Palladium(II)-Catalyzed Direct Ortho Arylation of 4‑Methyl‑N‑phenylpyridin-2-amines via C–H Activation/C–C Coupling and Synthetic Applications
datasetposted on 10.03.2014, 00:00 by Jean-Ho Chu, Hao-Ping Huang, Wen-Ting Hsu, Shih-Tien Chen, Ming-Jung Wu
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 1H 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.
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Synthetic ApplicationsTheortho arylationPalladiumtransformationmethylactivationoxidantmolyieldseriespalladacyclecrystallographyMethylreaction mechanismbiphenyl2 equivcatalystpalladiumexperiments elucidatingacetateOrtho Arylation1 H NMR titration experimentsgroup compatibilityActivationapplicationpotassium aryltrifluoroborate1 equiv