Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1998-06-02
2001-05-08
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S367000, C568S379000
Reexamination Certificate
active
06229051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the preparation of alkyl and aromatic ketones, aldehydes, or carboxylic acids. More preferably, the invention relates to a process for preparing aromatic ketones.
2. Description of the Related Art
Aromatic ketones are important synthetic intermediates for a number of valuable chemical compounds such as herbicides. Several such compounds are isoxazole and derivatives thereof (Cain et al.,
Euro. Pat. App. EP
470856 (1992)). These types of ketones are normally prepared by the Friedel-Crafts acylation of an aromatic nucleus. However, in some cases this methodology does not produce the desired isomer, and more indirect methods must be employed.
Conversion of nitro groups to the corresponding carbonyl can be achieved under Nef reaction conditions known in the art. For example, the preparation of aromatic ketones by an oxidative Nef reaction has been previously reported. Such aromatic ketones are shown to be useful as synthetic intermediates in the preparation of chemical pharmaceuticals. (Reid et al.,
Tetrahedron Lett
. 31:1093 (1990)). Classic Nef reactions are performed by adding a solution of a nitronate anion to a strongly acidic aqueous solution. However, these conditions achieve only minimal conversion of the nitro group of a nitronate anion substituted on an aromatic ring to the corresponding ketone. Conversion to the desired ketone can be achieved under oxidative Nef reaction conditions. However, a large excess of hydrogen peroxide, which is economically unattractive and potentially hazardous, is necessary. (Olah et al.,
Synthesis
662 (1980)).
Other means by which an oxidative Nef reaction may be achieved include the use of potassium permanganate, ammonium/sodium persulfate, or t-butylhydroperoxide with VO(AcAc)
2
. However each of these suffers from several drawbacks. Potassium permanganate has low solubility and its use produces large amounts of manganese dioxide as a by-product which makes product isolation difficult. (Reid et al.,
Tertahedron Lett
. 31:1093 (1990); Schechter et al.,
J. Org. Chem
. 27:3699 (1962)). An oxidative reaction using ammonium/sodium persulfate not only requires a large amount of the reagent but is quite sluggish and does not go to completion. (Pagano et al.,
J. Org. Chem
., 35:295 (1970)). The use of t-butylhydroperoxide with VO(AcAc)
2
gives very poor yields. (Bartlett et al.,
Tertahedron Lett
. 4:331 (1977)).
Accordingly, there exists a need in the art for an efficient and cost-effective process for preparing aromatic ketones.
SUMMARY OF THE INVENTION
The invention provides a straightforward, efficient and cost-effective process for the oxidation of a nitro functional group of an organic compound to a carbonyl functional group on the organic compound in the presence of a catalyst.
The invention also provides a straightforward, efficient and cost-effective process for the oxidation of nitro functional organic compound having the following general formula (I):
R
1
R
2
—CH—NO
2
(I)
The invention also provides a straightforward, efficient and cost-effective process for the oxidation of a nitroalkyl arene compound to an aromatic ketone in the presence of a catalyst.
The invention further provides a straightforward, efficient and cost-effective process for the oxidation a nitroalkyl nitroarene compound of the general formula (III):
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the invention is a process for the oxidation of a nitro functional group of an organic compound to a carbonyl functional group on the organic compound in the presence of a catalyst. This process, along with preferred embodiments, is described in more detail in the following discussion and examples.
The process involves oxidizing, via a catalyzed oxidative Nef reaction, an organic compound having a nitro functional group, such as, for example, an organic compound of the formula (I):
R
1
R
2
—CH—NO
2
(I)
In formula (I), R
1
and R
2
are, independently, hydrogen, a substituted or unsubstituted C
1
-C
10
alkyl, C
6
-C
10
aryl or C
4
-C
10
heteroaryl group or R
1
and R
2
together form a substituted or unsubstituted C
3
-C
7
cycloalkyl group. The alkyl group may be straight chain or branched. Preferably, the alkyl group is a methyl, ethyl, propyl or hexyl group. Preferably the cycloalkyl group is a cyclohexyl group. Preferably, the aryl or heteroaryl group is a phenyl, furanyl, pyrrolyl, isopyrrolyl, thienyl, napthyl, pyridinyl, pyranyl, or benzyl group. The alkyl, cycloalkyl, aryl and heteroaryl group, each as described above, may be substituted or unsubstituted. Suitable substituents include alkyl, aryl, heteroaryl, ether, thioether, halo, nitro, and other similar groups. Preferably, at least one of R
1
and R
2
is a hydrogen and the other is a methyl, ethyl or hexyl group. According to the invention, an organic compound of the formula (I) may not be nitrohexane.
Upon oxidation of an organic compound of formula (I), HNO
2
is in effect lost. Accordingly, depending upon R
1
and R
2
, oxidation of an organic compound of formula (I) may produce either an aldehyde or a ketone. Further oxidation of the aldehyde to the corresponding carboxylic acid may also be possible.
The oxidative Nef reaction may be conducted in a single phase aqueous alkaline solution system or in a single phase aqueous alkaline solution and water-miscible organic solvent system. Alternatively, the oxidative Nef reaction may be conducted in a biphasic system of an aqueous alkaline solution and a water-immiscible organic solvent. Preferably the oxidative Nef reaction is conducted is a biphasic system of an aqueous alkaline solution and a water-immiscible organic solvent.
The aqueous alkaline solution may be an aqueous solution of an alkali or alkaline earth metal carbonate or bicarbonate. Such a solution may be formed in situ. Preferably, the aqueous alkaline solution is an aqueous solution of Potassium Sodium carbonate (KNaCO
3
). More preferably, the aqueous alkaline solution is an aqueous solution of potassium carbonate and/or potassium bicarbonate, most preferably, potassium carbonate. After completion of oxidation of an organic compound of formula (I) as described above, the aqueous alkaline solution may be recycled for use in a subsequent oxidative Nef reaction. Recycling less than the entire aqueous alkaline solution is preferred for handling purposes and to avoid substantially increasing the overall reaction volume. Preferably about 60-75% of the aqueous alkaline solution is recycled. To regenerate the alkali or alkaline earth metal carbonate, an alkali or alkaline earth metal hydroxide may be added to the recycled solution. Fresh alkali or alkaline earth metal carbonate or bicarbonate may also be added as necessary to increase the amount of alkali or alkaline earth metal carbonate or bicarbonate to the desired level. If desired, additional amounts of catalyst, as described below, may be added.
Examples of suitable water-miscible organic solvents include, but are not limited to, acetone, dimethylsulfoxide (DMSO), tetrahydrofuran (THF), N-methyl pyrrolidone (NMP), dimethylformamide (DMF) and the like. Mixtures of these solvents may also be used. In the event that DMSO is used, the catalyst, as described below, may not be one or a mixture of the following: Mn(II), Mn(VII), Co(II), and tetrabutylammonium bromide (TBAB). Examples of suitable water-immiscible organic solvent include, but are not limited to, toluene, chlorobenzene, heptane and mixtures of such solvents. Preferably the water-immiscible organic solvent is toluene. Preferably, the organic solvent is the solvent used to obtain and/or isolate the nitro compound (I).
The oxidation may be accomplished using any oxidant or mixture of oxidants known in the art. Examples of the oxidant include, but are not limited to, hydrogen peroxide, t-butyl hydroperoxide; ammonium persulfate; oxygen; permanganates, perborates such as, for example, sodium perborate; percarbonates such as, for example, sodium percarbona
Blake Esq. Michael J.
Eastman Chemical Company
Gwinnell Harry J.
Wilson James O.
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