(1‐Alkynyl)dicarbonylcyclopentadienyliron Complexes as Electron‐Rich Alkynes in Organic Synthesis: BF3‐Mediated [2+2] Cycloaddition/Ring‐Opening Providing (2‐Alkenyl‐1‐imino)iron Complexes

Strike while the iron is hot! A BF3-mediated formal [2+2] cycloaddition between (1-alkynyl)iron complexes and aromatic aldehyde imines occurs, which is followed by ring-opening of the initially formed azacyclobutenes to yield (2-alkenyl-1-imino)iron complexes (see scheme). The resulting iron complexes undergo deferric substitution reactions with water under oxidative conditions to afford the corresponding cinnamamides with high E selectivity.