US3515761A

US3515761A - Method of producing cyclopropanes

Info

Publication number: US3515761A
Application number: US738124A
Authority: US
Inventors: William D Hoffman; Jin Sun Yoo
Original assignee: Sinclair Research Inc
Current assignee: Sinclair Research Inc
Priority date: 1968-06-19
Filing date: 1968-06-19
Publication date: 1970-06-02
Anticipated expiration: 1987-06-02

Description

United States Patent Ofice 3,515,761 Patented June 2, 1970 U.S. Cl. 260-666 15 Claims ABSTRACT OF THE DISCLOSURE A method of using a pentacyanocobaltate complex to catalyze the formation of cyclopropanes in an aqueous medium is disclosed. 1,3-dihalogenated alkyl hydrocarbons are reacted in an inert atmosphere at about to 110 C. with the cyanocobaltate and in the presence of an optional stabilizer such as an alkali metal halide or hydroxide.

This invention is directed to the production of cycopropanes. More specifically, the invention relates to a novel method of preparingcyclopropanes from 1,3-d ihalogenated alkyl hydrocarbons in contact with an aqueous solution of a pentacyanocobaltate.

The prior art shows various means of preparing cyclopropanes, but such methods are normally expensive, and do not give high yields. Included in these methods is the use of zinc in various forms in the reaction. Generally the zinc is employed in an alcohol solution with some form of a halide also present (e.g. atomic iodine, a salt, etc.). The hydrocarbon cyclized is a 1,3-dihalogenated compound, which in the presence of zinc is reduced thus forming a cyclopropane and the corresponding zinc halide. This method has the disadvantage of consuming the zinc and thus increasing the expense of the reaction. The use of Werner complexes is also known in the art, but yields in the known methods range only to about 80% of theoretical, while the present invention has given yields as high as about 90 to 95%.

The method of the present invention involves the reaction in an inert atmosphere of an aqueous cyanocobaltate complex with a 1,3-dihalogentated alkyl hydrocarbon thereby causing the cyclopropane to form. The reaction is preferably conducted while in contact with a stabilizer for the complex ion. In a specific embodiment, the method comprises preparing an aqueous solution by the addition of a water-soluble cobalt salt, e.g. chloride, bromide, or nitrate, and an alkali metal cyanide to water in an inert atmosphere and with an excess of cyanide to cobalt, such as a mole ratio of cyanide to cobalt of about 5.1 to 7.521, preferably about 5.1 to 73:1, and at a concentration of [Co(CN) ions of about 0.5 to 1.5 molar, preferably 0.1 to 1 molar. The solution can be stabilized by the addition of a minor amount, say about 0.5 to 5 weight percent, preferably about 1 to 3 weight percent,

based on the total water content, of an hydroxide of halide metal having an atomic number from 11 to 55. For example the heavier alkali metal halide can be a chloride or bromide of for instance cesium or rubidium, or the alkali metal hydroxides of sodium, potassium, cesium or rubidium. The stabilizer is not required, but enhances the life of the complex ion, and thus is a preferred component. While the above solution is being stirred, in the inert atmosphere and at a temperature of from about 5 to 110 C., preferably about 20 to 80 C., the 1,3-dihalogenated alkyl hydrocarbon can be added. As the reaction proceeds the product cyclopropane can be collected as a gas or liquid, depending on its boiling point.

The 1,3-dihalogenated alkyl hydrocarbon employed in this invention is of the general structure:

wherein X is a halogen having an atomic number of from 17 to 53, and R is hydrogen or an alkyl radical of from 1 to 3 carbon atoms, the total number of carbon atoms in the molecule being up to about 10, preferably up to about 8.

The present invention will be better illustrated by the following examples.

