A novel alkyl 4-methyl-3-formyl-penten-1-oate of the formula ##STR1## wherein R is alkyl of 1 to 5 carbon atoms and the dotted lines represent a double bond in the 3,4 or 4,5-position and their preparation and novel intermediates therefore and a novel process for the preparation of 4-methyl-3-formyl-pent-3-en-1-oic acid which is an intermediate for the preparation of compounds of the formula ##STR2## wherein R.sub.3 is selected from the group consisting of hydrogen and the residue of an alcohol R.sub.3 OH by the process of European Patent Application Ser. No. 0023849 published Feb. 11, 1981, which are used to prepare very active insecticidal esters.
一种新型的烷基4-甲基-3-酰基-
戊烯-1-酸酯,其
化学式为##STR1## 其中R是1至5个碳原子的烷基,虚线表示3,4或4,5位置的双键。该化合物的制备方法、新型中间体以及制备4-甲基-3-酰基-戊-3-烯-1-酸的新型方法,该方法是一种中间体,用于制备化合物##STR2## 其中R.sub.3选自氢和醇R.sub.3 OH残基的群体,该方法由欧洲专利申请编号0023849公开于1981年2月11日,用于制备非常活性的杀虫酯。