Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization
摘要:
An efficient synthesis of ortho-arylated 2-phenoxypyridines catalyzed by palladium acetate is described. Treatment of 2-phenoxypyridines with two and a half equivalents of potassium aryltrifluoroborate and 10 mol % of Pd(OAc)(2) in the presence of two equivalents of Ag(2)CO(3), one equivalent of p-benzoquinone (BQ), and four equivalents of DMSO with (or without) H(2)O at 130-140 degrees C for 48 h in dried CH(2)Cl(2) gave the ortho-arylated 2-phenoxypyridines in modest to excellent yields. p-Benzoquinone is found to be an important ligand and co-oxidant for the transmetalation reductive elimination step in the catalytic reaction. The investigation of kinetic isotope effect (k(H)/k(D)) is determined to be 5.25, which indicates that C H bond cleavage occurs in the rate-determining step. One of the arylated compounds, 2-(4'-nitrobiphenyl-2-yloxy)pyridine, was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-(4-nitrophenyl)phenol in 79% yield, demonstrating that pyridine is a removable directing group.
Palladium(II)-Catalyzed Ortho Arylation of 2-Phenoxypyridines with Potassium Aryltrifluoroborates via C−H Functionalization
摘要:
An efficient synthesis of ortho-arylated 2-phenoxypyridines catalyzed by palladium acetate is described. Treatment of 2-phenoxypyridines with two and a half equivalents of potassium aryltrifluoroborate and 10 mol % of Pd(OAc)(2) in the presence of two equivalents of Ag(2)CO(3), one equivalent of p-benzoquinone (BQ), and four equivalents of DMSO with (or without) H(2)O at 130-140 degrees C for 48 h in dried CH(2)Cl(2) gave the ortho-arylated 2-phenoxypyridines in modest to excellent yields. p-Benzoquinone is found to be an important ligand and co-oxidant for the transmetalation reductive elimination step in the catalytic reaction. The investigation of kinetic isotope effect (k(H)/k(D)) is determined to be 5.25, which indicates that C H bond cleavage occurs in the rate-determining step. One of the arylated compounds, 2-(4'-nitrobiphenyl-2-yloxy)pyridine, was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-(4-nitrophenyl)phenol in 79% yield, demonstrating that pyridine is a removable directing group.
Herein, we report the iron-catalyzed borylation of arylethers and aryl amines via cleavage of C–O and C–N bonds. This protocol does not require the use of Grignard reagents and displays a broad substrate scope, which allows the late-stage borylation. It also provides facile access to multisubstituted arenes through C–H functionalization using 2-pyridyloxy as the directing group.
Chromium-Catalyzed Regioselective Kumada Arylative Cross-Coupling of C(aryl)–O Bonds with a Traceless Activation Strategy
作者:Fei Fan、Jinghua Tang、Meiming Luo、Xiaoming Zeng
DOI:10.1021/acs.joc.8b02104
日期:2018.11.2
We report here the chromium-catalyzed regioselective Kumada arylative cross-coupling of C(aryl)-O bonds at ambient temperature. By using a simple and low-cost chromium(II) chloride salt as a precatalyst, accompanied by a 2-pyridyl ligation, the catalytic cleavage and arylative coupling of C(aryl)-O bonds were achieved with a traceless activation strategy, overcoming the regioselectivity obstacle when several C-O bonds coexist in the Kumada coupling system.