Exo- and Endocyclic Oxazolinyl−Phosphane Palladium Complexes:  Catalytic Behavior in Allylic Alkylation Processes

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The new bidentate chiral N,P-donor oxazolinyl−phosphane ligands 7 − 15 are described. Upon coordination to the palladium metal, ligands 7 − 12 gave endocyclic oxazolinyl−phosphane complexes having seven-membered rings, while ligands 13 − 15 afforded exocyclic oxazolinyl−phosphinite complexes with six-membered rings, depending on the relative C N oxazoline bond and metal ring position. Ionic palladium(II) complexes containing N,P-bidentate ligands and allyl groups (η 3 -C 3 H 5 for 16 − 22 and η 3 -1,3-Ph 2 -C 3 H 3 for 23 − 26 ) were prepared and fully characterized. X-ray structures were determined for complexes 18 and 19 . Pd catalytic systems containing ligands 7 − 15 were tested in the asymmetric allylic alkylation of the racemic substrates rac -3-acetoxy-1,3-diphenyl-1-propene ( I ) and ra c-3-acetoxy-1-cyclohexene ( III ). The endocyclic systems show better activites and selectivites (ee values up to 82%) than the exocyclic ones (ee values up to 72%) for substrate I . In particular, palladium endocyclic oxazoline−phosphinite systems containing the PCy 2 group ( 20, 21 ) give the highest activities, but the best enantioselectivities were observed for those containing PPh 2 ( 18, 19 ).