One-pot synthesis of 5,6-disubstituted 3H-pyrrolizines organocatalyzed by piperidinium acetate

The organocatalyst, piperidinium acetate formed in situ, was utilized as an efficient catalyst for one-pot synthesis of 5,6-disubstituted 3H-pyrrolizines with halogen (Cl, Br), methoxy and ethyl ester groups. Absorption and emission spectra properties were also compared in dichloromethane, toluene, methanol, and DMSO. Electronic spectra were altered slightly by these substituents, which can be well explained by TD-DFT calculations. And the selected four orbital energies indicated that electrons transited smoothly from the pyrrolizine ring to the indole unit.