Bulky P-stereogenic ligands. A success story in asymmetric catalysis
Pep Rojo, Antoni Riéra, Xavier Verdaguer
Abstract
Since the development of BisP* ligand by Imamoto, P-stereogenic phosphines bearing a bulky tert-butyl group and a smaller alkyl group have demonstrated extraordinary proficiency in a wide range of asymmetric processes. Over time, this class of ligands has brought about the introduction of more rigid backbones, the three-hindered quadrant concept, and the substitution of the tert-butyl group by adamantyl. The tert-butyl methyl fragment has also been introduced in phosphino-oxazoline-type ligands, and chemists in the industrial sector have also contributed to the evolution of this class of ligands by reporting the first successful P-stereogenic Buchwald-type monophosphines for asymmetric coupling reactions. The present review covers the synthesis and applications of bulky P-stereogenic phosphines that have been developed since the advent of BisP* in the late 1990s, with a special emphasis on ligands that have been successfully applied in asymmetric catalysis.