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

Abstract

1H-Pyrrole and lactone-type 2,3-furandione derivatives were reacted in anhydrous diethyl ether (Et2O) at room temperature, and then one of the important alkaloid skeletons, pyrrolizinone derivatives, were synthesized via a single step and catalyst-free approach. Various pyrrolizinone derivatives having various substituents such as phenyl, substituted phenyl, thiophene, -CF3, naphthalene, bi-phenyl, ester, and oxalate were yielded. Employing an equimolar pyrrole molecule yielded pyrrolizinones, while using an excess molar of pyrrole yielded pyrrolizino[1,2-a]pyrrolizin-5-one which is not present in the literature. Yield of purified molecules was up to 91%. One of the cyclization processes was carried out on a gram-scale, yielding 0.952 g (71%).