Fe(III)-Catalyzed Bicyclization of Yne-Allenones with Indoles for the Atom-Economic Synthesis of 3-Indolyl Cyclobutarenes

Heng Li, Wen-Juan Hao, Guigen Li,* Shu-Jiang Tu, Bo Jiang*

A new Fe(III)-catalyzed bicyclization reaction of yne-allenones with indoles has been established, enabling the direct construction of cyclobuta[a]naphthalen-4-ols with an all-carbon quaternary center in good yields. This reaction was performed by using low-cost FeCl₃ as the catalyst and EtOH as the environmentally benign solvent, providing a green protocol for constructing cyclobutarene framework with a high degree of atom economy and functional group compatibility. The reaction mechanism was proposed through a [2 + 2] cycloaddition/1,6-conjugate addition cascade.

Front. Chem. 2018, 6, 599 (doi: 10.3389/fchem.2018.00599)