EXAMPLE I An aqueous solution of 0.15 molar potassium pentacyanocobalt was prepared using 5 gm. cobalt chloride hexahydrate and 7 gm. potassium cyanide in 140 ml. water and under a nitrogen atmosphere. The solution was stabilized by adding 2 gm. of potassium hydroxide, and Was prepared in a 1000 ml. three-neck flask using a 100 ml. addition funnel, a 250 ml. gas buret with leveling bulb and a serum cap for the injection of the substrate. About 1.0 ml. of 1,3-dibromopropane was injected through the serum cap and the immiscible system stirred until about 250 ml. of gas were generated. The system was maintained at room temperature during the reaction. The product gas was analyzed and found to contain:

Percent cyclopropane Propene 19 Propyne Trace Hydrogen Trace l-bromopropane Trace EXAMPLE II The procedure of Example I was repeated using a hydrogen atmosphere and employing 7.1 gm. of potassium cyanide and a 0.15 in. potassium pentacyanocobaltate solution, with the following products being obtained.

Percent Cyclopropane 74 Propene 15 Propane 10 EXAMPLE III The procedure of Example I was followed, but 7.1 gm. of potassium cyanide, 2 g. of 1,4-dibromobutane, and a reaction temperature of 80 C. were used. The following are the results of the product gas analysis:

EXAMPLE IV 1,3-diiodobutane was reacted in the manner described in Example III using 1.5 gm. of potassium hydroxide as the stabilizer with the following products being obtained:

Percent Methylcyclopropane 93 Butene 6 3 EXAMPLE V 1,5-diiodopentane was reacted in the manner described in Example III with the following products being ob tained:

Percent Cyclopentane Pentene-l 80 N-pentane 10 1,4-pentadiene 7 EXAMPLE VI 1,6-dibromohexane was reacted in the manner described in Example III with the following products being obtained:

- Percent Cyclohexane Hexenes 82 N-hexane 17 EXAMPLE VII 2,3-dibrmobutane was reacted in the manner described in Example I with the following products being obtained:

Z-butene:

Percent Trans 85 Cis 1.1

l-butene Trace It is claimed:

1. A method of producing cyclopropanes from 1,3- dihalogenated alkyl hydrocarbons of the general structure:

wherein X is a halogen having an atomic number of from 17 to 53 and R is selected from the group consisting of hydrogen and alkyl hydrocarbons of from 1 to 3 carbon atoms, the total number of carbon atoms being up to about 10, comprising reacting said dihalogenated alkyl hydrocarbon in an inert atmosphere and in contact with an aqueous solution of a pentacyanocobaltate complex containing an excess of cyanide ions, at a temperature of 2 from about 5 C. to 110 C.

2. The method of claim 1 wherein the cyanide to cobalt mole ratio is about 5.1 to 7.5: l.

3. The method of claim 2 wherein said pentacyanocobaltate complex concentration is from about 0.1 to 1 molar.

4. The method of claim 1 wherein there is included in the reaction mixture a minor amount of a stabilizer for the complex, said stabilizer being selected from the group consisting of alkali metal halides and alkali metal hydr'oxides, said alkali metal having an atomic numberv 8. The method of claim 7 wherein said temperature 1 is from about 20 to C.

9. The method of claim 8 wherein X is iodine 10. The method of claim 8 wherein X is bromine. 11. The method of claim 8 wherein said 1,3-dihalogenated alkyl hydrocarbon is 1,3-dibromopropane.

12. The method of claim 8 wherein said 1,3-dihalogenated alkyl hydrocarbon is 1,3-diiodobutane.-

13. The method of claim 8 wherein the stabilizer is.

potassium hydroxide.

14. The method of claim 11 wherein the stabilizer is.

potassium hydroxide.

15. The method of claim 12 wherein the stabilizer is potassium hydroxide.

References Cited UNITED STATES PATENTS 3,450,782 6/1969 Connor 260-666 3,074,984 1/1963 Simmons.

2,098,239 11/1937 Hass et al. 260-666 2,102,556 12/ 1937 Hass et a1. 260-666 DELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner