Improved process for preparing cyclopropyl compounds from alkenes

Abstract

The invention relates to an improved process for preparing cyclopropyl compounds from alkenes through reaction of the alkene in the presence of bromochloromethane, elemental zinc, and elemental copper or copper compounds (cyclopropanation reaction).

Claims

1. A process for preparing cyclopropyl compounds that comprises the reaction of the corresponding alkene, which contains at least one carbon-carbon double bond, with bromochloromethane in the presence of (i) elemental zinc, (ii) catalytically active amounts of elemental copper and/or copper(I) compounds and/or copper(II) compounds, and (iii) at least one solvent, wherein the reaction of the alkene takes place without addition of organosilicon compounds, and that the elemental zinc has a lead content of not more than 0.005% by weight.

2. The process for preparing cyclopropyl compounds as claimed in claim 1, wherein the alkene is a compound of formula (I), ##STR00003## and the cyclopropyl compound obtained is a compound of formula (II), ##STR00004##

3. The process as claimed in claim 1, wherein the elemental zinc has a particle size distribution D90.sub.mass of not more than 0.5 mm.

4. The process as claimed in claim 1, wherein the elemental zinc has a total content of other metals of not more than 1% by weight.

5. The process as claimed in claim 1, wherein the elemental copper has a total content of other metals of not more than 1% by weight.

6. The process as claimed in claim 1, wherein the copper compounds are selected from copper(I) chloride, copper(II) chloride, copper(II) phosphate, copper(II) carbonate and mixtures thereof.

7. The process as claimed in claim 1, wherein the haloalkylsilane is a chlorotrialkylsilane.

8. The process as claimed in claim 1, wherein the chlorotrialkylsilane is selected from chlorotrimethylsilane, chlorotriethylsilane, chlorotributylsilane, chlorotriisobutylsilane, chlorotrihexylsilane, and mixtures thereof.

9. The process as claimed in claim 1, wherein the at least one solvent is an ether, selected from diethyl ether, 1,2-dimethoxyethane, methyl tert-butyl ether, tetrahydrofuran, cyclopentyl methyl ether, and mixtures thereof, and/or an aromatic hydrocarbon, toluene.

10. The process as claimed in claim 1, wherein the bromochloromethane has a purity of at least 98% by weight and/or a water content of less than 0.02% by weight.

11. The process as claimed in claim 1, wherein from 1.5 to 4 mol, of metallic zinc based on 1.0 mol of the alkene is used.

12. The process as claimed in claim 1, wherein the catalytically active amount of elemental copper and/or copper(I) compounds and/or copper(II) compounds is used in a total amount of from 0.001 to 0.1 mol, based on 1.0 mol of the alkene.

13. The process as claimed in claim 1, wherein from 1 to 3 mol of bromochloromethane based on 1.0 mol of the alkene is used.

14. The process as claimed in claim 1, wherein the reaction temperature is from 55 to 85° C., from 60 to 80° C.

15. The process as claimed in claim 1, wherein the alkene, compound of formula (I), bromochloromethane, elemental zinc, catalytically active amounts of elemental copper and/or copper(I) compounds and/or copper(II) compounds, and at least one solvent, are mixed together to prepare the cyclopropyl compound giving rise to a crude mixture, and the crude mixture is hydrolyzed at the end of the preparation.

16. The process as claimed in claim 1, wherein the preparation of the cyclopropyl compound takes place in the presence of 0.1% to 5% by weight, based on the total weight of the crude mixture, of a crude mixture from a previous preparation of the cyclopropyl compound, based on the amount of alkene used.

Description

EXAMPLES

[0036] Example 1 (According to the Invention) [1-(4-chlorophenyl)-2-cyclopropylpropan-1-ol; Compound of Formula (II)]

[0037] All steps in this reaction prior to hydrolysis of the reaction mixture were carried out under a nitrogen atmosphere. A reactor was initially charged with 79.4 g (0.85 mol) of dimethoxyethane, 152.0 g of 4-(4-chlorophenyl)-3-methylbut-1-en-4-ol [compound of formula (I)] (content 97.0% by weight, 0.75 mol), 193.3 g (2.07 mol) of toluene, 120 g of zinc powder (1.84 mol), and 0.188 g (1.9 mmol) of copper(I) chloride at ambient temperature and also 1-2 g of unhydrolyzed reaction mixture from a previous reaction. The mixture was heated to 85° C. while stirring. On reaching this temperature, 7.25 g of bromochloromethane was metered in over the course of 10 minutes. After 6 minutes, an exothermic reaction commenced and the reaction mixture warmed by 2° C. The reaction mixture was then adjusted to a temperature range of 67 to 73° C. by cooling. 179.1 g (1.38 mol) of bromochloromethane was then metered into the reaction mixture such that the temperature of the reaction mixture continued to remain within a range from 67 to 73° C. This was accompanied by an escape of gaseous methyl chloride from the reaction mixture, which was discharged from the reactor into a scrubber via a stream of nitrogen. At the end of the metered addition, the reaction mixture was mixed for 3 hours by stirring. The temperature of the reaction mixture was then lowered to 45° C. with stirring. To hydrolyze the reaction mixture, the reaction mixture thus cooled was added with stirring to a mixture of 110 g of hydrochloric acid (30% by weight) and 500 g of water such that the pH of the aqueous phase of the two-phase mixture was 6.5 to 7.5. After phase separation, the first upper organic phase was separated off. The first lower aqueous phase was mixed with 50 g of toluene, stirred, and left to stand to allow the phases to separate. The second upper organic phase was separated off and combined with the first upper organic phase. The solvent was removed from the combined organic phase by distillation at 90° C. and 20 hPa, affording the product (1-(4-chlorophenyl)-2-cyclopropylpropan-1-01) (168.4 g, content: 85.4% by weight) as the crude product in a yield of 91% of theory.

TABLE-US-00001 TABLE 1 The experiments according to examples 2 and 3 were carried out in analogous manner to the procedure for example 1, but with the parameters listed in the table. Methylene Molar component/ Yield Reaction equivalents Mol % of molar (% of Example temperature of zinc *.sup.) Catalyst catalyst *.sup.) equivalents *.sup.) theory) 1 67 to 2.45 CuCl 0.25 Bromochloro- 91 73° C. methane/1.91 2 85° C. 2.45 CuCl 0.25 Dibromo- 82 methane/1.91 3 85° C. 2.45 CuCl 0.25 Dichloro- 0 methane/1.91 *.sup.) based on alkene