title: Theoretical study of the mechanism of the formation of 3-unsubstituted 4,4-disubstituted beta-lactams by silver-induced ring expansion of alkoxycyclopropylamines: a new synthetic route to 4-alkoxycarbonyl-4-alkyl-2-azetidinones.
abstract: The mechanisms of formation of 4,4-dialkyl- and 4-alkoxycarbonyl-4-alkyl-2-azetidinones by silver-induced ring expansion of the corresponding 2,2-disubstituted N-chloro-1-hydroxycyclopropylamines were theoretically investigated by means of the B3LYP method and the PCM solvation model. The obtained results indicate that these reactions are facile two-step regioselective processes proceeding through a short-life nitrenium intermediate. The theoretical results thus predict that this synthetic strategy, which has already been used to obtain 4,4-dialkyl-2-azetidinones, could also be a new route to efficiently obtain in a regio- and stereoselective way 4-alkoxycarbonyl-4-alkyl-2-azetidinones, which are precursors of conformationally constrained amino acids.
authors.affiliation: Departamento de Química Física y Analítica, Facultad de Química, Universidad de Oviedo, C/Julián Clavería, 8, 33006 Oviedo, Principado de Asturias, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Campomanes
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Menéndez
authors.forename: Tomás L
authors.initials: TL
authors.lastname: Sordo
mesh_terms: D003521:Cyclopropanes / Q000737:chemistry*; D007202:Indicators and Reagents; D008958:Models, Molecular; D008968:Molecular Conformation; D012834:Silver; D013816:Thermodynamics; D047090:beta-Lactams / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D003521:Cyclopropanes; D007202:Indicators and Reagents; D047090:beta-Lactams; D012834:Silver; C067351:cyclopropylamine