Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
  • C07C67/333—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton
  • C07C67/343—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/10—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with ester groups or with a carbon-halogen bond
  • C07C67/11—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with ester groups or with a carbon-halogen bond being mineral ester groups

Definitions

• the present invention relates to a novel process for preparing succinic esters substituted with unsaturated hydrocarbon groups in particular alkylidene groups. These compounds are convertible into alkyl substituted succinic esters that are used as electron donor compounds in the preparation of Ziegler-Natta heterogeneous catalysts for the polymerization of olefins.
• the transformation of alkylidene substituted succinates into alkyl substituted succinates is normally a clean reaction with an almost quantitative yield. Therefore, in order to industrially produce alkyl substituted succinates industrially exploitable, it is necessary to have an economically advantageous process for the production of alkylidene substituted succinic esters.
• Chem. Soc. (1949), 71, 3618-21 describes the preparation of several types of monoalkylidene substituted succinic esters carrying out the Stobbe reaction using potassium tert-butoxide as a base and tert-butanol as a solvent.
• the starting diethyl succinate was used in excess with respect to both the starting ketone (25%) and the base, which in turn was in excess (about 10%) with respect to the ketone.
• the highest yields were obtained using acetone as a ketone and were 92% with respect to the ketone, but much lower with respect to the succinate (76%).
• the base is preferably selected among alkoxides of formula R 5 OMe where R 5 is a C1-C15 hydrocarbon group and Me has the meaning given above. Particularly preferred among them are the alkoxides in which R 5 is a C1-C5 alkyl group and Me is Na or K. Especially preferred compounds are potassium tert-butoxide, sodium tert-butoxide, potassium ethoxide, sodium ethoxide. As a preferred aspect, such preferred alkoxides are used in combination with the aprotic solvents specified above. In particular the combination of the preferred alkoxides with the aprotic solvents like DMF or toluene is especially preferred.
• the above process is very suitable for obtaining the alkylidene substituted succinates in very high yields.
• the applicant found that by carrying out the process according to the above-mentioned conditions the work-up of the final reaction mixtures is very simple. In fact, in most of the cases the work-up comprises only a dilution of the reaction mixture with water and an extraction of the desired products with an appropriate organic solvent, which is then suitably removed.
• One class of preferred starting compounds among those of formula (I) is that in which R 1 is hydrogen and R is selected from C4-C20 hydrocarbon groups, preferably from those not having unsaturation on the carbon atom linked to the carbonyl of formula (I).
• the product of step (a) has at least one of the carboxylic groups not esterified.
• an esterification step must be carried out which is the step (b) of the process of the invention.
• the esterification step can be carried out according to any of the many methods known in the art.
• esters includes for example the esterification of a carboxylic acid through the reaction with an alcohol catalyzed by an acid or a base.
• the preferred method for carrying out the esterification according to the present invention is the reaction of the product of step (a) (the emiester) with a compound of formula R 6 X where X is halogen and R 6 is C1-C20 hydrocarbon group.
• X is selected from Br, Cl and I and R 6 is a primary C1-C8 alkyl group.
• R6 groups are methyl, ethyl, propyl, n-butyl and iso-butyl.
• ethyl bromide is especially preferred.
• This method has the advantage that the alkylidene substituted product of step (a) can directly be reacted with the compound of formula R 6 X without being first subjected to a preliminary work-up thereby saving time and increasing the yields.
• the temperature for carrying out step (b) is not critical. It generally ranges from about -30 to 150°C, more typically from -10 to 110°C. The skilled in the art can easily select, within these ranges, the optimum temperature by taking into account parameters like the boiling temperature of the reaction medium, that of the starting compounds and the like.
• the alkylidene-substituted succinates can be converted into alkyl substituted succinic esters that are used as electron donor compounds in the preparation of Ziegler-Natta heterogeneous catalysts for the polymerization of olefins. Such a conversion may be suitably obtained via the catalytic hydrogenation. Also this reaction is very known in the art. A review of this kind of reaction can for example be found in Comprehensive Organic Transformation: a guide to functional group preparation by R. C. Larock published by VCH Publishers. Among the various kinds of catalysts that can be used for carrying out this reaction, particularly preferred are the palladium or platinum deposited on carbon (Pd/C or Pt/C).
