Skeletal Formation of Carbocycles with CO 2 : Selective Synthesis of Indolo[3,2- b ]carbazoles or Cyclophanes from Indoles, CO 2 , and Phenylsilane.

The catalytic reactions of indoles with CO 2 and phenylsilane afforded indolo[3,2- b ]carbazoles, where the fused benzene ring was constructed by forming two C-H bonds and four C-C bonds with two CO 2 molecules via deoxygenative conversions. Nine-membered cyclophanes made up of three indoles and three CO 2 molecules were also obtained, where the cyclophane framework was constructed by forming six C-H bonds and six C-C bonds. These multicomponent cascade reactions giving completely different carbocycles were switched simply by choosing the solvent, acetonitrile or ethyl acetate.