Stereoselective synthesis and functionalization of 4-heterosubstituted β-lactams

Polyfunctionalized β-lactams were prepared with high stereoselectivity in an efficient manner. A palladium-catalyzed [2+2] carbonylative cycloaddition of allyl bromide with heteroaryliden-anilines afforded 2-azetidinones N-phenyl substituted, with an heteroaryl moiety linked at the C-4 carbon, and an alkenyl group at the C-3 carbon. The C-3 and the C-4 positions could be further functionalized inserting alkyl and hydroxyl groups in the azetidinone ring, through the generation of a stable azetidinyl anion then captured by various electrophiles.