| 摘要 |
A novel process for the preparation of 2-(2',2',2'-trihalogeno-ethyl)-4-halogenocyclobutan-l-ones of the formula in which one of the radicals R1 and R2 is methyl and the other is hydrogen or methyl, or R1 and R2 together are an alkylene group having 2 to 4 carbon atoms, and X and Y are each chlorine or bromine, but if X is bromine Y must always be bromine, is disclosed. The process comprises reacting a 2,4,4,4-tetrahalogeno-butyric acid chloride in the presence of an organic base with an ethylene compound which is disubstituted in 1-position by the radicals R1 and R2, as defined above, to form a 2-(2',2',2'-trihalogenoethyl)-2-halogenocyclobutan-1-one and then rearranging the latter,in the presence of a catalyst, into a 2-(2',2',2'-trihalogenoethyl)-4-halogenocyclobutann-1-one of formula I. The 2-(2',2',-2'-trihalogenoethyl)-4-halogenocyclo-butan-1-ones of formula 1 are valuable intermediates for the preparation of 2-(2',2'-dihalogenovinyl)-cyclopropanecarboxylic acid and its insecticidally active esters. The 2-(2',2',2'-trihalogenoethyl)-4-halogenocyclobutan-1-ones of the above formula and the intermediates used for their preparation are novel compounds. |
