(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

摘要

Strike while the iron is hot! A BF_3-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.