| 摘要 |
Acylals of formula (I): (where R1 and R2 are 1-4 C alkyl), e.g. trans-3-methyl-2-butene-1,4-dial-1-ylidene diacetate, are new cpds. which are prepd. by oxidizing cpds. of formula (II) with selenium dioxide in glacial acetic acid, an ether of b.pt. 80-170 degrees C, benzene, an alkyl-subst. or halogenated monocyclic aromatic hydrocarbon or an inert polychlorinated aliphatic hydrocarbon of b.pt. 80-170 degrees C as solvent. The oxidation is pref. carried out at 90-120 degrees C for 5-20 mins. using an approximately equimolar amount of selenium dioxide. (I) are useful as intermediates for carontenoids. Thus, (I) can be reacted with beta-ionylidene-ethyl-triphenylphosphonium chloride under the conditions of the Wittig reaction to give corresponding acylols of retinal in almost quantitative yield; retinal itself is of economic, biological and pharmacological importance since its vitamin activity corresponds to that of vitamin A alcohol and it can readily be converted into beta-carotene. |
