Organic Letters
Letter
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Scheme 4. Further Studies on the Mechanism
down the competitive proto-demetalation prior to trans-
metalation. Additionally, we found that both radical scavengers
(TEMPO or BHT) and radical clocks (diallyl ether or 1,1-
diphenyethylene) had limited impact on the yields of this
reaction (Scheme 4, eq 3). These preliminary studies suggested
in situ formation of an alkylzinc reagent as an intermediate for the
coupling reaction, although the possibility of involvement of alkyl
radical intermediate as a minor path could not be ruled out.
In summary, a straightforward and ligand-free method for the
Pd-catalyzed electrochemical coupling between alkyl and allylic
halides has been developed. This protocol is efficient for the
coupling reaction of substituted allylic halides with a variety of
alkyl halides, including unactivated primary, secondary, and
tertiary halides as well as activated halides. Prior formation of an
organiczinc reagent, strict exclusion of moisture and air, and
protection−deprotection of acidic hydrogen in the substrates are
avoided. Further investigation to determine the mechanism of
this reaction and to expand its scope is underway in our
laboratory.
̆
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2
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ASSOCIATED CONTENT
* Supporting Information
̌
̌ ́
(7) Lipshutz, B. H.; Abela, A. R.; Boskovic, Z. V.; Nishikata, T.; Duplais,
C.; Krasovskiy, A. Top. Catal. 2010, 53, 985.
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■
S
The Supporting Information is available free of charge on the
D. Tetrahedron 2000, 56, 9527. (c) Schafer, H. J.; Bard, A. J.; Stratmann,
̈
Experimental procedures and spectroscopic data (PDF)
M. Organic Electrochemistry, Encyclopedia of Electrochemistry; Wiley-
VCH: Weinheim, 2004. (d) Sperry, J. B.; Wright, D. L. Chem. Soc. Rev.
2006, 35, 605. (e) Yoshida, J.; Kataoka, K.; Horcajada, R.; Nagaki, A.
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AUTHOR INFORMATION
■
Corresponding Author
ORCID
Mohle, S. Angew. Chem., Int. Ed. 2015, 54, 6398.
̈
Notes
(9) (a) Huang, J.-M.; Wang, X.-X.; Dong, Y. Angew. Chem., Int. Ed.
2011, 50, 924. (b) Huang, J.-M.; Dong, Y. Chem. Commun. 2009, 3943.
(c) Huang, J.-M.; Ren, H.-R. Chem. Commun. 2010, 46, 2286.
(10) (a) Ohmiya, H.; Yorimitsu, H.; Oshima, K. Org. Lett. 2006, 8,
3093. (b) Jana, R.; Pathak, T. P.; Sigman, M. S. Chem. Rev. 2011, 111,
1417.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(11) Kurono, N.; Sugita, K.; Takasugi, S.; Tokuda, M. Tetrahedron
1999, 55, 6097 and references therein.
We are grateful to the National Natural Science Foundation of
China (Grant Nos. 21372089 and 201672074) for financial
support.
(12) It was found that the Pd(OAc)2-catalyzed Heck reaction could be
dramatically accelerated by the current passed through the reaction; see:
(a) Tian, J.; Moeller, K. D. Org. Lett. 2005, 7, 5381. (b) Moeller, K. D.
Organometallics 2014, 33, 4607.
(13) (a) Zhang, P.; Zhang, W.; Zhang, T.; Wang, Z.; Zhou, W. J. Chem.
Soc., Chem. Commun. 1991, 491. (b) Marshall, J. A. Chem. Rev. 2000,
100, 3163.
(14) (a) Keh, C. C. K.; Wei, C.; Li, C.-J. J. Am. Chem. Soc. 2003, 125,
4062. (b) Fleming, F. F.; Gudipati, S.; Aitken, J. A. J. Org. Chem. 2007,
72, 6961 and references therein. (c) Yang, Y.-S.; Shen, Z.-L.; Loh, T.-P.
Org. Lett. 2009, 11, 1209. For examples of generating an analogous alkyl
intermediate using In/Cu couple, see: (d) Shen, Z.-L.; Loh, T.-P. Org.
Lett. 2007, 9, 5413. (e) Shen, Z.-L.; Yeo, Y.-L.; Loh, T.-P. J. Org. Chem.
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