Process for preparing unsaturated ketones

A process for preparing unsaturated ketones of the general formula I

• in which the dotted line can be an additional C—C bond, R1 is an alkyl group with 1 or 2 C atoms, and R2 is an alkyl group with 1 to 4 C atoms, by reacting α,β-unsaturated alcohols of the general formula II
• with alkyl acetoacetates of the general formula III
• in which R3 is an alkyl group with 1 to 4 C atoms, in the presence of from 0.1 to 5 mol %, based on the alkyl acetoacetate to be reacted, of an organic aluminum compound as catalyst with elimination and continuous removal by distillation of the alcohol which is eliminated from the alkyl acetoacetate during the reaction and has the general formula IV
• R3—OH (IV)
• in a reactor system with a fitted fractionation column, wherein
• A an α,β-unsaturated alcohol which boils below 140° C. is introduced, in the absence of effective amounts of a solvent, together with the organic aluminum compound into the reaction vessel,
• B a reaction temperature which is as constant as possible between 170° C. and 250° C. is set under elevated pressure,
• C at this temperature, the alkyl acetoacetate is metered into the mixture, obtained in A, of the α,β-unsaturated alcohol and the organic aluminum compound, and
• D during the reaction the content of alkyl acetoacetate in the reaction mixture is set at a value which is as constant as possible between 0.1 and 10% by weight.