Copper-Mediated C4-Benzylations of 5-Aminopyrazoles with 3-Indoleacetic Acids
Qiwen Gao, Jinhong Tian, Kangmei Wen, Chen Chen, Xingang Yao, Jianxin Pang, Xiaodong Tang
Abstract
Herein, we present a copper-mediated C4-benzylation of 5-aminopyrazoles with 3-indoleacetic acids. Various benzylated 5-aminopyrazoles are prepared in good-to-excellent yields under basic and ligand-free conditions in the presence of copper acetate. Moreover, this benzylation method is applicable to other substrates, including naphthylamine, 2-aminochromen-4-one, and enamines. Some products exhibit antiproliferative activities against cancer cell lines. In addition, the C4-benzylated products are cyclized into 1 H -pyrazolo[4′,3′:6,7]azepino[3,4- b ]indoles with aldehydes via one-pot two-step processes; notably, the cyclized products exhibit fluorescence emissions with large Stokes shifts.