Palladium(II)-Catalyzed Direct Ortho Arylation of 4-Methyl-<i>N</i>-phenylpyridin-2-amines via C–H Activation/C–C Coupling and Synthetic Applications
作者:Jean-Ho Chu、Hao-Ping Huang、Wen-Ting Hsu、Shih-Tien Chen、Ming-Jung Wu
DOI:10.1021/om401195w
日期:2014.3.10
The direct ortho arylation of 4-methyl-N-phenylpyridin-2-amines via palladium(II)-catalyzed C-H activation is described. Treatment of 4-methyl-N-phenylpyridin-2-amine with potassium aryltrifluoroborate using 10 mol % of palladium(II) acetate as the catalyst, 2 equiv of copper(II) acetate as the oxidant, and 1 equiv of p-benzoquinone in tert-butyl alcohol gave ortho-arylated products in modest to excellent yields. This reaction shows good functional group compatibility. A series of H-1 NMR titration experiments and controlled experiments elucidating the reaction mechanism were carried out. The key intermediate, 4-methyl-N-phenylpyridin-2-amine palladacycle, was isolated and characterized by X-ray crystallography. The advanced transformations of ortho-phenylated 4-methyl-N-phenylpyridin-2-amine to N-(4-methylpyridin-2-yl)-9H-carbazole, biphenyl-2-amine, and 3-methyl-6-phenylpyrido[1,2-a]benzimidazole were successfully demonstrated as potential synthetic applications.