Preparation of ketones from 1,2-epoxides

Methyl ethyl ketone is produced in quantitative yields by isomerizing 1,2-butylene oxide or isomeric mixtures of n-butylene oxides in the presence of a tertiary butyl alcohol solution of dicobalt octacarbonyl.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the preparation of ketones by the catalytic 
isomerization or molecular rearrangement of epoxides. This invention 
particularly relates to the isomerization of 1,2-epoxides in alcohol 
solutions of dicobalt octacarbonyls. 
2. Description of the Prior Art 
As a general rule, the predominant isomerization product of 1,2-epoxides 
using soluble Lewis acids or heterogeneous catalysts is the corresponding 
aldehyde. By contrast, the predominant isomerization product of internal 
epoxides under similar isomerization conditions is the corresponding 
ketone. 
Although 1,2-epoxide isomerization generally favors molecular rearrangement 
of oxygen towards the alpha carbon atom of the epoxide, ketones have been 
prepared by the isomerization of 1,2-epoxides in the presence of alkanol 
solutions of dinuclear carbonyls. Eisenmann, J. L., J. Org. Chem., 27, 
2706 (1962) and U.S. Pat. No. 3,151,167. According to the '167 patent, 
suitable alkanols for this reaction are primary and secondary, mono- and 
dihydroxy lower alkanes, especially methanol, isopropanol and primary and 
secondary butanol. Methanol was particularly preferred. Suitable dinuclear 
carbonyls (disclosed in the '167 patent) are dicobalt octacarbonyl, 
dirhodium octacarbonyl and diiridium octacarbonyl. The latter 
compounds--dirhodium and diiridium octacarbonyls--have subsequently been 
shown to be nonexistent. Bor and Noack, J. Organometal Chem., 64, 
367(1974). 
SUMMARY OF THE INVENTION 
It has now been found that nearly guantitative yields of methyl ethyl 
ketone are obtained when 1,2-butylene oxide or isomeric mixtures of 
n-butylene oxides are isomerized with a tertiary butyl alcohol solution of 
dicobalt octacarbonyl ([Co(CO).sub.4 ].sub.2). 
DETAILED DESCRIPTION OF THE INVENTION 
As used herein, the term "isomeric mixture of n-butylene oxide" is intended 
to include mixtures of 1,2-butylene oxide with 2,3-butylene oxide (in 
either or both of its isomeric forms). 
According to the method of this invention, dicobalt octacarbonyl is added 
to tertiary butyl alcohol and the mixture is stirred for a period of time 
to form a solution of the catalyst. Then 1,2-butylene oxide or an isomeric 
mixture of n-butylene oxide is added to the solution and nearly 
quantitative yields of methyl ethyl ketone are obtained. The ketone may be 
separated from the reaction mixture by conventional distillation and 
filtration procedures. 
Preferably, the temperature of the reaction mixture is maintained near 
ambient temperatures, although temperatures within the range of about 
0.degree. to 100.degree. C. may be employed. The proportions of the 
reactants do not appear to be critical and may vary over a wide range. 
Preferably, the reaction is carried out in an inert atmosphere such as 
nitrogen, argon, helium, etc.

The following examples demonstrate the process of this invention and the 
unexpected results obtained thereby. 
EXAMPLE I 
In a 50 ml. three-necked flask equipped with thermometer, reflux condenser, 
addition funnel, and magnetic stirrer, 600 mg. of dicobalt octacarbonyl 
was added to 6 ml. of tertiary butyl alcohol under an argon atmosphere and 
stirred for 1 hour. No gas evolution was observed. Then, 6 ml. of 
1,2-butylene oxide was added via the addition funnel over a 10 minute 
period. No exotherm or color change was observed. Stirring continued at 
25.degree.-30.degree. C. for 6 hours, at which time the mixture was heated 
to 50.degree. C. and maintained at that temperature for 1/2 hour. The 
reaction mixture was analyzed by gas chromatography and the product was 
found to contain essentially only methyl ethyl ketone (98 wt. %+). A small 
amount of hydroxy ethers (less than 1%) was also present. 
