Chiral (thio)phosphorodiamides as excellent hydrogen bond donor catalysts in the asymmetric Michael addition of 2-hydroxy-1,4-naphthoquione to nitroolefins
A novel type of bidentate hydrogenbonddonor catalysts based on (thio)phosphorodiamides catalophore has been developed for the asymmetric Michael addition of 2-hydroxy-1,4-naphthoquione to nitroolefins, affording the corresponding adducts in high yields with excellent level of enantioselectivities (97- >99% ee).
Continuous Flow, Highly Enantioselective Michael Additions Catalyzed by a PS-Supported Squaramide
作者:Pinar Kasaplar、Carles Rodríguez-Escrich、Miquel A. Pericàs
DOI:10.1021/ol400974z
日期:2013.7.19
A polystyrene (PS) supported bifunctional squaramide organocatalyst promotes fast Michael addition of 2-hydroxy-1,4-naphthoquinone to nitroalkenes with very high enantioselectivities at low catalyst loadings. The polystyrene supported catalyst can be recycled up to 10 times without any decrease in enantioselectivity (average 96% ee) and adapted to continuous flow operation (24 h). A single flow experiment involving six different nitroalkenes in a sequential manner highlights the applicability of this methodology for rapid access to chemical diversity.