Synthesis of Benzo[a]carbazoles from 2-Arylindoles via a Sequential Propargylation, Propargyl-Allenyl Isomerization, and 6 pi-Electrocyclization

摘要

An efficient two-step synthetic approach of benzo[a]carbazoles from 2-arylindoles has been developed. The first step is a propargylation of 2-arylindoles at the 3-position catalyzed by montmorillonite K-10 in benzene. The second step is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed sequential propargyl-allenyl isomerization and a concomitant 6 pi-electrocyclization process involving two aromatic pi-bonds.