Synthesis of chiral 1 '-substituted oxazolinylferrocenes as chiral ligands for Pd-catalyzed allylic substitution reactions

Abstract

Chiral 1-oxazolinyl-1'-(diphenylphosphino)ferro 4 and 1-oxazolinyl-1'-(phenylthio)ferrocenes 5 were prepared from 1,1'-dibromoferrocene through 1-oxazolinyl-1'-bromoferrocenes 3. The compounds 4 and 5 were employed as chiral ligands in Pd-catalyzed asymmetric allylic substitution reactions. High enantioselectivities (82-99% ee) and high yields (96-99%) were observed in the substitution reactions of 1,3-diphenylprop-2-enyl acetate and dimethyl malonate with the catalysts generated from [(pi-allyl)PdCl](2) and 4, while the use of 5 led to inferior results (20-75% ee and 25-28% yields). H-1-, (13)'C-, and P-31-NMR data are analyzed for the complexes obtained from the reactions of [(eta(3)-allyl)PdCl](2) and [(eta(3)-1,3-diphenylallyl)PdCl](2) with 4a and 4b. (C) 1999 Elsevier Science S,A. All rights reserved.