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Methods have been developed for the synthesis of (2E)-1,1-dimethoxyalk-2-en-4-ols and (2E)-4-hydroxyalk-2-enals by reaction of (2E)-4,4-dimethoxybut-2-enals and Grignard compounds. Thermal isomerization of (2E)-4-hydroxyalk-2-enals gave the corresponding 2-alkylfurans. † Deceased.(2E)-4,4-Dimethoxybut-2-enal (I) molecule possesses a double bond and an aldehyde group, so that compound I is quite promising as polyfunctional synthon for the design of various organic compounds. It is widely used in the synthesis of a number of lowmolecular weight bioregulators such as pheromones [1], cyclohexane analogs of prostaglandins [2], maytansinoids (macrocyclic lactams exhibiting antitumor, antimyotic, and antifungal activity) [3], cephalosporin analogs [4], etc.In continuation of studies in this field, the goal of the present work was to synthesize from 4,4-dimethoxybut-2-enal (I) (2E)-4-hydroxyalk-2-enals which can be converted into cyclopentenone derivatives (intermediate compounds in the synthesis of prostaglandins [5]) via aldol condensation.The reaction of aldehyde I with alkylmagnesium bromides IIa-IId in diethyl ether at 0°C resulted in the formation of unsaturated hydroxy aldehydes IIIa-IIId in 39-50% yield (Scheme 1). (2E)-4-Hydroxynon-2-enal (IIId) is a lipid metabolite which was isolated from the red marine alga Liagora farinosa Lamouroux [6]. Using the reaction with propylmagnesium bromide (IIb) as model process we examined the effect of different factors, such as reaction temperature, workup procedure, and order of mixing of the reactants, on the reaction course. The reaction occurred at a temperature below 0°C. Addition of aldehyde I to propylmagnesium bromide (IIb) at -55 to 0°C did not change the reaction pattern to an appreciable extent. The same products were formed when the reactants were mixed in the reverse order.Intermediate organomagnesium complex was decomposed by treatment with a dilute solution of p-toluenesulfonic or hydrochloric acid or with water. In the first case, hydroxy aldehyde IIIb was the only product, regardless of the acid nature. When the mixture was treated with water at room temperature and then distilled over potassium carbonate, dimethoxy alcohol IVa may be obtained as the major product. Further experiments showed that pH value (5-6) is not a significant factor that could affect the process. The acetal protection was conserved, and dimethoxy alcohol IVb was formed if the reaction mixture was treated with an acid at -30°C (Scheme 2).Compounds IIIa-IIId were isolated by distillation or column chromatography on silica gel (eluent hex-

A procedure was developed for preparative synthesis of (Z )-5-decenyl acetate, the sex hormone of Agrotis Segetum.

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