Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-01-26
2002-06-25
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S315000, C568S346000, C568S347000, C568S388000, C568S391000
Reexamination Certificate
active
06410795
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for the preparation of beta-diketones and, more particularly, to a process for the production of beta-diketones by means of a homogeneous or nearly homogeneous liquid reaction medium wherein a carboxylic acid ester is reacted with a ketone in the presence of a condensing agent that is a sterically hindered alkali metal alkoxide dissolved in an aromatic hydrocarbon.
2. Description of Related Art
Beta-diketones are highly valuable compounds having advantageous utility in a wide variety of applications. For example, U.S. Pat. No. 3,001,970 discloses the use of dibenzoylmethane to prevent the discoloration of vinylidene chloride. U.S. Pat. No. 3,493,536 discloses that diaroylmethane compounds provide stabilizing action against the sensitizing effect of bismuth or antimony compounds on chlorine containing materials. Aryl substituted beta-diketones are shown by U.S. Pat. No. 3,994,869 to be useful as accelerators for the photodegradation of polyolefins. U.S. Pat. No. 4,427,816 discloses beta-diketones in combination with hydrotalcites as stabilizer compositions for halogen containing polymers.
The preparation of beta-ketones is reported in Organic Reactions (Vol. 8, 1959), Chapter 3, (pages 59-195) entitled “The Acylation of Ketones to Form &bgr;-Diketones or &bgr;-Keto Aldehydes.” The article states in its introduction at page 61, “Under certain conditions, a ketone having an &agr;-hydrogen atom may be acylated with an ester, an acid anhydride, or an acid chloride to form a &bgr;-diketone or, when the acylating agent is a formic ester, &bgr;-keto aldehyde. The process consists in the replacement of an &agr;-hydrogen atom of the ketone by an acyl group; . . .”
Unfortunately, the acylation of ketones, as achieved by using previously known procedures, is a reaction that does not readily proceed in an economical manner. On page 66 of this same text, for example, it is pointed out that the acylation of ketones with esters in the presence of a basic reagent may be accompanied by certain side reactions. Among the side reactions that may occur are self-condensation of the ketone, self-condensation of the ester, aldol reaction of the ester with the carbonyl group of the ketone, or a Michael condensation of the ketone. Also, the basic condensing agent may react with the carbonyl group of the ester.
The preparation on a laboratory scale of dibenzoyl methane by the reaction of acetophenone and ethyl benzoate in the presence of sodium ethoxide and the absence of solvent is reported by Magnani and McElvain in Organic Synthesis, Collective Volume 3, pp. 251-253. This reaction used 4 moles of ethyl benzoate and 0.5 mole of acetophenone. The reaction mixture was gelatinous after all of the ethoxide had been added and was too viscous to be stirred with a Hershberg stirrer. The yield of dibenzoyl methane recovered from the reaction mixture, as reported, was 62-71% based on the acetophenone.
In general, the reaction of the ester, the ketone, and the basic condensing agent in the presence of an inert solvent is known, as in the aforementioned Organic Reactions article at page 112. This article further states that the beta-diketone may be isolated by the usual technique of distillation or filtration, but often it is isolated as its copper derivative from which the beta-diketones need to be regenerated by further chemical reactions with concomitant yield losses, generation of waste products, and laborious recovery of copper.
The use of copper derivatives is an expensive and environmentally undesirable procedure. Furthermore, the occurrence of side reactions would prevent the commercial success of the process. Then, too, loss of solvent and the need to use fresh solvent for each reaction is commercially unattractive.
U.S. Pat. No. 3,994,869, mentioned above, discloses the preparation of aryl substituted beta-diketones by the reaction of acetophenone or a substituted acetophenone with an ester in the presence of a base, such as sodium methoxide, sodium ethoxide, and sodium hydride. The acetophenone may be represented by the structural formula:
wherein R is selected from the group consisting of hydrogen, halogen, C
1
to C
9
alkyl and C
1
to C
9
alkoxy. Representative esters identified as useful in this reaction are methyl stearate, ethyl benzoate, ethyl acetate, and ethyl laurate. This reaction, according to the patent, can be carried out in a suitable aprotic solvent, such as toluene or tetrahydrofuran. Recovery of the desired product is stated to be by methods that are now known in the art.
