Process for the manufacture of cyclohexane-1,3-diones and 6-alkyl-3,4-dihydro-2-pyranones

摘要

Cyclohexane-1,3-diones of the formula <IMAGE> having up to 24 carbon atoms are prepared in admixture with 6-alkyl-3,4-dihydro-2-pyranones of the formula <IMAGE> having up to 24 carbon atoms, in which formulae the radicals R and R' may be identical or different and represent each a hydrogen atom, an alkyl, a cycloalkyl or an aryl group each having up to 12 carbon atoms and the two radicals R' together optionally represent a -(CH2)3-group, by passing 4-oxocarboxylic acids of the formula <IMAGE> having up to 24 carbon atoms and in which R and R' have the above meaning at a temperature of from 250 DEG to 500 DEG C in the gaseous phase over a dehydration catalyst and the pyranones are converted into cyclohexane-1,3-diones by passing them in the gaseous phase over a dehydration catalyst at a temperature of from 250 DEG to 500 DEG C.