C O M M U N I C A T I O N S
a
Table 2. Palladium-Catalyzed Alkenylation of Quinoline-N-oxides
Scheme 2. Plausible Mechanism for the Direct Coupling Reaction
catalyzed C-H bond activation, providing 2-alkenylated quinolines
and 1-alkenylated isoquinolines in chemo- and regioselective
manners under external-oxidant-free conditions. Investigations of
the elucidation of the reaction pathway in detail and extending the
scope of the reaction to other substrates are in process.
Acknowledgment. We are grateful to the NSF of China
(20772114), the NSF of Henan (082300423201), and the Outstand-
ing Doctoral Dissertation Fund of Zhengzhou University for
financial support of this research. We thank Professor Kuiling Ding
from Shanghai Institute of Organic Chemistry for valuable com-
ments on this paper.
Supporting Information Available: Detailed experimental proce-
dures and spectroscopic characterization data for all new compounds.
This material is available free of charge via the Internet at http://
pubs.acs.org.
a
Reaction conditions: 1 (1 mmol), 2 (5 mmol), Pd(OAc)
2
(5 mol %),
b
References
NMP (1 mL), 110 °C, 20 h. Isolated yields.
(
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was performed. One equivalent of N-oxide 4, prepared using a slight
10
modification of the protocol reported by Heimg a¨ rtner, was added
to a reaction system consisting of 1 equiv of 3-methylquinoline-
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conditions. Products 3a and 3f were detected by HPLC analysis of
the reaction mixture (Scheme 1). These results are incompatible
with the intramolecular redox reaction and suggest that alkenylated
quinoline-N-oxides act as the oxidant to convert Pd(0) into Pd(II),
thus completing the catalytic cycle.
A plausible mechanism for the direct coupling of quinoline-N-
oxides with acrylate is shown in Scheme 2. First, aryl-Pd complex
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and subsequent electrophilic attack at the 2-position carbon atom.
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(
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4
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2
followed by syn insertion gives intermediate II. ꢀ-Hydride
(
11
elimination of II forms palladium hydride and intermediate III.
Oxidation of palladium hydride by intermediate III affords products
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(
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3
and palladium acetate to complete the catalytic cycle.
The present report reveals for the first time that quinoline-N-
oxides serve as both the inducing platform and the oxidant in Pd-
JA902762A
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