EXAMPLE II 
Using the same apparatus described in Example 1, 600 mg. of dicobalt 
octacarbonyl was added to 6 ml. of tertiary butyl alcohol under an argon 
atmosphere and stirred for 1 hour at 30.degree. C. No exotherm or gas 
evolution was observed. Then 6 ml of 1,2-butylene oxide; cis-2,3-butylene 
oxide; and trans-2,3-butylene oxide was added via the addition funnel over 
a 2 minute period. The weight ratio of the butylene oxide feed components 
was 81 1,2-butylene oxide:4.5 cis-2,3-butylene oxide:14.5 
trans-2,3-butylene oxide. 
Samples of the reaction mixture were taken at the time intervals indicated 
below. Results obtained by gas chromatography are also shown. Throughout 
the reaction time shown, temperature was maintained at about 25.degree. C. 
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Time Analysis 
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11/2 hours 8% conversion of butylene oxides 
3 hours 78% conversion of butylene oxides 
(only 1,2-butylene oxide has 
reacted) 
5 hours 82% conversion of butylene oxides 
(all 1,2-butylene oxide has 
reacted and cis-2,3-butylene oxide 
has begun to disappear 
6 hours 90% conversion of butylene oxides 
20 hours 92% conversion of butylene oxides 
(unreacted butylene oxides consist 
essentially of trans-2,3-butylene 
oxide). 
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The reaction mixture remaining at the end of 20 hours was then heated to 
about 50.degree. C. and maintained at that temperature for 8 hours. The 
reaction mixture was analyzed by gas chromatography and the product was 
found to contain 98 wt. %+ methyl ethyl ketone. The analysis shows only 
0.6 wt. % of trans-2,3-butylene oxide remaining. 
The foregoing demonstrates that 1,2-butylene oxide is isomerized much 
faster than cis-2,3-butylene oxide, which, in turn, is isomerized much 
faster than trans-2,3-butylene oxide. 
The foregoing further demonstrates that an isomeric mixture of butylene 
oxides can be substantially completely isomerized according to the method 
of this invention to yield methyl ethyl ketone. 
COMATIVE EXAMPLE 
Using the same apparatus described in Example 1 600 mg. of dicobalt 
octacarbonyl was added to 6 ml. of isopropanol under an argon atmosphere 
and stirred for 1 hour. No gas evolution was observed. Then, 6 ml. of 
1,2-butylene oxide was added via the addition funnel over a 15 minute 
period. Samples of the reaction mixture were collected at reaction times 
of 2 hours and 16 hours while maintaining reaction temperature at about 
25.degree. C. Results obtained by gas chromatography are shown below. 
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Reaction Time Analysis 
______________________________________ 
2 hours 17% conversion of 1,2-butylene 
oxide to methyl ethyl ketone 
16 hours 89% conversion of 1,2-butylene 
oxide to a product consisting of 
3 wt. % butane, 90 wt. % methyl 
ethyl ketone and 7 wt. % hydroxy 
ethers. 
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After stirring the reaction mixture at about 25.degree. C. for 20 hours, 
the mixture was heated to 50.degree. C. and maintained at that temperature 
for 1/2 hour. The reaction mixture was then analyzed by gas chromatography 
and the product was found to contain 2 wt. % butane, 94 wt. % methyl ethyl 
ketone, and 4 wt. % hydroxy ethers. A small amount of butyraldehyde (less 
than 0.3 wt. %) was also present. 
Comparison of this Example with Example 1, supra, demonstrates the improved 
reaction rate and selectivities obtained when tertiary butyl alcohol 
solution of dicobalt octacarbonyl is employed as the isomerization media. 
It is significant that a change in the color of the reaction mixture (from 
brown to purple-red) of this Comparative Example was observed after 2 
hours reaction time. The color change was accompanied by a loss of methyl 
ethyl ketone selectivity for the system (see analytical results observed 
at 16 hours reaction time). 
By contrast, no color change was observed over the reaction times of either 
Example 1 or Example 2.