While it has been known that beta-diketones can be made by the reaction of acetophenone or a substituted acetophenone with an ester in the presence of base, this procedure has drawbacks which have limited its commercial acceptability. U.S. Pat. No. 4,482,745 discloses that handling large quantities of strong bases, such as sodium ethoxide makes their use undesirable and costly for large scale production. Yet, sodium alkoxides are preferred bases since only one mole is consumed, whereas two moles of metallic sodium, sodium amide, or sodium hydride would normally be required. Then, too, metallic sodium or sodium hydride are more hazardous than the alkoxides. Aromatic beta-diketones in high yields and purity can be readily made by this process. The method taught by this patent comprises reacting acetophenone with from 5 to 10 molar equivalents of methyl benzoate in the presence of from 1 to 2 molar equivalents of calcium oxide, in a temperature range of from 150° to 200° C. for from three to six hours under an inert nitrogen atmosphere while continuously removing the methyl alcohol which is formed during the reaction.
U.S. Pat. No. 5,015,777 and European Patent No. 0 507 013 B1 disclose a process for the preparation of aromatic beta-diketones by the reaction of an acetophenone and a molar excess of an alphatic ester or an ester of benzoic acid in the presence of sodium alkoxide condensation agent in an aromatic hydrocarbon solvent. Also disclosed is a method of recycling the solvent and excess ester reactant after separation of the aromatic beta-diketone product.
U.S. Pat. No. 5,344,992 and European Patent No. 0 454 624 B1 disclose a process for the preparation of 1,3-diketones of formula I
wherein R
1
and R
2
are each independently of the other C
1
-C
20
alkyl, phenyl or phenyl which is substituted by halogen, hydroxy, NO
2
, C
1
-C
4
alkyl and/or C
1
-C
4
alkoxy, C
7
-C
9
phenylalkyl or a radical of formula II
—A—X—R
4
(II)
wherein A is C
1
-C
12
alkylene, phenylene or phenylene which is substituted by halogen, hydroxy, NO
2
, C
1
-C
4
alkyl and/or C
1
-C
4
alkoxy, or is C
1
-C
12
alkylene which is substituted by hydroxy, halogen and/or alkoxy, X is oxygen or sulfur, and R
4
is hydrogen, C
1
-C
18
alkyl, phenyl or phenyl which is substituted by halogen, hydroxy, C
1
-C
4
alkyl, NO
2
and/or C
1
-C
4
alkoxy, or is C
7
-C
9
phenylalkyl, and R
3
is hydrogen, C
1
-C
20
alkyl, phenyl or phenyl which is substituted by halogen, hydroxy, C
1
-C
4
alkyl, NO
2
and/or C
1
-C
4
alkoxy, or is C
7
-C
9
phenylalkyl. The process comprises carrying out a Claisen condensation of a ketone of fornula III
and an ester of formula IV
or
wherein m is 2 to 10 and R
5
is C
1
-C
5
alkyl, phenyl or phenyl which is substituted by halogen, C
1
-C
4
alkyl or hydroxy, the reaction being carried out with the base used as catalyst, a hydride of an alkali metal or alkaline earth metal or an alcoholate of C
1
-C
5
alkali metal or C
1
-C
5
alkaline earth metal, in a mixture of dimethyl sulfoxide and at least one organic solvent which is inert under the reaction conditions. The use of dimethyl sulfoxide is a disadvantage owing to the difficulty of completely removing it from the product and of recovering it for reuse without significant losses.
U.S. Pat. No. 5,672,646 discloses a stabilizing composition for a chlorine-containing polymer (PVC), characterized in that it comprises the unpurified crude product resulting from
Bacaloglu Radu
Fisch Michael H.
Krainer Edward
Crompton Corporation
Grandinetti Paul
Padmanabhan Sreeni
Reitenbach Daniel
Witherspoon Sikarl A.
LandOfFree
Process for base-promoted condensation reactions and base... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for base-promoted condensation reactions and base..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for base-promoted condensation reactions and base... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2900306