Organic Letters
Letter
of diphenyl 2,4-pyridine dicarboxylate (1J) (Scheme 4). The
first palladium-catalyzed coupling reaction at the C2 position of
In summary, we have developed a palladium-catalyzed
decarbonylative biaryl coupling of phenyl 2-azinecarboxylates
and arylboronic acids. Various 2-azinecarboxylates can undergo
decarbonylative coupling to furnish 2-arylpyridines. Further
development and application of this decarbonylative reaction
Scheme 4. Diarylpyridine Synthesis by Sequential
Decarbonylative Coupling
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methodology will be reported in due course.
ASSOCIATED CONTENT
Supporting Information
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Detailed experimental procedures and spectral data for
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all compounds, including scanned image of H and
C
AUTHOR INFORMATION
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Notes
The authors declare no competing financial interest.
the pyridine smoothly provided 2-arylpyridine 3Ja in 61% yield.
In this reaction, 4-arylpyridine was not detected at all as judged
by H NMR analysis. Transformation of the remaining ester
ACKNOWLEDGMENTS
This work was supported by the ERATO program from JST
K.I.) and JSPS KAKENHI (Grant Nos. JP16H01011 and
JP16H04148 (to J.Y.). K.M. was supported by the Early Bird
Program of Waseda University. We thank Mr. Ryosuke Takise
Nagoya University) for providing starting materials. ITbM is
supported by the World Premier International Research Center
WPI) Initiative, Japan.
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functionality was accomplished by nickel-catalyzed decarbon-
ylative coupling at the C4 position of the pyridine to provide
(
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2
,4-diarylpyridine 4 in 65% yield. Thus, the developed ester-
based coupling reactions would be potentially useful for the
selective synthesis of highly arylated pyridines.
(
A plausible mechanism of the present coupling reaction,
which is based on our previous nickel catalysis, is shown in
(
7
,10
Figure 2.
First, an active Pd(0) species would be generated
REFERENCES
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1
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(
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(
(
(
Figure 2. Plausible reaction mechanism.
(c) Gooßen, L. J.; Paetzold, J. Angew. Chem., Int. Ed. 2004, 43, 1095.
(
d) Gooßen, L. J.; Paetzold, J. Adv. Synth. Catal. 2004, 346, 1665.
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by dimerization of arylboronic acids. To this Pd(0) species,
the C(acyl)−O bond of the ester undergoes oxidative addition
to give an acyl−Pd(II) species. Then, diarylpalladium would be
generated by transmetalation of arylboronic acids using base,
followed by CO migration. Finally, reductive elimination
affords the desired biaryl product and Pd(0)−CO, which can
then decarbonylate to regenerate the active Pd(0) species.
2
(
015, 6, 7508.
8) (a) Amaike, K.; Muto, K.; Yamaguchi, J.; Itami, K. J. Am. Chem.
Soc. 2012, 134, 13573. Other catalytic reactions using Ni/dcype:
b) Muto, K.; Yamaguchi, J.; Itami, K. J. Am. Chem. Soc. 2012, 134,
(
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69.
(9) (a) Takise, R.; Muto, K.; Yamaguchi, J.; Itami, K. Angew. Chem.,
Int. Ed. 2014, 53, 6791. (b) Koch, E.; Takise, R.; Studer, A.;
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Org. Lett. XXXX, XXX, XXX−XXX