Polycyclic Indoline-Benzodiazepines through Electrophilic Additions of -Imino Carbenes to Troger Bases

Polycyclic indoline-benzodiazepines can be accessed through the intermolecular reaction of Troger bases with N-sulfonyl-1,2,3-triazoles. Under Rh-II catalysis, -imino carbenes are generated and a subsequent cascade of [1,2]-Stevens, Friedel-Crafts, Grob, and aminal formation reactions yield the polycyclic heterocycles as single isomers (d.r.>49:1, four stereocenters including two bridgehead Natoms). Further ring expansion by insertion of a second -imino carbene leads to elaborated polycyclic 9-membered-ring triazonanes.