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Palladium (II)-Catalyzed Ortho Arylation of 9-(Pyridin-2-yl)-9H-carbazoles via C-H Bond Activation And Mechanistic Investigation

A one-pot synthesis of ortho-arylated 9-(pyridin-2-yl)-9H-carbazoles via C-H bond activation, in which palladium(II)-catalyzed cross-coupling of 9-(pyridin-2-yl)-9H-carbazoles with potassium aryltrifluoroborates is presented. Silver nitrate and tert-butanol were proved to be the best oxidant and solvent for the process, respectively. The product yields fluctuated 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, 9-(pyridin-2-yl)-9H-carbazole palladacycle was isolated and confirmed by X-ray crystallography. The kinetic isotope effect (kH/kD) for the C-H bond activation step was measured as 0.87. In addition, Hammett experiment gave a negative rho value, -2.14 with a reasonable correlation (R2 = 0.90). The directing group, pyridyl was demonstrated as a removable functional group. Finally, a rational catalytic mechanism is presented based on all experimental evidence.

Identiferoai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0709112-170941
Date09 July 2012
CreatorsWu, Chung-chiu
ContributorsJen-Chieh Hsieh, Ming-Jung Wu, Michael Y. Chiang
PublisherNSYSU
Source SetsNSYSU Electronic Thesis and Dissertation Archive
LanguageCholon
Detected LanguageEnglish
Typetext
Formatapplication/pdf
Sourcehttp://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0709112-170941
Rightsuser_define, Copyright information available at source archive

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