A practical method was developed for the gain of potentially biologically active 4-aryl-5,8-epiminobenzo[7]annulenes using tropinone as starting material with an azabicyclo[3.2.1]octan skeleton. In an effort to improve product yield, reaction process conditions were optimized and the cascade Michael/cyclization reaction went most smoothly using tetrahydrofuran as solvent in the presence of DBU at 60°C for 10 hours. More diverse 4-aryl-5,8-epiminobenzo[7]annulenes were synthesized in good yields and structurally identified by NMR, FTIR and mass spectrometry analysis. The assembly of the heterocyclic core proceeds by a cascade Knoevenagel condensation, Michael addition and cyclocondensation sequence with a broad substrate applicability and good functional group tolerance.
Dao-Cai Wang, Yi Luo, Jian-Jun Li, Chi Zhang and Xiao-Peng Liu
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