Palladium(II)-catalyzed one-pot syntheses of 9-(pyridin-2-yl)-9H-carbazoles through a tandem C-H activation/C-X (X=C or N) formation process.
A new one-pot synthesis of 9-(pyridin-2-yl)-9H-carbazoles through the simultaneous C-H activation and palladium(II)-catalyzed cross-coupling of N-phenylpyridin-2-amines with potassium aryltrifluoroborates is presented. Silver acetate and 1,4-dioxane proved to be the best oxidant and solvent, 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 kinetic isotope effects (k(H)/k(D)) for the first and second C-H activation/C-C or C-N formation steps were measured as 2.14 and 1.18, respectively. Finally, a rational catalytic mechanism is presented based on all experimental evidence.
Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan 804, Taiwan.
Jean-Ho
JH
Chu
Pi-Shan
PS
Lin
Ya-Ming
YM
Lee
Wei-Ting
WT
Shen
Ming-Jung
MJ
Wu
D002227:Carbazoles / Q000737:chemistry*; D002384:Catalysis; D003432:Cross-Linking Reagents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*
D002227:Carbazoles; D003432:Cross-Linking Reagents; C041514:carbazole; D010165:Palladium