The preparation and resolution of 2-phenyl-Quinazolinap, a new atropisomeric phosphinamine ligand for asymmetric catalysis

Abstract

The preparation and resolution of an axially chiral quinazoline-containing phosphinamine ligand is described. The biaryl linkage was formed in a Pd-catalysed coupling of 4-chloro-2-phenylquinazoline 10 with 2-methoxy-1-naphthylboronic acid 11. Demethylation of the product ether 12 afforded alcohol 13 which was converted into the corresponding triflate 14 by treatment with trifluoromethanesulphonic anhydride. An Ni-catalysed phosphinylation gave the required phosphinamine ligand 9 as a racemate. Diastereomeric palladacycles 16, formed from 9 and (+)-di-μ-chlorobis[( R)-dimethyl(1-(1-naphthyl)ethyl)aminato-C 2, N]dipalladium(II) 15 were separated to give diastereomerically pure materials. An X-ray crystal structure of the ( R, R)- 16 palladacycle was determined and is discussed. Displacement of the resolving agent by reaction with 1,2-bis(diphenylphosphino)ethane gave enantiopure 2-phenyl-Quinazolinap 9, a new atropisomeric phosphinamine ligand for asymmetric catalysis.