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
Direct α-hydroxylation of ketones using molecular oxygen was accomplished by organic–inorganic hybrid polymers. A newly prepared Cu-piperazine hybrid polymer was tolerant to the basic conditions, and with employment of lithium hydroxide smoothly catalyzed the α-hydroxylation of ketones. In the present catalytic process not only tetralone derivatives, but also acyclic ketones were converted to the α-hydroxy ketones in good yield.
strategy for the encapsulation of magneticnanobeads was developed by using the in situ self-assembly of an organic-inorganichybrid polymer. The hybrid polymer of [Cu(bpy)(BF(4))(2)(H(2)O)(2)](bpy)}(n) (bpy=4,4'-bipyridine) was constructed on the surface of amino-functionalized magnetic beads and the resulting hybrid-polymer-encapsulated beads were utilized as catalysts for the oxidation of silyl enolates
Herein is disclosed an efficient catalyticenantioselective protonation of enol acetates by means of a readily implementable transition-metal-free chemical process. By making use of simple hygrogenocarbonates as the proton source and hydroquinine anthraquinone-1,4-diyl diether as the chiral proton shuttle, a series of cyclic enol trifluoroacetates are protonated under mild conditions to yield the corresponding
The combination of cinchona alkaloids and carboxylic acids provides a very simple chiral proton source. By using this system, enantioselectiveprotonation of silylenolates was achieved affording the corresponding ketones in high yields and in up to 75% ee.
金鸡纳生物碱和羧酸的组合提供了一种非常简单的手性质子源。通过使用该系统,实现了甲硅烷基烯醇化物的对映选择性质子化,以高产率和高达 75% ee 提供相应的酮。