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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 substituent...

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Published in:Journal of the American Chemical Society Vol. 130; no. 30; pp. 9717 - 9726
Main Authors: Wen-Qiong Wu, Qian Peng, Da-Xuan Dong, Xue-long Hou, Yun-Dong Wu
Format: Article
Published: American Chemical Society 7/30/2008
Subjects:
Ligands (Chemistry)
Organic synthesis
Palladium
Transition metal complexes
Density functionals
Reaction mechanisms (Chemistry)
Online Access:View this record in EBSCOhost
Summary: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-PdCI and 2a-PdCl complexes provide a rational explanation for the above observations.