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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Palladium(II)-Catalyzed Synthesis of 2-(Biphenyl-2-yloxy)pyridines and N-Pyridylcarbazoles via Carbon-Hydrogen Bond Activation

Lin, Pi-shan 06 July 2011 (has links)
This thesis is composed of two parts. The palladium-catalysted synthesis of 2-arylphenols and carbazoles via carbon-hydrogen (C-H) bond activation 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 Ag2CO3, one equivalent of p-benzoquinone (BQ), and four equivalents of DMSO with (or without) H2O at 130-140 oC for 48 h in dried CH2Cl2 gave the ortho-arylated 2-phenoxypyridines in modest to excellent yields. The investigation of kinetic isotope effect (kH/kD) is determined to be 5.25, which indicates that C-H bond cleavage occurs in the rate-determining step. 2-(Biphenyl-2-yloxy)pyridines was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-arylphenols to demonstrate the pyridine is a removable directing group. On the other hand, a novel one-pot synthesis for N-pyridylcarbazoles by the reaction of N-phenylpyridin-2-amines with potassium aryltrifluoroborates using Pd(OAc)2 as the catalyst is presented. For instance, reaction of N-phenylpyridin-2-amines with four equivalents of potassium aryltrifluoroborate under the optimal reaction condition gave N-pyridylcarbazoles in 67% yield along with N-(biphenyl-2-yl)pyridin-2-amine in 13% yield. The investigation of kinetic isotope effect (kH/kD) for first C-H bond activation/C-C bond formation step is determined to be 2.14, and that of the second C-H bond activation/C-N bond formation steps is 1.18. On the basis of KIE analysis, it might indicate that first C-H activation undergo direct C-H bond cleacage, and second step should be via electrophilic aromatic substitution.

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