Propargylation of Ugi Amide Dianion: An Entry into Pyrrolidinone and Benzoindolizidine Alkaloid Analogues

Propargylation of Ugi adducts under the addition of excess sodium hydride in DMSO leads to direct formation of pyrrolidinone enamides, which are useful precursors of iminium intermediates and may be trapped by various nucleophiles. This approach has been applied to the formation of benzoindolizidine alkaloids with high diversity via a Ugi/propargylation/Pictet-Spengler cyclization.