CA1218074A - Lactones - Google Patents

Abstract

ABSTRACT
"Lactones"
Esters of 3-.beta.,.beta.-dihalovinyl-2,2-dimethylcyclopropane-1-carboxylic acids are prepared from 4-.beta.,.beta.-dihalovinyl-3, 3-dimethyl butyrolactone by reaction with an inorganic acid halide to open the lactone ring with formation of the corresponding 4-haloacid halide, which with alcohols affords the corresponding 4-haloacid ester which is cyclised by bases to give the above product. The products are intermediate for insecticidal esters and the process offers fewer stages and higher yields than the processes hitherto described or used.

Description

~ ~ Dx', 28041/A

This invention relates to a process for the preparation of cyclopropane carboxylic acid esters, According to the present invention there is provided a process by which esters of the formula:

~ = CH Cl3 y/ \CEI--cl ~ CH3 ~ R
CO2Rl wherein R1 is a lower alkyl group, R is a hydrogen atom or a cyano,carboxy, methyl, ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, carboxymethyl or cyanoms~hyl group and each Y is a chlorine or bromine atom, are prepared by treating a lactone o~ formula ~H3 \ C=CH - CH- ~ - -CH3 ~ o/IR

wherein R and Y have the previously de~ined meanings, with an acid chloride or bromide and treating the product with an alcohol of the formula RlOH and a base.

This process proceeds in three stages which may be carried out. if desired, especially in respect o-E the first and second stages, withou~ isolation of the inter-mediate products, Each .individual stage, and the two combinations of successive stages, are also features of the inven-tion, In the first stage of the process the lactone ring is opened and the appropriate 3,3-dimethyl-4-chloro (or bromo)- 6,$-dichloro (or dibromo) hex-5-enoyl chloride (or bromide) is obtained, In this stage it is preferred that R be a hydrogen atom or a methyl, ethyl, isopropyl, n-propyl, tert-butyl, n-bu-tyl, carboxymethyl or cyano-methyl group~
The first stage of the process is conveniently carried out using at least a molar amount, and preferably not more than 1,5 molar amounts, of acid chloride or bromide at a temperature between ambient and the boiling point of the reaction mixture, As acid chloridesor bromides there may be mentioned especially inorganic acid chlorides such as thionyl chloride, phosphorous pentachloride and phosphorus oxychloride, which provide hexenjoyl` chloride having a 4-chloro substituent, and inorganic acid bromides such as thionyl bromide and phosphorus pentabromide, which provide acid bromides having a 4~bromo substituent, The second stage of the process, treatment with the alcohol of the formula RlOH, is preferably carried out without isolation of the product of the first stage.
The alcohol is preferably used in excess, for example 1,5 molar proportions, and a reaction temperature from ambient to the boiling point of the reaction mixture may conveniently be used. The alcohol RlOH is preferably methanol or ethanol.
The product of the second stage, the ester of the acid of which the acid chlo.ride resulted from the first stage, may if desired be isolated by conventional means, for example removal of excess alcohol, RlOH, and distilla-tion under reduced pressure, but it is not usually necessary to carry out such isolation before carrying out the third stage, The third stage, treatment with the base, may be carried out at a temperature between ambient and the boiling point of the reaction mixture using a solvent conveniently the alcohol, RlOH, The base is preferably an alkali metal alkoxide, for example NaORl, but may be another alkoxida or sodium hydroxide in ethanol, ~ he amount of base is preferably from 2.0 to 3,0 molar equivalents, The cyclopropanecarboxylic ester may be isolated by conventional means, for example neutralisation by the addition of e.g, dilute sulphuric acid, separation from the residue of any salt, removal of excess alcohol by distillation, addition to water and extraction with a water-immiscible so].vent, After removal of the solvent the product may be purified by distillation under reduced pressure.
The cyclopropanecarboxylic ester may be converted into an insecticidal ester by known means, for example an ester .interchange reaction with e,g, m-phenoxybenzyl alcohol using a catalyst uuch as potassium tert,-butoxide or may be converted into for example the corres-ponding acid or acid chloride which may then be esterifiedwith e,g, m-phenoxybenzyl alcohol, The process of the inventiOn affords a route to insecticidal esters of 3~ dichloro~or dibromo) vinyl-2,2-dimethylcycloproparle-~-~arboxylic acids which has fewer stages and gives higher yields than the routes hitherto described or used.
The invention is illustxated but not limited by the following examples in which all parts and percentages are by weight unless stated otherwise.

ExamPle ,1 29.08 Parts of thionyl chloride were added dropwise with stirring at room temparature to 20.8 parts of 2~ dichlorovinyl)-3,3-dimethyl~5-oxotetrahydrofuran, The mixture was boiled or 1 hour after which the unreacted thionyl chloride was distilled o~f to give crude 3,3-dimethyl-4,6,6-trichlorohex 5-enoyl chloride 20 Parts of ethanol were then added dropwise, the temperature being maintained at below 30C and the mixture was then refluxed for 1 hour. The product was dis-tilled under reduced pressure giving 15.28 parts of ethyl 4,6,6 trichloro-3,3-dimethylhex-5-enoate, which contained a minor amount of unchanged lactone Example 2 A slurry of 11.2 parts of potassium t-butoxide in 200 parts of toluene wa~ added 510wly to 13.7 parts of ethyl 4,6,6 trichloro-3,3-dimethyl-hex-5-enoate stirred at below 0C and stirred at below 0C for a further 1 hour.
The mixture was neutralised to pH 6 with concentxated hydrochloric acid Water was added to dissolve the precipitated salt and the toluene layer separated. The water layer was extracted again with toluene and the toluene then removed from the combined extracts giving in nearly theoretical yield the mixed cis and trans forms of ethyl 3~ dichlorovinyl-2,2-dimethylcyclopropanecarboxylate.
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Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the preparation of cyclopropane carboxylic acid esters of the formula:

wherein R1 is a lower alkyl group, R is a hydrogen atom or a cyano, carboxy, methyl, ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, carboxymethyl or cyanomethyl group and each Y is a chlorine or bromine atom, which comprises treating a lactone of the formula:

wherein R and Y have the previously defined meanings, with an inorganic acid chloride or bromide and treating the product with an alcohol of the formula R1OH and a base.

2. A process for the preparation of a 4-haloacid halide of the formula:

Y2C=CH.CH Hal.C(CH3)2CHR.COHal wherein R and Y have the meanings stated in Claim 1 and Hal represents a chlorine or bromine atom, which comprises treating a lactone of the formula:

with an inorganic acid chloride or bromide.

3. A process as claimed in Claim 2 wherein R is a hydrogen atom or a methyl, ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, carboxymethyl or cyanomethyl group.

4. A process for the preparation of a haloacid ester having the formula:
Y2C = CH.CH Hal.C(CH3)2.CHR.CO2R1 wherein R1, R and Y have the meanings stated in Claim 1 and Hal represents a chlorine or bromine atom which comprises carrying out in succession the process of Claim 2 and treating the 4-haloacid halide having the formula defined in Claim 2 with an alcohol of the formula R1OH.

5. The process of reacting V
with R'OH, to produce the compound II of formula:

wherein Hal is chlorine or bromine R1 is loweralkyl.

6. The process of reacting VI

with C2H5OH to produce the compound IV of formula: