Regio- and Stereocontrolled Palladium- or Iridium-Catalyzed Allylation

Hideto Miyabe; Yoshiji Takemoto

doi:10.1055/s-2005-869871

ACCOUNT

Regio- and Stereocontrolled Palladium- or Iridium-Catalyzed Allylation

Hideto Miyabe, Yoshiji Takemoto*
Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
Fax: +81(75)7534569; e-Mail: takemoto@pharm.kyoto-u.ac.jp;

Abstract

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Abstract

We studied palladium- or iridium-catalyzed allylation as an effective method for the asymmetric synthesis of α-amino acids, hydroxylamines, oximes, and amines. The stereochemistry of the palladium-catalyzed allylic alkylation of a prochiral diphenylimino glycinate was controlled by chiral PTC, and gave chiral amino acids. In contrast, iridium-catalyzed allylic substitution of diphenylimino glycinate proceeded with good enantio- and diastereoselectivities with a new bidentate chiral ligand to give a novel method for preparing two branched diastereoisomers by simply switching the base. For the synthesis of α,α-disubstituted amino acids, the palladium-catalyzed tandem reaction of dehydroamino acids was developed based on radical chemistry. Next, the viability of oximes and hydroxylamines as oxygen atom nucleophiles in transition metal-catalyzed allylic substitutions was examined. Regio- and enantioselective allylic substitution of oximes and hydroxylamines was achieved by using the iridium complex of chiral pybox ligand. Sequential allylic amination gave a novel method for preparing azacycles. Finally, umpolung allylation with aldehyde or imine was studied by using palladium catalyst and indium iodide. The palladium-indium iodide-mediated reaction of chiral 2-vinylaziridines with aldehydride proceeded with excellent diastereoselectivity. The role of water in directing the diastereo- or regioselectivities was investigated in the allylation and propargylation of chiral oxime ether. The allylation of oxime ether with monosubstituted allylic reagents afforded either γ-adduct or α-adduct depending on the reaction conditions.

1 Introduction

2 Allylic Substitution with Carbon Nucleophile

2.1 Stereocontrol in Palladium-Catalyzed Reaction of Glycinate

2.2 Stereocontrol in Iridium-Catalyzed Reaction of Glycinate

2.3 Tandem Carbon-Carbon Bond-Forming Reaction of Dehydroamino Acids

3 Allylic Substitution with a Heteroatom Nucleophile

3.1 Reactivity of Oxygen Atom Nucleophile

3.2 Stereocontrol in Iridium-Catalyzed Reaction

3.3 Iridium-Catalyzed Sequential Allylic Substitution

4 Palladium and Indium Iodide-Mediated Reaction

4.1 Reaction of Chiral 2-Vinylaziridines

4.2 Diastereo- and Regioselectivities in Allylation of Imines

4.3 Propargylation of Glyoxylic Oxime Ether

5 Conclusion

Key words

allylic substitution - palladium - iridium - indium iodide - regioselective - enantioselective - amino acid

Full Text

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