Imino-bridged heterocycles. III . Synthesis of mono-bridgehead substituted 11H-benzo[5,6]cyclohepta[1,2-c]pyridin-6,11-imines by regiospecific amine to olefin cyclizations

Employing regiospecific amine to endocyclic olefin and hydroxylamine to exocyclic olefin cyclizations, we have developed pathways to two isomeric, bridgehead methyl-substituted benzo5,6]cyclohepta1,2-c]pyridin-6,11-imines. Acid catalyzed cyclization of 5 to 6 was accomplished under exceedingly mild conditions (silica gel/chloroform), whereas, thermal cyclization of 20 to generate 21 was performed analogously to the dibenzoa,d]cyclohepten-5,10-imine system.