program of Global Experts (1000
Talents Plan), Fujian Hundred Talents Program and Program of
Innovative Research Team of Huaqiao University (Z14X0047) are
gratefully acknowledged. The authors also thank Miss Huibing Huang for
her work on experiments.
Scheme 3 Large scale experiment
Based on the above studies and discussions on palladium
complexes containing NꢀN multiple bonds in previous reports,11
and the detailed study on the reaction of PdII complex with
phenylhydrazine (1a) carried out by Loh et al.,6e a general
mechanism is illustrated in Scheme 4. Initially, ligand exchange
of the PdII precursor by phenylhydrazine affords the
†
Electronic Supplementary Information (ESI) available: [Experimental
details and full spectroscopic data for all products]. See
DOI: 10.1039/c000000x/
palladadiaziridine (I), which allows the oxidative addition with
Pd0 to afford the two PdIIꢀcentered complex II. Protonolysis of
II releases the arylpalladium complex III and the
palladiaziridine complex IV, which collapses to give Pd0,
nitrogen gas, and water in the presence of oxygen. The reaction
of palladium complex III with terminal alkyne 2a might
1
(a) L. Cassar, J. Organomet. Chem., 1975, 93, 253ꢀ257; (b) H. A.
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experience
a
typical complexationꢀdehydropalladationꢀ
reductive elimination to afford the product 3aa. The anionic
ligand X (OAc) might play the role of internal base.12 However,
a carbopalladationꢀβꢀhydride elimination step is also feasible,
which could be found in many baseꢀfree cases.13 Finally, the
catalytic cycle is closed upon reoxidation of Pd0 to PdII by
oxygen with the assistance of acetic acid.
,
874ꢀ922; (f) R. Chinchilla and C. Najera, Chem. Soc. Rev., 2011, 40
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,
,
,
L
L
2
(a) J. T. Kim, J. Butt and V. Gevorgyan, J. Org. Chem., 2004, 69
,
PdII
5638ꢀ5645; (b) D. Mujahidin and S. Doye, Eur. J. Org. Chem., 2005,
2689ꢀ2693.
Pd0L2
Ph
N
NH
Ph NHNH2
1a
I
3
4
O. Provot, A. Giraud, J.ꢀF. Peyrat, M. Alami and J.ꢀD. Brion,
Tetrahedron Lett., 2005, 46, 8547ꢀ8550.
HX
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Int. Ed., 2006, 45, 1034ꢀ1057.
L
L
L2PdIIX2
HOAc
PdII
L
O2
L
L
Ph PdII
N
NH
O2
PdII
L
5 (a) Y. Su, X. Sun, G. Wu and N. Jiao, Angew. Chem. Int. Ed., 2013, 52
,
II
HN NH
HX
Pd0L2
9808ꢀ9812; (b) T. Taniguchi, H. Zaimoku and H. Ishibashi, Chem. Eur.
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B. Aylward, J. Chem. Soc. C: Org., 1969, 1663ꢀ1665; (f) A. S. Demir,
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Org. Chem., 2005, 70, 2380ꢀ2383; (i) T. Varea, M. E. Gonzálezꢀ
IV
N2 + H2O
Ph
Ph
Ph
PdIIX
L
Ph PdIIX
Ph
3aa
L
III
L
L
L
Ph PdII
L
Ph
L = PPh3
2a
Ph
Núñez, J. RodrigoꢀChiner and G. Asensio, Tetrahedron Lett., 1989, 30
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Zou, Org. Biomol. Chem., 2014, 12, 6922ꢀ6926; (n) T. Jiang, S.ꢀY.
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,
Scheme 4 Plausible reaction mechanism
Conclusions
In summary, we have developed a new type of Sonogashira
cross coupling reaction by using commercially available
arylhydrazines as the arylation reagents to prepare internal
alkynes. This reaction is performed under mild conditions
without the addition of copper salt or base. The substrate scope
is broad and also, the utilization of 1 atm of O2 as the
environmentally benign oxidant makes the protocol very
attractive for both academia and industry. Further investigations
to gain a detailed mechanistic understanding of this reaction are
currently underway.
6
(a) Y. Chen, S. Guo, K. Li, J. Qu, H. Yuan, Q. Hua and B. Chen, Adv.
Synth. Catal., 2013, 355, 711ꢀ715; (b) P. Yao, Appl. Organomet.
Chem., 2014, 28, 194ꢀ197; (c) Z. Peng, G. Hu, H. Qiao, P. Xu, Y. Gao
and Y. Zhao, J. Org. Chem., 2014, 79, 2733ꢀ2738; (d) F. Akiyama, H.
Miyazaki, K. Kaneda, S. Teranishi, Y. Fujiwara, M. Abe and H.
Notes and references
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