title: Carbonyl allenylation/free radical cyclization sequence as a new regio- and stereocontrolled access to bi- and tricyclic beta-lactams.
abstract: A novel approach to racemic and enantiopure nonconventional fused bi- and tricyclic beta-lactams has been developed by using regio- and stereocontrolled intramolecular free radical reactions in monocyclic 2-azetidinone-tethered allenynes and haloallenes. The access to allene cyclization precursors was achieved by metal-mediated carbonyl allenylation of appropriately substituted 4-oxoazetidine-2-carbaldehydes in an aqueous environment. The tin-promoted radical cyclizations of allene-beta-lactams are totally regioselective for the central allenic carbon, providing bi- and tricyclic beta-lactams containing a seven-membered ring.
authors.affiliation: Departamento de Química Orgánica I, Facultad de Química, Universidad Complutense de Madrid, 28040 Madrid, Spain. alcaideb@quim.ucm.es
authors.forename: Benito
authors.initials: B
authors.lastname: Alcaide
authors.forename: Pedro
authors.initials: P
authors.lastname: Almendros
authors.forename: Cristina
authors.initials: C
authors.lastname: Aragoncillo
authors.forename: María C
authors.initials: MC
authors.lastname: Redondo
mesh_terms: D003500:Cyclization; D005609:Free Radicals; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009947:Organotin Compounds / Q000737:chemistry; D013237:Stereoisomerism; D014001:Tin / Q000737:chemistry; D047090:beta-Lactams / Q000138:chemical synthesis*
chemical_list: D005609:Free Radicals; D007202:Indicators and Reagents; D009947:Organotin Compounds; D047090:beta-Lactams; D014001:Tin; C030665:triphenyltin