Dimethylformamide → 2-(1-Methylbutyloxy)-3-dimethylaminoacrolein

A solution prepared by adding 30 g of dried N,N-dimethylformamide to dried dichloroethane was cooled to 5° C. or lower, After a solution containing 63 g of phosphorus oxychlorate dissolved in dichloroethane was added to the cooled solution dropwise, the mixture was stirred for 30 minutes at 5° C. or lower. Subsequently, to the reaction solution was added a dichloroethane solution of the compound (54), and the resulting mixture was stirred for 30 minutes at room temperature and then for one hour at 70° C. After the reaction solution was cooled to room temperature, the reaction solution was poured into ice water and was then made basic by addition of potassium carbonate. The reaction solution was then concentrated under reduced pressure. The concentrate was warmed and stirred, and was then extracted with ethyl acetate. After the extract was dried over magnesium sulfate, the solvent used was distilled out. The residue was distilled under reduced pressure to obtain 2-(1-methylbutyloxy)-3-dimethylaminoacrolein (55) (boiling point: 150° to 155° C./5 mmHg).