Synthesis of 4-allenyl and 4-proparyl-2-azetidinone via Zn-mediated Barbier-type reaction and Pt-catalyzed intramolecular amidation to carbapenem skeletons

4-Propargyl-2-azetidinone and 4-allenyl-2-azetidinone derivatives can be facilely obtained from 4-acetoxy-2-azetidinone and propargyl bromides via zinc-mediated Barbier-type reaction. A new method has been developed to construct the carbapenem bicyclic nucleus by cyclization of 4-propargyl-2-azetidinone and 4-allenyl-2-azetidinone derivatives catalyzed by PtCl2.