Unprecedented Bridged Annulation Approach to the Construction of 5,6-Dihydro-4H-benzo[kl]acridines

Abstract

A general and novel “bridged annulation” methodology for the synthesis of 5,6-dihydro-4H-benzo[kl]acridines has been developed via Michael addition of a conjugate base of 9-methyl-3,4-dihydroacridin-1(2H)-one to various cyclic or acyclic α,β-unsaturated carbonyl/nitrile compounds under mild conditions at room temperature in a short time. To the best of our knowledge, such a general bridged annulation for the synthesis of fused N-heterocycles has not been reported in the literature.