Copper-Mediated C4-Benzylations of 5-Aminopyrazoles with 3-Indoleacetic Acids

Herein, we present a copper-mediatedC4-benzylation of5-aminopyrazoleswith 3-indoleacetic acids. Various benzylated 5-aminopyrazoles areprepared in good-to-excellent yields under basic and ligand-free conditionsin the presence of copper acetate. Moreover, this benzylation methodis applicable to other substrates, including naphthylamine, 2-aminochromen-4-one,and enamines. Some products exhibit antiproliferative activities againstcancer cell lines. In addition, the C4-benzylated products are cyclizedinto 1H-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 withlarge Stokes shifts.

Automated summary

In this study, a copper-mediated C4-benzylation reaction of 5-aminopyrazoles with 3-indoleacetic acids was presented. Various benzylated 5-aminopyrazoles were synthesized in good-to-excellent yields under basic and ligand-free conditions in the presence of copper acetate. The benzylation method was also applied to other substrates and showed potential antiproliferative activities against cancer cell lines. Moreover, the C4-benzylated products underwent cyclization with aldehydes to form 1H-pyrazolo-[4 ',3 ':6,7]-azepino-[3,4-b]-indoles via one-pot two-step processes. The cyclized products exhibited fluorescence emissions with large Stokes shifts.