Abstract
Cheap, abundant but seldom-employed Ca(OH)2 was found to be an excellent low-loading (5–10 mol%) catalyst for Claisen-Schmidt condensation of aldehydes with methyl ketones under mild conditions. It was interesting that dilute aqueous ethanol (20 v/v%) was unexpectedly discovered to be the optimal solvent. The reaction was scalable at least to 100 mmol and calcium could be precipitated by CO2 and removed by filtration. Evaporation of solvent directly afforded the product in the excellent 96% yield with high purity, as confirmed by its 1H NMR spectrum.
Highlights
Α,β-Unsaturated ketones, including dimethylidene acetone derivatives, are important building blocks in organic synthesis, and key chemicals in many fields including perfumery, biochemistry, agriculture, food chemistry, polymer and material science, and others[1,2,3,4]
As part of our continuing cooperative research projects with industrial partners to develop green synthetic methodologies[19,20,21,22,23,24,25,26,27,28], we reported an organoselenium-catalyzed green oxidation of α,β-unsaturated ketones to prepare vinyl esters, which serve as versatile copolymers in material science[24]
We investigated the Ca(OH)2-catalyzed Claisen-Schmidt condensations to prepare α,β-unsaturated ketones
Summary
Α,β-Unsaturated ketones, including dimethylidene acetone derivatives, are important building blocks in organic synthesis, and key chemicals in many fields including perfumery, biochemistry, agriculture, food chemistry, polymer and material science, and others[1,2,3,4]. Claisen-Schmidt condensation appears to be the most practical method to prepare α,β-unsaturated ketones owing to its directness, clean procedures and accessible starting materials. Reactions performed in strong alkaline conditions are corrosive to equipment and generate unmanageable and corrosive solid waste These drawbacks have limited the large-scale application of NaOH. As part of our continuing cooperative research projects with industrial partners to develop green synthetic methodologies[19,20,21,22,23,24,25,26,27,28], we reported an organoselenium-catalyzed green oxidation of α,β-unsaturated ketones to prepare vinyl esters, which serve as versatile copolymers in material science[24].
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