Regio- and Stereoselective Synthesis of the Core Structure of Hexahydrobenzo[c]phenanthridine Alkaloids via Redox-Neutral Cp*Rh(III)-Catalyzed C–H/N–H Annulation of Cyclic Alkenes with Benzamides

Abstract

A highly stereo- and regioselective synthesis of the core skeleton of hexahydrobenzo[ c ]phenanthridine-type alkaloids is reported herein for the first time. A wide range of substrate scope, excellent functional group tolerance, and good to excellent yields were observed. This protocol gives very concise and efficient access to the core skeleton of chelidonine alkaloids as compared to the earlier approaches.

Co(II)‐Catalysed C−H/N−H Annulation of Cyclic Alkenes with Benzamides at Room Temperature: An Easy Access to the Core Skeleton of Hexahydrobenzo[c]phenanthridine‐type Alkaloids

“…Use of bicyclic olefinic systems has attracted our attention, because it can be used to synthesize hexahydrobenzo[ c ]phenanthridine type alkaloids which are widely prevalent in many natural products such as ( + )‐corynoline ( + )‐corynoloxine and ( + )‐chelamine etc (Figure 1). [9] Till now there is only one report [10] on the rhodium catalyzed synthesis of hexahydrobenzo[ c ]phenanthridine moiety by using bicyclic olefins.…”