Abstract
Luminescence-decay measurements in combination with high-performance liquid chromatography analyses were used to study the relationship between rates of catalysis and water-coordination numbers of europium-based precatalysts in the aqueous Mukaiyama aldol reaction. A correlation between reactivity and water-coordination number was observed and is reported here.
Highlights
Some of the most important transformations in organic chemistry result in the formation of carbon–carbon and carbon–heteroatom bonds, and both of these bonds can be formed using lanthanide triflate [Ln(OTf)3]-containing precatalysts [1,2,3,4,5,6,7,8,9,10,11,12,13,14]
We have reported the dynamic luminescence-decay measurements of Eu(NO3)3 and Eu(OTf)3 in binary solvent mixtures
In addition to monitoring the water-coordination numbers of these europium-containing precatalysts, we measured the yields and steady state reaction rates of the Mukaiyama aldol reaction catalyzed by these salts in solvent mixtures from 1 to 40% H2O in THF
Summary
Carbon and carbon–heteroatom bonds, and both of these bonds can be formed using lanthanide triflate [Ln(OTf)3]-containing precatalysts [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. The Lewis-acidic and water-tolerant features of lanthanide(III) salts have aroused much interest in aqueous lanthanide-catalyzed bond-forming reactions [1,2,3,4,5,6]. We are studying the Mukaiyama aldol reaction between a silyl enol ether and an aldehyde because this reaction can be both water-tolerant and stereoselective, making it an important carbon–carbon bond-forming reaction (Figure 1) [3,4,15,16]. We hypothesized that the water-coordination numbers of lanthanide-based precatalysts influenced the reaction rate and final yield of this reaction. We contribute to the mechanistic understanding of the aqueous lanthanide-catalyzed Mukaiyama aldol reaction by correlating the water-coordination numbers of europium-based precatalysts with steady state reaction rates. We describe the influence of europium counteranions on reaction yields and steady state reaction rates
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