Structures and Ambident Reactivities of Azolium Enolates


  • We thank the Deutsche Forschungsgemeinschaft (SFB 749, project B1) for financial support, Dr. P. Mayer for the determination of the X-ray structures, and Dr. K. Troshin, Dr. D. S. Stephenson, Dr. J. Ammer, Dr. A. R. Ofial, and the members of COST action CM0905 “Organocatalysis” for helpful discussions. We are grateful to Prof. L. Delaude (Univ. Liége) for kindly providing a preprint of Ref. [12c].


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Oxygen versus carbon: Azolium enolates were generated by the reactions of N-heterocyclic carbenes (NHCs) with methyl phenyl ketene and characterized by X-ray crystallography. Kinetic studies show that the enolate oxygen is 20 times more nucleophilic than the carbon atom, but under thermodynamic control exclusive C-addition products were formed.