Process for the preparation of cyclopropane derivatives, intermediates in the synthesis of pyrethroid insecticides

A process for the preparation of a compound of formula:

• ##STR18## wherein both groups X are chlorine, bromine or trifluoromethyl, or one X is chlorine or bromine and the other is trifluoromethyl, and Y is --CN or --COOR in which R is an alkyl group of 1 to 4 carbon atoms, in which a compound of the formula:
• ##STR19## wherein X.sup.1 is chlorine or bromine and Y has the meaning defined above, is reacted with a diene of the formula:
• ##STR20## wherein X has the meaning defined above, the reaction taking place at a temperature of from 0.degree. to 140.degree. C. for a time of 30 minutes to 30 hours, in the presence of from 0.01 to 0.1 mol per mol of the diene of a catalyst selected from the group consisting of metallic copper, cupric acetate, cupric chloride, copper stearate, cupric oxide, cuprous cyanide, cuprous chloride, copper acetylacetonate, di-.mu.-methoxobis(pentane-2,4-dionato)dicopper and di-.mu.-methoxobis(salicylaldehydato)dicopper, from 0.5 to 2.0 mols per mol of the diene of a base selected from the group consisting of an alkali or alkaline earth metal carbonate or borate, an alkali metal (1-4C) alkoxide and an alkaline earth metal oxide, and in a solvent selected from the group consisting of water together with a phase transfer catalyst, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, tert.butanol, n-pentanol, isopentanol, n-hexanol, cyclohexanol, 2-methoxyethanol, 2-ethoxyethanol, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, secondary butyl acetate, tert.butyl acetate, n-pentyl acetate, isopentyl acetate, n-hexyl acetate, cyclohexyl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, acetonitrile, dimethylformamide, dimethylsulphoxide and N,N-dimethylacetamide.

A process for the preparation of a compound of formula:

• ##STR21## wherein both groups X are chlorine, bromine or trifluoromethyl, or one X is chlorine or bromine and the other is trifluoromethyl, and Y is --CN or --COOR in which R is an alkyl group of 1 to 4 carbon atoms, in which a compound of formula:
• ##STR22## wherein Y has the meaning defined above, is reacted with a compound of the formula:
• ##STR23## wherein X has the meaning defined above and X.sup.1 is chlorine or bromine, the reaction taking place at a temperature from 0.degree. to 140.degree. C. for a time of from 30 minutes to 30 hours, in the presence of from 0.01 to 0.1 mol per mol of the compound of formula (V) of a catalyst selected from the group consisting of cupric chloride, cupric acetate, cuprous chloride, cuprous cyanide and basic cupric carbonate, and in a solvent selected from the group consisting of water together with a phase transfer catalyst, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, tert.butanol, n-pentanol, isopentanol, n-hexanol, cyclohexanol, 2-methoxyethanol, 2-ethoxyethanol, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, secondary butyl acetate, tert.butyl acetate, n-pentyl acetate, isopentyl acetate, n-hexyl acetate, cyclohexyl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, acetonitrile, acetic acid, dimethylformamide, dimethylsulphoxide and N,N-dimethylacetamide.