Method for oxidizing alkanes and cycloalkanes with aldehydes...

Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing

Reexamination Certificate

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C568S322000, C568S344000, C568S357000, C568S389000, C568S392000, C568S741000, C568S771000, C568S802000, C568S910000

Reexamination Certificate

active

06482989

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to a method for oxidizing alkanes with oxygen in catalytically oxidizing reactions. In this specification, the alkanes include cycloalkanes In the present invention, the alkanes and the cycloalkanes include substituted alkanes and substituted cycloalkanes, respectively. Further, the cycloalkanes include condensed rings in which an aromatic ring is condensed with a cycloalkane ring at an ortho position.
2. Related Art Statement
In the fields of the organic chemistry and the industrial chemistry, the necessity for methods of introducing oxygen functional groups in alkanes has been increasing in recent years, and earlier development of effective oxygen-oxidizing reactions has been demanded.
Alcohols and ketones obtained by oxidizing alkanes can be used as building blocks and starting materials for medicines, chemical products and polymers as well as various functional materials.
Heretofore, an automatic oxidizing method which undergoes a free radial reaction in the presence of a cobalt-based catalyst is used as an industrial method for oxidizing alkanes with oxygen. However, such an automatic oxidizing method required high temperature and high pressure conditions to realize a sufficient oxidation speed, and further needed to suppress the conversion rate at a low level to selectively obtain intended alcohol and ketone. In order to solve such problems, an oxygen-oxidizing method which is based on a new principle with use of a gentle condition of an oxygen pressure of 1 atm has been strongly demanded.
Under the circumstances, various examinations have been effected with respect to the oxidation of hydrocarbons with oxygen with use of the gentle condition of 1 atm. For example, one equivalent or more reducing agent is used for oxidizing a hydrocarbon with oxygen at 1 atm. As the reducing agent, zinc (J. Chem. Soc., Perkin. Trans. 1 1986, 947; J. C hem. Soc., Chem. Commun. 1991, 102; New J. Chem. 16, 621 (1992)), hydrazine (J. Am. Chem. Soc. 112, 879 (1990)), hydrogen (J. Am. Chem. Soc. 103, 7371 (1981); J. Am. Chem. Soc. 109, 2837 (1987); J. Chem. Soc., Chem. Commun. 1992, 1446), hydrogen sulfide (Chem. commun. 1997, 557), ascorbic acid salt (Tetrahedron 40, 4297 (1984)), hydroquinone (Chem. Lett. 1991, 1819), etc. were proposed. Each of the above reacting systems has a problem in that the yield of the product and the turnover number of the catalyst are low.
On the other hand, the present inventors discovered a method of oxygen-oxidizing alkanes with use of aldehydes in the presence of a copper/crown ether catalyst or a copper/crown ether/inorganic salt catalyst (JP-A 6-263,664 and JP-A 11-255,682). Although this method enables the alkane to be oxidized with use of oxygen at 1 atm, it has been demanded to construct an inexpensive catalyst system having further improved catalytic activity (turnover number) and substituting for crown ethers.
SUMMARY OF THE INVENTION
The present inventors made further investigations to improve the catalytic activity with due consideration of economy, and discovered that the catalytic activity is greatly improved by coordinating a nitrogen-containing compound such as a nitrile into a copper catalyst. The inventors reached the present invention based on this discovery. That is, the present invention is to provide a method for oxidizing an alkane and a cycloalkane with oxygen in the presence of an aldehyde, a copper catalyst and a nitrogen-containing material as an auxiliary ligand. In the present claims, the alkane includes the cycloalkane.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention will be described in more detail. (1) Alkanes
Specific examples of the alkanes and the cycloalkanes to be used in the oxidizing method of the present invention are given below.
