disclose the first C-2-selective C–H alkenylation of quinoline N-oxides catalyzed using a heterogeneous palladium catalyst. The protocol does not require the use of an external oxidant and it is applicable to an ample substrate scope always showing excellent site selectivity. This process is made accessible by the use of a specific 1,2,3-triazolium-tagged heterogeneous polymeric catalytic system. The
A novel and efficient protocol for the C-2selectiveolefination of pyridines via a palladium-catalyzed oxidative cross-coupling reaction has been developed. A wide range of pyridines and olefin substrates including acrylic ester, styrene, and acrylamide are compatible. The products are highly useful building blocks for the synthesis of bioactive alkaloid natural products and drug molecules.
Synthesis of 2-Alkenylquinoline by Reductive Olefination of Quinoline <i>N</i>-Oxide under Metal-Free Conditions
作者:Hong Xia、Yuanhong Liu、Peng Zhao、Shaohua Gou、Jun Wang
DOI:10.1021/acs.orglett.6b00522
日期:2016.4.15
Synthesis of 2-alkenylquinoline by reductive olefination of quinoline N-oxide undermetal-freeconditions is disclosed. Practically, the reaction could be performed with quinoline as starting material via a one-pot, two-step process. A possible mechanism is proposed that involves a sequential 1,3-dipolar cycloaddition and acid-assisted ring opening followed by a dehydration process.
The direct cross-coupling of quinoline-N-oxides with olefin derivatives has been realized using palladium acetate as the catalyst in the absence of external ligand and oxidant to give the corresponding 2-alkenylated quinolines and 1-alkenylated isoquinolines chemo- and regioselectively in 27-95% yield. The catalytic process is proposed to proceed via direct C-H bond activation of the quinoline-N-oxide with Pd(OAc)(2) followed by Heck coupling with the olefin. The resultant N-oxide of the alkenylated quinoline can oxidize the reduced Pd(0) to regenerate the Pd(11) active species and simultaneously release the 2-alkenylated quinoline without using any external oxidants and reductants.
Waste-minimized synthesis of C2 functionalized quinolines exploiting iron-catalysed C–H activation