PURPOSE: To profitably prepare the subject compound through the processes comprising the hydroformylation of 2,7-octadiene-1-ol under a specific condition, the extraction of the intermediate products, the re-cyclization of the remained solution, the hydrogenation of the extracted solution, the distillation of the hydrogenated products and the re-cyclization of useful components.

CONSTITUTION: (i) 2,7-Octadiene-1-ol is subjected to a hydroformylation reaction using a mixture gas comprising CO and H2 in the presence of a rhodium complex compound, a specific water-soluble mono-coordinating phosphine and a specified water-soluble coordinating phosphine in a sulfolane aqueous solution. (ii) 9-Hydroxy-7-nonene-1-al(HNEL) is extracted from the reaction mixture with the mixture of a 5-11C saturated aliphatic primary alcohol and a 5-10C saturated aliphatic hydrocarbon. (iii) The extraction residue containing the catalyst component is returned to the process and (iv) the extraction solution containing HNEL is hydrogenated. (v) The reaction mixture is, if necessary, washed with water and distilled, and (vi) the recovered sulfolane is returned to the process, thereby continuously providing the subject compound in high selectivity and purity.