Strategies for Constructing Diverse Chiral Environments in Multimetallic Bifunctional Asymmetric Catalysis

Abstract

Recent advances from our group in the design and applications of multimetallic bifunctional asymmetric catalysts are described. Suitable design of chiral ligands and selection of metals were important to realize cooperative bimetallic catalysis. In this account, our strategies for constructing flexible and diverse chiral environments in multimetallic complexes for the rapid optimization of targeted reactions, such as tertiary nitroaldol kinetic resolution, cyclopropanation of electron-deficient olefins, cyano-ethoxycarbonylation of aldehydes, direct Mannich-type reactions, the nitro-Mannich reaction, the anti-selective nitroaldol reaction, and amination, are discussed in detail.

1 Introduction

2 Heterobimetallic Rare-Earth-Alkali Metal-BINOL Complexes

2.1 Background

2.2 Catalytic Kinetic Resolution of Tertiary Nitroaldols

2.3 Catalytic Asymmetric Cyclopropanation of Enones

2.4 Catalytic Asymmetric Cyano-ethoxycarbonylation

3 La Aryloxide/Li Aryloxide/pybox Complexes for Direct Catalytic Asymmetric Mannich-type Reactions

4 Heterobimetallic Transition Metal/Rare-Earth Metal/Dinucleating Schiff Base Complexes

4.1 syn-Selective Nitro-Mannich-type Reaction

4.2 anti-Selective Nitroaldol Reaction

5 Homobimetallic Nickel/Dinucleating Schiff Base Complex

6 Rare-Earth Metal/Amide Complexes for Catalytic Asymmetric Amination

7 Summary

Key words

asymmetric catalysis - asymmetric synthesis - bifunctional catalysis - rare-earth metals - Lewis acids

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• 70b

  Mashiko T., Kumagai N., Shibasaki M.; manuscript in preparation.

29

A related, dual control mechanism has been proposed by MacMillan, see reference 24a. See also, reference 10b for a related mechanism.

30

Coordination of a seventh ligand, such as H₂O, to the rare-earth-metal center was observed for rare-earth metals with a relatively large ionic radius, such as La, Pr, Eu; see references 8b, 8c, and 8e. Salvadori and co-workers reported different properties for Yb complexes; see reference 8d.

50

Trichloromethyl carbinols were stereoselectively converted into azetidinecarboxylic acids; see reference 47.