Abstract: Method for preparing a ?-hydroxyketone having 4 to 8 carbon atoms by reacting formaldehyde with a branched or unbranched dialkyl ketone having 3 to 7 carbon atoms in the liquid phase in a reactor in the presence of a basic component at a temperature of 50 to 150° C. and a pressure of 0.2 to 10 MPa abs, in which (a) a trialkylamine having 1 to 4 carbon atoms per alkyl group is used as basic component and the reaction (b) is carried out in the presence of 1 to 25% by weight water, based on the liquid phase, and (c) at a molar ratio of trialkylamine to formaldehyde in the liquid phase of from 1 to 5.

Abstract: Method for preparing 1-hydroxy-2-methyl-3-pentanone (I) by reacting formaldehyde with diethyl ketone in a reactor in the presence of water and a basic component at a temperature of 50 to 150° C. and a pressure of 0.2 to 10 MPa abs, in which the basic component used is a trialkylamine from the group comprising trimethylamine, N,N-dimethylethylamine, N,N-diethylmethylamine, triethylamine, N,N-dimethyl-n-propylamine, N-ethyl-N-methyl-n-propylamine, N,N-dimethylisopropylamine, N-ethyl-N-methylisopropylamine, N,N-dimethyl-n-butylamine, N,N-dimethylisobutylamine and N,N-dimethyl-sec-butylamine, and from the reaction mixture obtained, trialkylamine as low boiler and a bottom product comprising 1-hydroxy-2-methyl-3-pentanone (I) as high boiler are separated in a distillation apparatus, wherein the distillation apparatus is operated at a top pressure of 0.2 to 1 MPa abs.