(1-1) Alkanes
As the alkanes, represented by a general formula C
n
H
2n+2
(n=1 to 30), n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, etc. may be recited, for example. In the present invention, the alkane includes the substituted alkane represented by a general formula C
n
H
2n+1
R in which n=1 to 30, R denotes a carboxylic group, an ester group, a halogen group, a nitro group, a methoxy group, or an alkyl group or an aromatic group which may be substituted by a carboxylic group, an ester group, a halogen group, a nitro group or a methoxy group are included. As representative examples of the alkanes, mention may be made of toluene, p-xylene, m-xylene, o-xylene, 4-methoxytoluene, 3-methoxytoluene, 2-methoxytoluene, 4-chlorotoluene, 3-chlorotoluene, 2-chlorotoluene, ethylbenzene, diphenylmethane, 4-nitrotoluene, decanoic acid, methyl decanate.
(1-2) Cycloalkanes
The cycloalkane, which may be represented by a general formula C
n
H
2n
(n=5 to 30), and mention may be made of cyclohexane, cyclopentane, cyclooctane, cycloheptane, cyclododecane, etc. In the present invention, the cycloalkane may include a cycloalkane represented by a general formula C
n
H
2n-1
R in which n=5 to 30, R denotes a carboxylic group, an ester group, a halogen group, a nitro group, a methoxy group, or an alkyl group or an aromatic group which may be substituted by a carboxylic group, an ester group, a halogen group, a nitro group or a methoxy group. As examples of the cycloalkanes, mention may be made of methylcyclohexane, adamantane, cis-decalin, trans-decalin, cyclohexane carboxylic acid, cyclohexane carboxylic acid, methylchlorocyclohexane, nitrocyclohexane, etc. The cycloalkanes include a condensed ring in which an aromatic ring and a cycloalkane ring are condensed at an ortho position. As examples thereof, indane, 5, 6-dimethoxyindane, tetralin, fluorene, etc. may be recited.
(2) Copper-based Catalysts
As copper-based catalysts to be used in the present invention, conventionally known inorganic copper salts may be employed. For example, Cu(OAc)
2
-nH
2
O, Cu(OAc), Cu(OCOCF
3
)
2
, CuCN, CuCl, CUCl
2
-nH
2
O, CuBr, CuBr
2
, CuSO
4
-nH
2
O, Cu(NO
3
)
2
-nH
2
O, Cu(ClO
4
)
2
, Cu(OCH
3
)
2
, Cu(PO
4
)
2
-nH
2
O, CuO, Cu
2
O, Cu(acac)
2
, Cu(OH)
2
, Cu powder, etc. in which n is an integer of 0 to 6. In addition, copper coordination compounds which is preliminarily replaced by a nitrogen-series ligand, and peroxo crosslinked binuclear copper complexes easily formed therefrom in the presence of oxygen may be employed. For example, mention may be made of X, X (C
5
H
5
N: pyridine), X (bpy=2, 2′-bipyridine), X
2
(C
3
H
4
N
2
: imidazole), X
2
(phen=1, 10-phenanthroline), X
2
(C
14
H
32
N
4
=1, 4, 8, 11-tetramethyl-1, 4, 8, 11-tetraazacyclotetradecane), X (tmpa =tris(2-pyridylmethyl)amine), X, X
2
, X in which X, X are Cl, NO
3
, ClO
4
, PF
6
, BF
4
or the like. Among them, Cu(OAc)
2
which is easily available and handled and has high reactivity is preferably used. The use amount of the copper-based catalyst is not particularly limited, but it is ordinarily in a range of 0.000001 to 200 mol %, preferably in a range of 0.00001 to 5 mol % relative to a substrate.
(3) Aldehydes
As the aldehydes to be used in the present invention, aliphatic aldehydes and aromatic aldehydes may be employed. More specifically, mention may be made of aliphatic aldehydes such as acetaldehyde, propionaldehyde, n-butylaldehyde, isobutylaldehyde, n-valeraldehyde, isovaleraldehyde, pivalaldehyde, n-hexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, etc., substituted or non-substituted aromatic aldehydes such as benzaldehyde, p-chlorobenzaldehyde, m-chlorobenzaldehyde, m-cyanobenzaldehyde, p-tolualdehyde, p-methoxybenzaldehyde, etc, and mixtures of the above aldehydes. Among them, acetaldehyde which is easily industrially available is preferably employed from the standpoint of reactivity and economy. The use amount of the aldehyde is not particularly limited, but it is ordinarily in a range of 0.1 to 1000 mol %, preferably in a range of 1 to 400 mol % relative to the substrate.
(4) Nitrogen-containing c

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