• the Pd/C containing 5% of Pd is particularly preferred.
• the Ni Raney catalyst is particularly preferred.
• the temperature at which this reaction is carried out may range from 0 to 150°C, more typically from 40 to 120°C.
• the hydrogen pressure is generally higher than the atmospheric pressure and preferably higher than 15 bar. The skilled in the art can easily select, within these ranges, the optimum temperature by taking into account parameters like the boiling temperature of the reaction medium, that of the starting compounds and the like.
• the reaction times for either of the above step cannot be foreseen. As a general indication the reaction time for these step may be from about 1 min to about 10 hours. More conveniently however, the reaction time is comprised from about 10 min to about 5 hours.
• the skilled in the art can control the state of the reaction by following the techniques known in the art and decide when and to stop it. As explained above this process is very attractive from an industrial standpoint because it allows to obtain the desired product in very good yields and with a minimal work-up.
• the process of the present invention is also very versatile. Depending on the compound (TT) that is used as starting material and on the conditions used, it allows the preparation of alkylidene monosubstituted esters, dialkylidene disubstituted succinic esters or monoalkylidene disubstituted succinic esters.
• alkylidene substituted succinic esters obtainable with the process of the invention are those of formula (TTT) below:
• R, R 1 , R 3 , R 4 and R 6 have the same meanings as above.
• One subclass of compounds of formula (TTT) obtainable with the process of the invention are those in which both R 3 and R 4 are hydrogen.
• specific preferred compounds obtainable are diethyl sec-butylidenesuccinate, diethyl cyclopropylidenesuccinate diethyl cyclohexylidenesuccinate, diethyl benzylidenesuccinate, diethyl cyclohexylmethylidenesuccinate, diethyl isobutylidenesuccinate, diethyl isopropylidenesuccinate, diethyl isopentylidenesuccinate and the corresponding products esterified with different alkoxy moieties.
• step (a) of the present invention is carried out choosing compounds of formula (TT) in which both R 3 and R 4 are hydrogen.
• the compound of formula (1) will be suitably selected on the basis of the type of alkylidene group to be introduced.
• R and R 1 groups are such as they form compounds of formula (I) chosen among acetone, cyclohexanone, cyclopentanone, cyclohexylmethyl aldehyde.
• ketones methyl ethyl ketone, methyl n-propyl ketone, cyclobutyl methyl ketone, 3-buten-l-yl methyl ketone, acetylcyclopropane, diethylketone, methoxyacetone, iso-propyl methyl ketone, 2-hexanone, 4-methyl-2-pentanone, methyl sec-butyl ketone, methyl tert-butyl ketone, ethyl propyl ketone, ethyl isopropyl ketone, iso-amyl methyl ketone, 4-methyl cyclohexanone, 2- methylcyclohexanone, 3-methylcyclohexanone, 2,2-dimethyl-3-pentanone, 2-heptanone 3- heptanone, di-n-propyl ketone, , dicyclopropyl ketone, di-iso-propyl
• Another subclass of compounds of formula (TTT) obtainable with the process of the invention are the di or trisubstituted succinic esters.
• the process of the invention can give dialkylidene disubstituted succinic esters and monoalkylidene di or trisubstituted succinic esters.
• Dialkylidene disubstituted succinic esters can for example be prepared by using a monoalkylidene substituted succinic ester as the starting compound of formula (TT).
• the starting succinic ester is a compound of formula (TT) in which n is 1 and both R 3 and R 4 are hydrogen.
• Particularly preferred are diethyl succinate and diisobutyl succinate.
• Especially preferred compounds are potassium tert-butoxide, sodium tert-butoxide, potassium ethoxide, sodium ethoxide.
• the base is preferably used in a substantially equimolar effective amount with respect to the alkylidene substituted compound.
• effective amount we mean that the amount of the base introduced should be equimolar to the alkylidene substituted compound once the corresponding molar amounts of other possible compounds reacting with the base have been subtracted.
• such preferred alkoxides are preferably used in combination with the aprotic liquid compounds used as reaction medium.
• the reaction medium which is preferably the same in all the steps (a), (b), (a2) and (b2), is selected from DMF or toluene. It is particularly interesting to note that all the above steps can be carried out in sequence without the need of any intermediate separation step. Also in this case the work- up of the reaction mixture is very simple. Dilution with water and extraction with organic solvents are the basic step for the work-up. Among the many organic solvents usable in the work-up, methyl tert-butyl ether, toluene, hexane and heptane are the most preferred.
• Example 8 The same procedure described in Example 8 has been repeated using different ketones or aldehydes as starting materials. The obtained results are reported in the table below. The yield is calculated after distillation of the products.

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• 2002
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