| 摘要 |
Compounds of the formula I <IMAGE> (I) wherein X is chlorine or fluorine, are suitable for producing 2,2-dimethyl-3-(2'-chloro-3',3',3'-trifluoroprop-1'-en-1'-yl)- and 2,2-dimethyl-3-(2',3'-dichloro-3',3'-difluoroprop-1'-en-1'-yl)-cyclopr opanecarboxylic acids and insecticidally effective esters thereof (pyrethroids). The cyclobutanones (I) can be produced by the addition reaction of 2,4,4,5-tetrachloro-5,5-difluoro- or 2,4,4-trichloro-5,5,5-trifluoropentane-1-carboxylic acid chloride with isobutylene, and rearrangement of the resulting 2-chloro-2-(2',2',3'-trichloro-3',3'-difluoropropyl)- or 2-chloro-2-(2',2'-dichloro-3',3',3'-trifluoropropyl)-3,3-dimethylcyclo butan-1-one in the presence of catalysts.
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