A dramatic switch of enantioselectivity in asymmetric heck reaction by benzylic substituents of ligands.
A series of benzylic substituted P, N-ligands 1 and 2 have been synthesized. The Pd-complexes of these ligands show high catalytic activity and enantioselectivity in catalyzing the asymmetric Heck reaction. A dramatic switch in enantioselectivity is realized using ligands with and without substituents at the benzylic position of the ligand. Ligands 1 with H as the substituents offer products in (R)-configuration while ligands 2 with the methyl as substituents result in (S)-configuration products. In most cases high enantioselectivities are achieved. Density functional theory calculations on the reaction mechanism as well as X-ray analysis of 1a-PdCl 2 and 2a-PdCl 2 complexes provide a rational explanation for the above observations.
Wu
Wen-Qiong
WQ
Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Feng Lin Road, Shanghai, 200032, China.
Peng
Qian
Q
Dong
Da-Xuan
DX
Hou
Xue-Long
XL
Wu
Yun-Dong
YD
D001593:Benzyl Compounds / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D005663:Furans / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D010165:Palladium / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry; D012825:Silicon / Q000737:chemistry; D013237:Stereoisomerism
D001593:Benzyl Compounds; D005663:Furans; D008024:Ligands; D011758:Pyrroles; C073812:2,3-dihydrofuran; D010165:Palladium; D012211:Rhenium; D012825:Silicon