Patent ID: 8791276

Claim:
A process for the preparation of 2-substituted 4-hydroxy-4-methyltetrahydropyrans of the formula (I) where the radical R 1 is a straight-chain or branched alkyl or alkenyl radical having 1 to 12 carbon atoms, an optionally alkyl-substituted cycloalkyl radical having in total 3 to 12 carbon atoms or an optionally alkyl- and/or alkoxy-substituted aryl radical having in total 6 to 12 carbon atoms, which comprises reacting 3-methylbut-3-en-1-ol of the formula (II) with an aldehyde of the formula (III) R 1 —CHO (III), where the radical R 1 has the same meaning as in formula (I) and where the reaction is carried out in the presence of at least 10 mol % water, wherein the amount of water is based on the amount of 3-methylbut-3-en-1-ol of the formula (II) if the 3-methylbut-3-en-1-ol is used in deficit or to the amount of aldehyde of the formula (III) if used in deficit or, in the case of equimolar reaction of the two starting materials, to the quantitative amount of one of the two, and in the presence of a strongly acidic cation exchanger, and then the distillative separation is carried out in a dividing wall column or in an interconnection of at least two distillation columns in the form of a thermal coupling and one or more side take-off points at an absolute operating pressure of up to 500 mbar.