PROCESSO PARA A PREPARACAO DE CITRAL

Preparation of citral (I) comprises thermal decomposition of 3-methyl-2-buten-1-al-diprenylacetal and rearrangement of obtained intermediates cis/trans-prenyl-(methyl-butadienyl)-ether (IV) and 2,4,4-trimethyl-3-formyl-1,5-hexadiene (V). (IV) and (V) are continuously distilled off and converted into (I) before or after removal of by-product prenol. Preparation of 3,7-dimethyl-2,6-octadien-1-al (citral) of formula (I) comprises: (1) thermal decomposition of 3-methyl-2-buten-1-al-diprenylacetal of formula (II) optionally in the presence of an acid catalyst to split off 3-methyl-buten-1-ol (prenol) of formula (III) and form cis/trans-prenyl-(methyl-butadienyl)-ether of formula (IV); (2) Claisen rearrangement of (IV) to give 2,4,4-trimethyl-3-formyl-1,5-hexadiene of formula (V); and (3) Cope rearrangement of (V) to form (I). The transitionally formed (IV) and (V) and the desired citral as well as the prenol (III) are continuously distilled out of the reaction mixture and (IV) and (V), before or after distillative separation of (III) and optional by-products, are subjected to rearrangement to form (I) at 100-200 degrees C.