38154-43-7Relevant academic research and scientific papers
Synthesis and post-resolution modification of new axially chiral ligands for asymmetric catalysis
Fleming, William J.,Mueller-Bunz, Helge,Guiry, Patrick J.
experimental part, p. 5996 - 6004 (2011/03/17)
The synthesis of four new members of the Quinazolinap series of ligands is described. Three of these ligands were prepared by post-resolution modification of the known ligand (R)-7-chloro-2-isopropyl-Quinazolinap, a new approach which offers an expedient route to a range of enantiopure ligands as it precludes the need for resolution of each ligand prepared. The remaining ligand, 7-chloro-2-methyl-Quinazolinap, was prepared in a seven-step synthetic sequence incorporating palladium- and nickel-catalyzed transformations as the key steps. A diastereomerically pure palladacycle of this ligand was characterised by X-ray crystallography. (R)-7-Chloro-2-isopropyl-Quinazolinap was applied to the rhodium-catalyzed hydroboration of vinylarenes with regioselectivities of up to > 99:1 and ee values of up to 68%. Each of the Quinazolinap ligands prepared were applied to the palladium-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate resulting in conversions of up to 100% and ee values of up to 85%. Solution-phase NMR studies on a palladium complex of one of the ligands provided a rationale for the sense of asymmetric induction. Foue new members of the Quinazolinap series of ligands are prepared, three by post-resolution modification. They were applied to the rhodium-catalyzed hydroboration of vinylarenes with regioselectivities of catalyzed allylic of up to >99:1 and ee values of up to 68%. Each of the Quinazolinap ligands prepared were applied to the palladium-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate in a synthetic and mechanistic study which helped to rationalize the sense of asymmetric induction observed.
