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

Abstract

Abstract1H-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 alkaloid 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 pyrrolizinones, 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.