Two novel homologous [2]paracyclo[2](5,8)quinolinophane-derived P,N-bidentate planar chiral ligands have been synthesised and their effectiveness in asymmetric catalysis tested in palladium-catalysed allylic malonylation of 1,3-diphenylpropenyl acetate. The extent of asymmetric induction depends linearly on the ligand/metal molar ratio, indicating the involvement of P,P-type and chelate P,N-type pi-allylpalladium complexes in equilibrium. The length of the chain that binds the diphenylphosphine group to the quinolinophane moiety, while appreciably affecting the P,N-complex stability, has little effect on the extent of asymmetric induction, which is due to the greater reactivity of the [PN]-exo-syn-syn- ([PN](xss)) with respect to the [PN]-endo-syn-syn- ([PN](nss)) pi-allylpalladium complex.
Quinolinophane-Derived Alkyldiphenylphosphines: Two Homologous P,N-Type Planar Chiral Ligands for a Study of Palladium-Catalysed Allylic Alkylation
RUZZICONI, Renzo;SANTI, Claudio;
2007
Abstract
Two novel homologous [2]paracyclo[2](5,8)quinolinophane-derived P,N-bidentate planar chiral ligands have been synthesised and their effectiveness in asymmetric catalysis tested in palladium-catalysed allylic malonylation of 1,3-diphenylpropenyl acetate. The extent of asymmetric induction depends linearly on the ligand/metal molar ratio, indicating the involvement of P,P-type and chelate P,N-type pi-allylpalladium complexes in equilibrium. The length of the chain that binds the diphenylphosphine group to the quinolinophane moiety, while appreciably affecting the P,N-complex stability, has little effect on the extent of asymmetric induction, which is due to the greater reactivity of the [PN]-exo-syn-syn- ([PN](xss)) with respect to the [PN]-endo-syn-syn- ([PN](nss)) pi-allylpalladium complex.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
