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
