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1.1.13 Carbene-Catalyzed Benzoin Reactions

DOI: 10.1055/sos-SD-204-00276

Suzuki, K.; Takikawa, H.Science of Synthesis: Asymmetric Organocatalysis, (20121591.

General Introduction

N-Heterocyclic carbenes (NHCs) are singlet species stabilized by heteroatoms including at least one nitrogen. The lone-pair electrons of the heteroatom are delocalized onto the carbene center to form an ylide as a resonance structure. In addition to their role as excellent ligands for transition metals, there is also increasing interest in the role of N-heterocyclic carbenes as organocatalysts. Among numerous N-heterocyclic carbenes in organocatalysis, four types are representative, i.e. imidazolidin-4-ylidene, 1H-imidazol-5(4H)-ylidene, 1H-1,2,4-triazol-5(4H)-ylidene, and thiazol-2(3H)-ylidene (Scheme 1).

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