440 microliters of bromoform were added at -5° C. to a mixture of 4.26 mg of lithium bromide, 598 mg of potassium hydroxide and 5 ml of water and then, a solution of 825 mg of a 4-cyano-2,3-bis-[(2-methoxy-ethoxy)-methoxy]-benzaldehyde (preparation given hereafter) in 5 ml of dioxane was added dropwise. The mixture was stirred for 72 hours at 0° C. to -5° C. and was poured into a stirred mixture at 0° C. to -5° C. of 15 ml of ethyl acetate and 11 ml of hydrochloric acid. Extraction was carried out with ethyl acetate and the extracts were washed, dried and evaporated to dryness under reduced pressure. The oil obtained was used as is for the following step.
