A Versatile Pd-Catalyzed Alkyne Annulation Process for Benzo[a]carbazoles and their Anticancer Analogues.

A Pd-catalyzed, simple, and divergent approach for the direct synthesis of benzo[a]carbazoles from internal alkynes and N-tosyl-iodoindoles has been demonstrated. This methodology highlights the influences of reaction media and temperature for the synthesis of either N-protected or N-deprotected benzo[a]carbazoles. This cascade strategy provides a series of electronically different benzo[a]carbazoles with good yields. The synthesized benzo[a]carbazoles were evaluated for in vitro anticancer activity against human lung cancer A549 cells and human breast cancer MDA-MB-231 cells. Notably, two of the representative analogues displayed potent anticancer activity against both cancer cell lines.