A method of preparing certain dihalogen vinyl cyclopropane carboxylic acid esters of the formula ##STR1## wherein R is an alkyl moiety and X is chlorine or bromine by exposing a dihalogen vinyl dihydrofuran of the formula ##STR2## to light, e.g., ultraviolet light. Also disclosed is a method for preparing such 2,4,4-trimethyl-3-carbalkoxy-5-(.beta.,.beta.-dihalogenvinyl)-4,5-dihydrof urans by reaction of a .beta.-alkoxycrotonic acid ester or 3,3-bisalkoxybutyric acid ester with a 1,1,1-trihalogen-4-methyl-3- or -4-pentene-2-ol in the presence of an acid catalyst. Also disclosed is a method of converting such 2,4,4-trimethyl-3-carbalkoxy-5-(.beta.,.beta.-dihalogenvinyl)-4,5-dihydrof uran by thermal rearrangement into 2,5,5-trimethyl-3-carbalkoxy-4-(.beta.,.beta.-dihalogenvinyl)-4,5-dihydrof urans. Such 2,4,4- and 2,5,5-trimethyl-3-carbalkoxy-5-(.beta.,.beta.-dihalogenvinyl)-4,5-dihydrof urans are new.
一种制备某些二卤代
乙烯基环丙烷羧酸酯的方法,其
化学式为##STR1##其中R是烷基,X是
氯或
溴,方法是将二卤代
乙烯基二氢
呋喃的
化学式##STR2##暴露于光线下,例如紫外线。还公开了一种制备这种2,4,4-三甲基-3-羧基烷氧基-5-(β,β-二卤代
乙烯基)-4,5-二氢
呋喃的方法,该方法是在酸催化剂存在下,将β-烷氧基
巴豆酸酯或3,3-双烷氧基
丁酸酯与1,1,1-三卤代-4-甲基-3或
4-戊烯-2-醇反应。还公开了一种将这种2,4,4-三甲基-3-羧基烷氧基-5-(β,β-二卤代
乙烯基)-4,5-二氢
呋喃通过热重排反应转化为2,5,5-三甲基-3-羧基烷氧基-4-(β,β-二卤代
乙烯基)-4,5-二氢
呋喃的方法。这些2,4,4-和2,5,5-三甲基-3-羧基烷氧基-5-(β,β-二卤代
乙烯基)-4,5-二氢
呋喃是新的。