We herein report a highly regioselective reaction for the palladium-catalyzed oxidative acylation of carbazole derivatives with various aromatic and aliphatic aldehydes as the acyl source. The carbazole derivatives are N-protected with an easily removable pyridine moiety, which directs the Pd-catalyzedortho acylation to occur at the C-1 and C-8 positions. The reactions of dibromo- and diiodo-substituted
Transition metal-catalyzed regioselective functionalization of carbazoles and indolines with maleimides
作者:Eun Hee Cho、Muhammad Saeed Akhtar、Mohammad Aslam、Raju S. Thombal、Xin Li、Jae-Jin Shim、Yong Rok Lee
DOI:10.1039/d2ob01077a
日期:——
The directing group-assisted regioselective C–H activation of carbazoles and indolines is achieved via transition metal-catalyzed reactions. This C–H functionalization protocol provides a rapid approach to install diversely functionalized succinimide groups at the C-1 position of the carbazole moiety. In addition, this protocol demonstrates the intrinsic reactivity of indolines in providing C-2 su
CuCl-Catalyzed Ullmann-Type C–N Cross-Coupling Reaction of Carbazoles and 2-Bromopyridine Derivatives
作者:Xiangdong Zhao、Yuanbin She、Kun Fang、Guijie Li
DOI:10.1021/acs.joc.6b02595
日期:2017.1.20
A CuCl-catalyzed Ullmann-type C-N cross coupling reaction of carbazoles and 2-bromopyridine deriva tives has been developed for the synthesis of N-heteroarylcarbazole derivatives employing 1-methyl-imidazole and t-BuOLi as ligand and base, respectively, both of which are found to significantly promote the reaction. Low cost and low loading of both catalyst and ligand, together with high reaction yields, render this practical reaction to be suitable for large-scale preparations and could be useful in material science.
Direct Ortho Arylation of 9-(Pyridin-2-yl)-9<i>H</i>-carbazoles Bearing a Removable Directing Group via Palladium(II)-Catalyzed C–H Bond Activation
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 rho 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.