Organocatalyzed Enantioselective Protonation of Silyl Enol Ethers: Scope, Limitations, and Application to the Preparation of Enantioenriched Homoisoflavones
In the present work, enantioselective protonation of silylenolethers is reported by means of a variety of chiral nitrogen bases as catalysts, mainly derived from cinchonaalkaloids, in the presence of various protic nucleophiles as proton source. A detailed study of the most relevant reaction parameters is disclosed allowing high enantioselectivities of up to 92% ee with excellent yields to be achieved
The asymmetric protonation of silylenolates derived from tetralone, benzosuberone, and cyclohexanone has been successfully achieved by using simple and original betaine catalysts derived from Cinchona alkaloids (quinine and quinidine series) to afford the desired α-substituted ketones in high yields and moderate enantioselectivities. The ease of implementation of this approach along with the easy