Process for the preparation of carbonyl compounds by...

Details Process for the preparation of carbonyl compounds by... Process for the preparation of carbonyl compounds by...

2001-10-12

2003-01-14

Wilson, James O. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S385000, C568S397000, C568S402000, C568S404000

Reexamination Certificate

active

06506942

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the preparation of carbonyl compounds by cleavage of hydroxycarboxylic acids in the presence of a Brönstedt base and a hydroxyl-free solvent.
2. Background Art
&bgr;-Hydroxycarboxylic esters, &bgr;-hydroxycarboxamides and &bgr;-hydroxyketones are usually cleaved thermally or under acid or base catalysis into the corresponding carbonyl compounds by retroaldolization (as, for example, in WO 9615142).
For example, the cleavage of di-, tri- and tetrasubstituted &bgr;-hydroxypropionic acids in water in the presence of the bases potassium hydroxide or potassium carbonate, in aqueous alcoholic solution in the presence of the base sodium hydroxide, and in 1-propanol in the presence of the base sodium 1-propanolate, is known from D. Ivanoff, BULL. SOC. CHIM. France 36, 321 (1933) and C. S. Rondestvedt, M. E. Rowley, J. AM. CHEM. SOC. 78, 3804 (1956).
The previously known processes have the following disadvantages. In most cases, the cleavage of the &bgr;-hydroxypropionic acids takes place incompletely with poor yields by weight. Only in a few cases, when the &bgr;-hydroxypropionic acids have aryl groups in the &agr;- and/or &bgr;-position, does the cleavage take place completely. In some cases, particularly when the &bgr;-hydroxypropionic acids have hydrogen atoms as substituents in the &agr;- and/or &bgr;-position, no cleavage occurs. The yield by weight, based on the carbonyl compounds formed during the cleavage, is therefore inevitably reduced in most cases.
Furthermore, the cleavage of the &bgr;-hydroxypropionic acids takes place in most cases very slowly and generally requires reaction times of more than 10 h, which makes the reaction very uneconomical, particularly when carried out on an industrial scale, owing to the poor yields as a function of time.
In addition, on working up in an aqueous medium to obtain or isolate the carbonyl compounds of the general formula (2), the water-miscible 1-propanol or other alcohol solvent dissolves in the aqueous phase. For reasons of cost-efficiency and for reducing the amounts of waste, recovery of the solvent used from the aqueous phase (for example by extraction or distillation) is necessary, particularly when used on an industrial scale. Such recovery, however, is associated with considerable cost. In addition, the use of water-immiscible organic solvents, such as ethyl acetate or methyl tert-butyl ether as cosolvents to achieve better phase separation is necessary with the use of water-miscible solvents such as 1-propanol or other alcohols during work-up to obtain or isolate the carbonyl compounds of the general formula (2). These solvents must be recovered and must be freed from impurities by distillation before being reused, which likewise is associated with high cost.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an economical process which makes it possible to cleave &bgr;-hydroxycarboxylic acids and to obtain and to isolate, in high yields and purities, the carbonyl compounds formed in the cleavage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The invention relates to a process for the preparation of a carbonyl compound of the general formula (1)
 R
1
R
2
C═O  (1),
in which a &bgr;-hydroxycarboxylic acid or its salt of the general formula (2)
R
1
R
2
C(OH)—CR
3
R
4
—COOM  (2)
is cleaved in the presence of a Brönstedt base which is selected from hydroxides, alkanolates, oxides, amides, and hydrides of the alkali metals and alkaline earth metals, and a hydroxyl-free solvent, where
R
1
denotes an optionally halogen- or cyano-substituted C
1
-C
30
-hydrocarbon radical in which one or more, non-neighboring methylene units may be replaced by groups —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR
x
— and in which one or more, non-neighboring methine units may be replaced by groups —N═, —N═N— or —P═,
R
2
denotes hydrogen or an optionally halogen- or cyano-substituted C
1
-C
30
