Synthesis of Pyrrolizinone and Pyrrolizino[1,2-a]pyrrolizin-5-one Skeletons Starting From Pyrrole through a Single-Step and Catalyst-Free Approach

1H-Pyrrole reacted with lactone-type 2,3-furandione derivatives in anhydrous diethyl ether at room temperature to give a series of derivatives of pyrrolizinone (which is among the most important al-kaloid skeletons) in a single step without a catalyst. Pyrrolizinone derivatives with a variety of substituents, such as phenyl, substituted phenyl, thienyl, trifluoromethyl, naphthyl, biphenylyl, ester, or oxalate, were obtained. The reaction of an equimolar amount of pyrrole gave pyrroliz-inones, whereas an excess of pyrrole gave pyrrolizino[1,2-a]pyrrolizin-5-ones containing a skeleton that had not previously been reported. The purified molecules were obtained in yields of up to 91%. One cyclization process was carried out on a gram scale, yielding 0.952 g (71%) of the corresponding product.

Automated summary

1H-Pyrrole reacted with lactone-type 2,3-furandione derivatives in anhydrous diethyl ether at room temperature to synthesize a series of pyrrolizinone derivatives in a single step without a catalyst. Various substituents were introduced in the pyrrolizinone derivatives, such as phenyl, substituted phenyl, thienyl, trifluoromethyl, naphthyl, biphenylyl, ester, or oxalate. The reaction conditions also led to the formation of pyrrolizino[1,2-a]pyrrolizin-5-ones with a novel skeleton when an excess of pyrrole was used. The purified molecules were obtained with high yields, up to 91%, and a gram-scale reaction yielded 0.952 g (71%) of the corresponding product.