An unprecedented organocatalytic cascade aldimine condensation/[1,6]-hydride transfer/Mannich-type cyclization of indole-2-carbaldehydes with o-aminoanilines was developed to assemble indole-2,3-fused diazocanes in one step.
A facile procedure for the synthesis of benzannelated diazacycloalkanes 3 is elaborated on the basis of reductive cleavage of 1,2-polymethylenebenzimidazoles 2 with DIBAL-H. The reduction of the corresponding salts prepared by treatment of 1,2-polymethylenebenzimidazoles 2 with methyl iodide proceeded differently affording exclusively o-phenylenediamines 10. The limitations and scope of the method