Abstract
This review focuses on the applications of multicenter organocatalysts,
which can form chiral hydrogen bonded networks. The high tunabilities
of these catalysts in terms of their active sites, chiral spacers,
and tolerated reaction conditions have been used advantageously
in applications to various classes of catalytic asymmetric carbon-carbon
and carbon-oxygen bond forming reactions. The high stereoselectivities
of these reactions are attributed to the chemoselective dual activation
of both the nucleophile and electrophile reacting partners in asymmetric
space. The key requirements for the cooperative effects of weak
noncovalent-bonding interactions are discussed.
1 Introduction
2 General Concept for the Design of Chiral Hydrogen Bonding
Networks
3 Bis-thiourea-type Homo-bifunctional Organocatalysts
3.1 Enantioselective Morita-Baylis-Hillman
Reaction
4 Guanidinium-Thiourea Hetero-multifunctional Organocatalysts
4.1 Catalytic Diastereo- and Enantioselective Nitroaldol Reaction
of Prochiral Aldehydes
4.2 Catalytic Diastereoselective Nitroaldol Reaction of
4.3 Catalytic Asymmetric Nitroaldol Reaction of α-Keto
Esters
4.4 Catalytic Asymmetric Nitro-Mannich-type Reaction
4.5 Catalytic Asymmetric Mannich-type Reaction with Malonates
5 Guanidinium-Urea Hetero-multifunctional Organocatalysts
5.1 Catalytic Asymmetric Epoxidation with Hydrogen Peroxide
6 Summary
Key words
asymmetric synthesis - catalysis - guanidinium - thiourea - urea
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