Intriguing behavior of cinchona alkaloids in the enantioselective organocatalytic hydroxyamination of alpha-substituted-alpha-cyanoacetates.
The cinchona alkaloid quinine promotes the enantioselective nitroso-aldol reaction between alpha-aryl-alpha-cyanoacetates and nitrosobenzene to give the hydroxyamination products with total chemoselectivity. Treatment of the reaction mixture with Zn/AcOH affords the corresponding amines in high yield and moderate enantioselectivity. An unusual effect on the enantioselectivity was observed with the catalyst loading and solvent. A reductive protocol allows the construction of an optically active 1,2-diamine moiety bearing a quaternary center.
Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain.
Jesús
J
López-Cantarero
M Belén
MB
Cid
Thomas B
TB
Poulsen
Marco
M
Bella
José Luis García
JL
Ruano
Karl Anker
KA
Jørgensen