Novel phosphinobioxazines as chiral ligands in palladium-catalyzed enantioselective allylic substitution

Abstract

Novel C-2-symmetric chiral (4S,4'S)-bisphosphinobioxazine 2a, a six-membered analog of (4S,4S')bisphosphinobioxazoline (Phos-Biox, 1), and monophosphinobioxazine 2b have been synthesized and used as chiral ligands for Pd-catalyzed asymmetric allylic substitutions of rac-1,3-diphenyl-2-propenyl acetate with dimethyl malonate. C-2-Symmetric bisphosphinobioxazine 2a exhibited moderate enantioselectivities (63-84% ee) whereas excellent enantioselectivities (94-95% ee) were observed with monophosphinobioxazine 2b. (C) 1999 Elsevier Science Ltd. All rights reserved.