Polymer-supported L-prolinol-based catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinyl)imines

L.-Prolinol-based ligands anchored to Merrifield or Wang-type resins have been shown to form efficient catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinyl)imines. The enantioselectivity achieved with the polymeric catalyst (ee up to 88%) is slightly lower than the one obtained with the homogeneous ligand N-benzyl-L-prolinol, but the polymer-supported ligand presents the advantage of its recyclability: it can be recovered and used in up to six consecutive catalytic cycles with only a slight decrease in the enantiomeric excess. The phosphinamides obtained as addition products can be transformed into the corresponding enantiomerically enriched alpha-branched primary amines under mild acidic conditions. (C) 2012 Elsevier Ltd. All rights reserved.