Pure Appl. Chem., 2008, Vol. 80, No. 5, pp. 807-817
doi:10.1351/pac200880050807
1,4-Additions of arylboron, -silicon, and -bismuth compounds to α,β-unsaturated carbonyl compounds catalyzed by dicationic palladium(II) complexes*
Yasunori Yamamoto1, Takashi Nishikata2, and Norio Miyaura1
1Division of Chemical Process Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan; 2Innovation Plaza Hokkaido, Japan Science and Technology Agency, Sapporo 060-0819, Japan
Abstract:
An enantioselective synthesis of cyclic and acyclic β-aryl ketone and aldehydes via Pd(II)-catalyzed 1,4-addition of Ar-m [m = B(OH)2, BF3K, Si(OMe)3, SiF3, BiAr2] to α,β-unsaturated ketones or aldehydes is described. The catalytic cycle involves transmetallation between Ar-m and Pd complexes as a key process, the mechanism of which is discussed on the basis of characterization of the transmetallation intermediate and electronic effect of the substituents. The enantioselection mechanism and efficiency of a chiraphos ligand for structurally planar α,β-unsaturated ketones are discussed on the basis of the X-ray structure of the catalyst and results of density functional theory (DFT) computational studies on the model of coordination of the substrates to the phenylpalladium(II)/(S,S)-chiraphos intermediate.
Keywords: arylboron compounds; asymmetric 1,4-addition; dicationic Pd catalyst; enantioselection mechanism; transmetallation.
*Paper based on a presentation at the 14th International Symposium on Organometallic Chemistry Directed Towards Organic Synthesis (OMCOS-14), 2-6 August 2007, Nara, Japan. Other presentations are published in this issue, pp. 807-1194.