New Cyclization Route to the Skeletons of Lennoxamine and Chilenine

Abstract

A new cyclization route, triggered by epoxide opening, has been performed to provide the key intermediates for isoindolobenzapine alkaloids, lennoxamine and chilenine. The epoxide was prepared by the Stille reaction using vinyltributylstannane and the following dioxirane treatment. Cyclization under the treatment of BF₃ · OEt₂ provided an azepine moiety, and the oxidative cyclization toward the known precursor for the alkaloids has been achieved by reaction with a stoichiometric amount of Pd(OAc)₂. This formal synthesis suggests a new route to the alkaloids.

Keywords:

• Chilenine
• epoxide
• lennoxamine
• oxidative cyclization
• palladium acetate

ACKNOWLEDGMENTS

This work was supported by a Korea Research Foundation Grant funded by the Korea Government (MOEHRD, Basic Research Promotion Fund) (KRF-2005-070-C00073), and we appreciate the Center for Research Facilities, Chungnam National University, for the permission to use the NMR facilities.