P-chirogenic organophosphorus acid-bases in asymmetric organocatalysis
As environmentally friendly processes are now strongly needed by the modern world, asymmetric organocatalysis has emerged as a powerful alternative method to produce chiral substances compared to catalysis with transition metal complexes and enzyme-mediated bioconversion. Although numerous classes of chiral Lewis or Brönsted acid-bases were known to be efficient in asymmetric organocatalyzed reactions, the use of phosphorus derivatives bearing the chirality on the phosphorus centre (P-chirogenic) have been less studied. The great interest of the P-chirogenic phosphorus compounds stems from their easy structural design which allows the development of a specific organocatalyst for a given asymmetric reaction. The article reviews the use of P-chirogenic organophosphorus compounds in asymmetric organocatalyzed processes.
Organocatalysis including phase-transfer catalysis has long been recognized as a versatile methodology for organic synthesis in both industrial and academic laboratories, thanks to its mild reaction conditions, inexpensive and environmentally benign reagents or solvents, and the possibility of conducting large-scale preparations (1-5). However to date, as environmentally friendly processes are now strongly needed by the modern world, the development of metal-free catalyzed reactions has received an increasing attention more particularly for the production of chiral substances for health, body-care, agriculture or nutrition. In this field, considerable advance has been made in asymmetric organocatalyzed processes using optically active acid-base promoters such as proline 1, quinine 2, thiourea 3, quaternary ammonium salt 4 or phosphoric acid 5 derivatives (1-5).
Most of these compounds own their chirality from the carbon skeleton and few studies involve organocatalysts with an asymmetric center on the Brönsted-Lewis acid-base active group. A priori o ...