Synthesis of CF(3)-Indazoles via Rh(III)-Catalyzed C-H [4+1] Annulation of Azobenzenes with CF(3)-Imidoyl Sulfoxonium Ylides.

An efficient Rh(III)-catalyzed C-H activation of azobenzenes and subsequent [4+1] cascade annulation with CF(3)-imidoyl sulfoxonium ylides was developed, yielding diverse CF(3)-indazoles. This protocol featured easily available starting materials, excellent functional group tolerance and high efficiency. Moreover, the antitumor activities of selected CF(3)-indazoles against human cancer cell lines were also studied, and the results indicated that several compounds displayed considerable antiproliferative activities.