One-Pot Synthesis of Benzo[ c]phenanthridine Alkaloids from 7-Azabenzonorbornadienes and Aryl Nitrones

Org Lett. 2023 Jun 2;25(21):3853-3858. doi: 10.1021/acs.orglett.3c01192. Epub 2023 May 18.

Abstract

An efficient synthesis of benzo[c]phenanthridine alkaloids via a synergistic combination of C-C bond formation and a cycloaromatization reaction is described. Aryl nitrones react with 7-azabenzonorbornadienes in the presence of a Rh(III) catalyst, providing pharmaceutically useful benzo[c]phenanthridine derivatives in good to moderate yields. Using this methodology, highly useful alkaloids such as norfagaronine, norchelerythrine, decarine, norsanguinarine, and nornitidine were prepared in a single step.