title: Base-Catalyzed Asymmetric α-Functionalization of 2-(Cyanomethyl)azaarene N-Oxides Leading to Quaternary Stereocenters.
abstract: A simple, new strategy for the direct asymmetric α-functionalization of 2-alkyl azaarenes is described. Specifically, a Brønsted base catalyzed conjugate addition of substituted 2-cyanomethylpyridine (and pyrazine) N-oxides to acrylate equivalents to afford hitherto elusive 2-tert-alkyl azaaryl adducts with high enantioselectivity (up to 94% ee) is realized. Extension of the method to the α-amination reaction by using azodicarboxylate esters as electrophiles is also demonstrated. Key for success is the N-oxide functionality of substrates that acts as a removable activating and stereodirecting group. A bifunctional Brønsted base catalyst bearing a squaramide with an attached bulky silyl group is also disclosed.
authors.affiliation: Departamento de Química Orgánica I, Universidad del País Vasco , Manuel Lardizábal 3, 20018-San Sebastián, Spain.
authors.forename: Joseba
authors.initials: J
authors.lastname: Izquierdo
authors.affiliation: Departamento de Química Orgánica I, Universidad del País Vasco , Manuel Lardizábal 3, 20018-San Sebastián, Spain.
authors.forename: Aitor
authors.initials: A
authors.lastname: Landa
authors.affiliation: Departamento de Química Orgánica I, Universidad del País Vasco , Manuel Lardizábal 3, 20018-San Sebastián, Spain.
authors.forename: Iñaki
authors.initials: I
authors.lastname: Bastida
authors.affiliation: Departamento de Química Orgánica I, Universidad del País Vasco , Manuel Lardizábal 3, 20018-San Sebastián, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: López
authors.affiliation: Departamento de Química Orgánica I, Universidad del País Vasco , Manuel Lardizábal 3, 20018-San Sebastián, Spain.
authors.forename: Mikel
authors.initials: M
authors.lastname: Oiarbide
authors.affiliation: Departamento de Química Orgánica I, Universidad del País Vasco , Manuel Lardizábal 3, 20018-San Sebastián, Spain.
authors.forename: Claudio
authors.initials: C
authors.lastname: Palomo