title: The photochemical reaction of vinylaziridines and vinylazetidines with chromium(0) and molybdenum(0) (Fischer) carbene complexes.
abstract: The [5+2] and [6+2] cycloaddition reactions of vinylaziridines and vinylazetidines with ketenes generated photochemically from chromium(0) and molybdenum(0) Fischer carbene complexes have been investigated. These processes constitute a straightforward and efficient route to azepanones and azocinones, respectively. The peculiar electronic properties of the metalated ketenes allow for the introduction of electron-rich substituents in the final cycloadducts, a difficult task using conventional organic chemistry procedures. The versatility of the process is demonstrated by using Cr(0) Fischer bis(carbene) complexes as metalated bis(ketene) precursors. These species produce tethered bis(azepanone)s in a single step under mild reaction conditions. Density functional theory calculations point to a stepwise reaction pathway through the initial nucleophilic attack of the nitrogen atom of the aziridine on the metalated ketene, followed by ring closure of the zwitterionic intermediate formed.
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Universidad Complutense, 28040 Madrid (Spain), Fax: (+34) 913944310.
authors.forename: Alexandra R
authors.initials: AR
authors.lastname: Rivero
authors.forename: Israel
authors.initials: I
authors.lastname: Fernández
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Sierra
keywords: DFT calculations; aziridines; cycloaddition; metal-carbenes; photochemistry