Synthesis of 2-boryl- and silylindoles by copper-catalyzed borylative and silylative cyclization of 2-alkenylaryl isocyanides.
We have developed a method for the synthesis of 2-borylindoles via the copper(I)-catalyzed borylative cyclization of 2-alkenylphenyl isocyanides using diboronate. The reaction proceeds at room temperature under neutral conditions and exhibits high tolerance to functional groups, such as Br, CO(2)R, COR, CONMe(2), and CN. The 2-borylindoles synthesized in the present study can be elaborated into an array of indole-based derivatives, for example, through the Suzuki-Miyaura reaction. The utility of this method is demonstrated in the rapid synthesis of a kinase inhibitor, paullone. The reaction can be extended to the synthesis of 2-hydride indole and 2-silylindole by using hydroboronate (or hydrosilane) and silylboronate, respectively. Under these copper-catalyzed conditions, a quinoxaline ring system can also be constructed by using 1,2-isocyanobenzene as a substrate.
Tobisu
Mamoru
M
Frontier Research Base for Global YoungResearchers, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
Fujihara
Hirokazu
H
Koh
Keika
K
Chatani
Naoto
N