Synthesis 2009(22): 3757-3764  
DOI: 10.1055/s-0029-1217014
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Palladium(II)-Catalyzed ortho Arylation of 2-Phenylpyridines with Potassium Aryltrifluoroborates by C-H Functionalization

Jean-Ho Chua, Shiang-Lin Tsaib, Ming-Jung Wu*a
a Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan 804, Taiwan
Fax: +886(7)5253909; e-Mail: mijuwu@faculty.nsysu.edu.tw;
b Faculty of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung, Taiwan 807, Taiwan
Further Information

Publication History

Received 8 June 2009
Publication Date:
23 September 2009 (online)

Abstract

An efficient one-pot synthesis of ortho-arylated 2-phenylpyridine and pyridine derivatives by use of potassium aryltri­fluoroborates is presented. The optimal reaction conditions are as follows: the 2-phenylpyridine or pyridine derivative is treated with 2.5 equivalents of a potassium aryltrifluoroborate in the presence of 10 mol% palladium(II) acetate, three equivalents of copper(II) acetate, and two equivalents of p-benzoquinone in 1,4-dioxane at 120 ˚C for 24 hours. p-Benzoquinone is an important co-oxidant in the transmetalation-reductive elimination step. The kinetic isotope effect (k H/k D) for the C-H bond activation was determined to be 1.09. It indicates that the C-H bond cleavage does not occur in the rate-determining step.

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Four different equivalents (1, 2, 2.5, and 3) of potassium trifluoro(phenyl)borate(2a) were examined under the reaction conditions, and the yield of product 3a was determined to be 52%, 68%, 74%, and 75%, respectively. According to these results, 2.5 equivalents of potassium aryltrifluoroborates were chosen to be the optimal amount.

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CCDC 715155 contains the supplementary crystallographic data of compound 3c. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

23

The optimal reaction conditions reported in the literature were followed; see ref. 9g.