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 °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 0 -nitrobiphenyl-2-yloxy)pyridine, was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-(4nitrophenyl)phenol in 79% yield, demonstrating that pyridine is a removable directing group.

diphenylisoxazole (1) using Pd(OAc) 2 as a reagent in acetic acid leading to the isoxazole palladacycle I was described. Ortho aryl-and alkyl-substituted 3,5-diphenylisoxazoles 3a-f and 5a-i were synthesized by the reaction of I with Various boronic acids 2a-f and 4a-i, respectiVely. p-Benzoquinone was found to be the best oxidant and 1,4-dioxane the best solVent for the transmetalation-reductiVe-elimination step of I with boronic acids.Isoxazole-containing molecules have received considerable attention, because they are excellent precursors in transforming to a variety of bifunctional compounds 1 and show diverse biological activities. 2 Recently, functionalizations of aryl C-H bonds using organometallic reagents, 3 olefins, 4 peroxides, 5 or diethyl azodicarboxylate 6 catalyzed by transition metals have been investigated intensively. 7 In order to achieve the orthoselective C-H bond functionalization, a functional-groupcontaining heteroatom, such as a pyridyl, imine, acetyl, or acetoamino group, is required to form a stable metal complex. According to these observations, we anticipate that isoxazole could provide a good anchor for ortho metalation of aromatic rings and would allow us to prepare a variety of multiply substituted isoxazoles. We herein report the ortho arylation and

A one-pot synthesis of ortho-arylated 9-(pyridin-2-yl)-9H-carbazoles via C–H bond activation is presented. Silver nitrate and tert-butyl alcohol were found to be the best oxidant and solvent for the process, respectively. The product yields are from modest to excellent, and the reaction showed sufficient functional group tolerance. p-Benzoquinone served as an important ligand for the transmetalation and reductive elimination steps in the catalytic process. The key intermediate of the reaction, a 9-(pyridin-2-yl)-9H-carbazole palladacycle, was isolated, and its structure was unequivocally confirmed by X-ray crystallography. No kinetic isotope effect (k H/k D = 1.00 ± 0.17) for the C–H bond activation step was observed. In addition, a Hammett experiment gave a negative ρ value, −2.16 ± 0.02. The directing group, pyridinyl, was demonstrated to be a removable functional group. Finally, a rational catalytic mechanism is presented on the basis of all experimental evidence.

A biscalixarene framework, without long alkyl chains, has been readily synthesized in three steps starting from the parent calix[4]arene. The biscalix[4]arene 1 was able to form organogels in various alcoholic solvents; furthermore, it exhibited an excellent phase selective gelation property that is potentially useful in oil spill recovery.

We report herein the synthesis of a fluorescence turn-on chemosensor, 25,27

A direct ortho aroylation of 2-phenoxypyridines with aldehydes leading to aryl ketones by the use of palladium(II) acetate, tert-butyl hydroperoxide, and chlorobenzene as the catalyst, oxidant, and solvent, respectively, is presented. Intra-and intermolecular kinetic isotope effects, radical trapping, and controlled experiments were carried out to support the proposed catalytic mechanism for the reaction. Syntheses of (2-hydroxyphenyl)-(phenyl)methanones and 1-hydroxy-9H-fluoren-9-ones directed from ortho-aroylated 2-phenoxypyridines were demonstrated.

The hypervalent iodine(III) reagent-induced the direct intramolecular C-N cyclization of N-(biphenyl)pyridin-2-amines to 6-arylbenzimidazoles and N-pyridinyl-9H-carbazoles is presented. The substituent electronic effects governing the formation of benzimidazoles and carbazoles from the reaction of N-(biphenyl)pyridin-2-amines with hypervalent iodine(III) reagents is investigated. Radical trapping and UV-vis spectroscopic experiments on the detection of the cation radical are carried out. Rational mechanisms for these reactions are presented. The selective intramolecular C-N and C-O cyclization of N-(biphenyl)acetamides based on the substituent electronic effects is also presented.

A direct arylation of pyrazolo­[1,5-a]­pyridines with aryl iodides selectively occurring at the C-3 and C-7 positions via palladium-catalyzed C–H activation is described. In these reactions, (a) cesium­(I) fluoride and (b) silver­(I) carbonate were employed as the additive to afford 3- and 7-arylated pyrazolo­[1,5-a]­pyridines, respectively, in modest to good yields. These reactions showed good compatibility with functional groups, and the catalytic mechanisms of these reactions were proposed. Finally, the synthetic application on the potent p38 kinase inhibitors was demonstrated.