-hydrocarbon radical in which one or more, non-neighboring methylene units may be replaced by groups —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR
x
— and in which one or more, non-neighboring methine units may be replaced by groups —N═, —N═N— or —P═,
R
3
and R
4
denote hydrogen, halogen or an optionally halogen- or cyano-substituted C
1
-C
30
-hydrocarbon radical in which one or more, non-neighboring methylene units may be replaced by groups —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR
x
— and in which one or more, non-neighboring methine units may be replaced by groups —N═, —N═N— or —P═,
R
x
denotes hydrogen or an optionally halogen- or cyano-substituted C
1
-C
30
-hydrocarbon radical in which one or more, non-neighboring methylene units may be replaced by groups —O—, —CO—, —COO—, —OCO— or —OCOO—, —S—, —NH— or —N—C
1
-C
20
-alkyl and in which one or more, non-neighboring methine units may be replaced by groups —N═, —N═N— or —P═, and
M denotes hydrogen, an alkali metal ion, an alkaline earth metal ion, or an ammonium ion,
where in each case 2 radicals which are selected from the pairs R
1
and R
2
, R
3
and R
4
and R
1
and R
3
can be linked to one another to form a cyclic structure.
The process is a retroaldolization. Carbonyl compounds of the general formula (2) can be obtained by the process in very high yields of up to or greater than 90% and in very high purities, in a simple manner, and simultaneously with very good space-time yields and hence high cost-efficiency.
The C
1
-C
30
-hydrocarbon radicals for R
1
, R
2
, R
3
and R
4
are preferably linear, branched or cyclic C
1
-C
20
-alkyl, C
3
-C
20
-alkoxycarbonylalkyl, C
2
-C
20
-alkenyl, C
5
-C
20
-acetalalkenyl or C
3
-C
20
-alkylcarbonyloxyalkyl radicals which may be substituted by F, Cl, Br, I, CN and C
1
-C
8
-alkoxy radicals and in which methylene units may be replaced by —O—, —S—, —NH— or —N—C
1
-C
20
-alkyl; aryl, aralkyl, alkaryl, aralkenyl or alkenylaryl radicals in which one or more methine units may be replaced by groups —N—, —N═N— or —P═, and methylene units by —O—, —S—, —NH— or —N—C
1
-C
20
-alkyl, and which may be substituted by F, Cl, Br, I, CN and C
1
-C
10
-alkoxy radicals and on the ring by C
1
-C
10
-alkyl radicals.
The halogen radicals R
3
and R
4
are preferably F and Cl.
The C
1
-C
20
-alkyl radicals for —N—C
1
-C
20
-alkyl in the meanings of R
x
may be branched, straight-chain or cyclic. Linear C
1
-C
10
-alkyl radicals are preferred.
The &bgr;-hydroxycarboxylic acids of the general formula (2) or their salts are used in the form of liquids or solids, optionally dissolved in a hydroxyl-free solvent.
Preferred hydroxyl-free solvents are aprotic solvents, in particular ethers, hydrocarbons and hydrocarbon-substituted silanes and siloxanes. Suitable ethers are mono- and polyethers, preferably symmetrical and asymmetrical di-C
1
-C
10
-hydrocarbon ethers, for example dibutyl ether, tetrahydrofuran, dihexyl ether, diphenyl ether, anisole or phenetole, or cyclic ethers, such as coumarone and tetrahydrofuran. Examples of polyethers are polyethylene glycol dimethyl ether and polyethylene glycol diethyl ether.
Preferred aromatic or aliphatic hydrocarbons are C
1
-C
20
-hydrocarbons and mixtures thereof, such as toluene, ethylbenzene, propylbenzene, isopropylbenzene, butylbenzene, xylene, xylene isomer mixtures, trimethylbenzene, octane, isooctane, nonane, nonane fractions, cycloheptane, cyclooctane, dimethylcyclohexane, ethylcyclohexane, propylcyclohexane, butylcyclohexane, petroleum benzine, and paraffin.
Hydrocarbon-substituted silanes and siloxanes are hydrocarbons in which one or more methylene groups may also be replaced by dialkylsilyl or dialkylsilyloxy groups. Preferred examples are tetraethylsilane, tetrapropylsilane, tetrabutylsilane, dimethyldiphenylsilane and polydimethylsiloxane.
Solvents or solvent mixtures having a boiling point or boiling range of up to 250° C. at 0.1 MPa are preferred.
Particularly suitable Brönstedt bases are the hydroxides

Affiliated with

Also associated with

Rating

Process for the preparation of carbonyl compounds by... 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 the preparation of carbonyl compounds by..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of carbonyl compounds by... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3012333