title: Stereocontrolled Synthesis of β-Lactams within [2]Rotaxanes: Showcasing the Chemical Consequences of the Mechanical Bond.
abstract: The intramolecular cyclization of N-benzylfumaramide [2]rotaxanes is described. The mechanical bond of these substrates activates this transformation to proceed in high yields and in a regio- and diastereoselective manner, giving interlocked 3,4-disubstituted trans-azetidin-2-ones. This activation effect markedly differs from the more common shielding protection of threaded functions by the macrocycle, in this case promoting an unusual and disfavored 4-exo-trig ring closure. Kinetic and synthetic studies allowed us to delineate an advantageous approach toward β-lactams based on a two-step, one-pot protocol: an intramolecular ring closure followed by a thermally induced dethreading step. The advantages of carrying out this cyclization in the confined space of a benzylic amide macrocycle are attributed to its anchimeric assistance.
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, and ‡Sección Universitaria de Instrumentación Científica, Servicio de Apoyo a la Investigación, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , E-30100 Murcia, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Martinez-Cuezva
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, and ‡Sección Universitaria de Instrumentación Científica, Servicio de Apoyo a la Investigación, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , E-30100 Murcia, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Lopez-Leonardo
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, and ‡Sección Universitaria de Instrumentación Científica, Servicio de Apoyo a la Investigación, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , E-30100 Murcia, Spain.
authors.forename: Delia
authors.initials: D
authors.lastname: Bautista
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, and ‡Sección Universitaria de Instrumentación Científica, Servicio de Apoyo a la Investigación, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , E-30100 Murcia, Spain.
authors.forename: Mateo
authors.initials: M
authors.lastname: Alajarin
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, and ‡Sección Universitaria de Instrumentación Científica, Servicio de Apoyo a la Investigación, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia , E-30100 Murcia, Spain.
authors.forename: Jose
authors.initials: J
authors.lastname: Berna