Lanthanoid triisopropoxides are active catalysts for aldol reactions. Aldehydes give the corresponding β-hydroxyaldehydes at low temperatures in good yields, whereas ketones are less reactive, but form condensation products at high temperatures. Exceptionally, γ- or δ-diketones easily undergo condensation to give five- and six-membered unsaturated ketones in high yields. The lanthanoid propoxides, catalyzing the Michael addition of ketones to α,β-unsaturated ketones, which give δ-diketones, are also good catalysts for the Robinson-type annelation. In these reactions, the catalytic activity of the lanthanum propoxide is higher than those of the heavy lanthanoid propoxides, and is almost comparable to that of sodium isopropoxide. Since aluminum triisopropoxide shows poor activity, the lanthanoid propoxides are considerably basic for trivalent metal alkoxides.
A comprehensive investigation and optimisation on the proteinogenic amino acid catalysed homo aldol condensation
作者:Karoline A. Ostrowski、Dominik Lichte、Moritz Stuck、Andreas J. Vorholt
DOI:10.1016/j.tet.2015.11.069
日期:2016.2
A systematic investigation regarding the application of catalytic amounts of all 20 proteinogenic amino acids in the homo aldolcondensation of aldehydes is described obtaining excellent yields of the desired α,β-unsaturated aldehyde. These investigations proved the basic amino acids, lysine and arginine, are effective as organocatalysts, if comparably low concentrations are applied. Through the stepwise
A green method for the self-aldol condensation of aldehydes using lysine
作者:Yutaka Watanabe、Kazue Sawada、Minoru Hayashi
DOI:10.1039/b918349c
日期:——
A self-condensation of aldehydes has been conveniently accomplished by the catalytic action of lysine in water or a solvent-free system under specific emulsion conditions to give α-branched α,β-unsaturated aldehydes in good yields.
Alkenyl (or aryl) iodide (or bromide) is readily reduced with CrCl2 is N,N-dimethylformamide at 25°C to gice the corresponding organochromium species which adds selectively to an aldehyde moiety without affecting the coexisting ketone or cyano group of the substrate.