Method for catalytic and selective oxidation of aromatic...

Details Method for catalytic and selective oxidation of aromatic... Method for catalytic and selective oxidation of aromatic...

2000-03-14

2002-04-02

Nazario-Gonzalez, Porfirio (Department: 1621)

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

Organic compounds

Cyclohexadiene having atoms double bonded directly at the 1-...

C552S299000, C568S741000, C502S167000, C556S047000

Reexamination Certificate

active

06365762

ABSTRACT:

The present invention relates to the use of Re catalyst systems for the oxidation of electron-rich aromatic compounds, the catalyst system having not only an extended useful life but also excellent activity, and to a process for the oxidation of electron-rich aromatic compounds using this catalyst system.
Oxidative processes play a crucial part in organic synthesis. Numerous basic and fine chemicals are prepared using atmospheric oxygen, hydrogen peroxide and alkyl peroxides. In most cases, the reactions are efficient and selective only if the oxidizing agents are used in the presence of catalysts. In practice, these are mostly metal oxides such as, for example, V
2
O
5
, CrO
3
, MoO
3
, WO
3
, OsO
4
and RuO
4
, which are employed, for example, in epoxidation, hydroxylation or carboxylation reactions (Catalytic Oxidations with Hydrogen Peroxide as Oxidant (Ed.: G. Strukul), Kiuwer, Dordrecht, 1992, 13-43; H. A. Jørgensen, Chem. Rev. 1989, Vol. 98, pp. 431-458).
Application of such systems to the catalytic oxidation of aromatic compounds is not self-evident: lack of activity (WO
3
) on the one hand, deficient selectivity on the other hand (CrO
3
/H
2
SO
4
), tendency to catalytic decomposition of hydrogen peroxide (RuCl
3
), besides the frequent lack of acceptability in ecological and health terms (for example in the case of OsO
4
or CrO
3
), which result in complicated and costly disposal, have to date prevented the use of such catalysts.
Other processes already established in oxidation chemistry and employing, for example, electrochemical oxidation, cerium(IV) salts, manganese(III) sulfate or peroxides (tBuOOH) in the presence of molybdenum complexes as oxidizing agents prove in the oxidation of simple or fused aromatic compounds and their derivatives to be complicated and costly, and are often associated, owing to the need to employ stoichiometric amounts (cerium(IV) salts, manganese(III) sulfate), with high salt burdens and are usually also nonspecific (R. P. Kreh et al., J. Org. Chem., 1989, 54, 1526-1531; M. Hudlicky, Oxidations in Organic Chemistry, ACS Monograph 186, Washington D.C. 1990, pp. 92-98; T. A. Gorodetskaya et al. U.S.S.R. Patent 1 121 255, 1984; Chem. Abstr., 1985, 102, 203754; W. Adam et. al., Synthesis, 1993, 280-282, J. Skarzewski, Tetrahedron, 1984, 40, 4997-5000; S. Yamaguchi et al., Bull. Chem. Soc. Jpn. 1986, 59, 2881-2884; M. Perisamy, M. V. Bhatt, Tetrahedron Lett. 1978, 4561-4562, Y. Asakawa et al., 1988, J. Org. Chem., 53, 5452-5457; W. Chen, Chem. Abstr., 1987, 107, 58620).
EP 0665209 A1 and EP 0686618 A1 disclose organorhenium compounds of the general type R
1
a
Re
b
O
c
.L
d
(L=Lewis base) which are employed as catalysts for oxidizing a large number of aromatic compounds to quinoid systems in the presence of hydrogen peroxide.
These rhenium compounds can be synthesized in a simple manner from commercially available Re
2
O
7
with the aid of conventional substances which act as donors of organic groups, for example in the case of R
1
=CH
3
by reaction with commercially available tetramethyltin or commercially available dimethylzinc. They are insensitive to air and moisture, can be stored at room temperature and are, in conjunction with peroxide-containing compounds such as, for example, hydrogen peroxide, suitable catalysts for oxidizing aromatic compounds. However, it has emerged that the useful life of the catalysts, especially at the elevated temperature which is normally necessary, is only inadequate.
The object therefore was to find a catalyst system which is, where possible, easily obtainable, low-cost, simple to handle, storable and effective and which, besides high selectivity in the oxidation of aromatic compounds, shows improved useful life of the catalyst and excellent activity.
It has now been found, surprisingly, that on addition of anhydrides of carboxylic acids to the reaction system in combination with peroxide-containing compounds there is a drastic increase in the catalytic activity of rhenium compounds. This results in a decisive improvement in the previously disclosed process and was by no means to be expected.
The invention therefore relates to the use of compounds of the formula
R
1
a
Re
b
O
c
.L
d
  (I),
in which
and the total of a, b and c is such as to comply with the pentavalency or heptavalency of rhenium, with the proviso that c is not larger than 3×b, and in which R
1
is absent or identical or different, and is an aliphatic hydrocarbon radical having 1 to 20 and preferably from 1 to 10 carbon atoms, an aromatic hydrocarbon radical having 6 to 20 and preferably from 6 to 10 carbon atoms or an arylalkyl radical having 7 to 20 and preferably from 7 to 9 carbon atoms, it being possible for the R
1
radicals where appropriate to be substituted identically or differently, independently of one another, and in the case of &dgr;-bonded radicals at least one hydrogen atom is still bonded to the carbon atom in the &agr; position, as catalysts for oxidizing electron-rich aromatic compounds and their derivatives in the presence of an anhydride of a carboxylic acid and of a peroxide-containing compound.
The invention further relates to a process for the oxidation of electron-rich aromatic compounds, which comprises oxidizing electron-rich C
6
-C
22
-aryl compounds and their derivatives in the presence of a catalyst of the formula R
1
a
Re
b
O
c
.L
d
(I), in which R
1
, a, b, c, d and L have the abovementioned meaning, of a peroxide-containing compound and of an anhydride of a carboxylic acid.
The compounds of the formula (I) can also be in the form of their Lewis base adducts. Typical examples of Lewis bases are pyridine, bipyridine, t-butylpyridine, amines, in particular secondary and tertiary amines such as triethylamine and quinuclidine, H
2
O and polyethers such as, for example, diglyme.
An aliphatic hydrocarbon radical R
1
means alkyl radicals having 1 to 20 and preferably from 1 to 10 carbon atoms, alkenyl or alkynyl radicals having 2 to 20 and preferably from 2 to 10 carbon atoms, cycloalkyl or cycloalkenyl radicals having 3 to 20 and preferably from 3 to 10 carbon atoms. Suitable examples of R
1
are alkyl radicals such as methyl, ethyl, propyl, isopropyl and the various butyl, pentyl, hexyl, octyl radicals such as ethylhexyl and decyl radicals, and alkenyl radicals such as allyl; also suitable are cycloalkyl radicals such as cyclopropyl, cyclobutyl, cyclopentyl, alkylated cyclohexyl such as hydrogenated tolyl, xylyl, ethylphenyl, cumyl or cymyl, 1-menthyl and 1-norbonyl, and alkenyl radicals such as vinyl and allyl and cycloalkenyl radicals such as cyclopentadienyl and pentamethylcyclopentadienyl.
Suitable examples of an aromatic hydrocarbon radical R
1
are phenyl or naphthyl. Benzyl may be mentioned as an example of an arylalkyl radical.
The radical R
1
can also be substituted. Examples of suitable substituents are fluorine, chlorine, bromine, NH
2
, NR
2
2
, PH
2
, PHR
2
, PR
2
2
, OH or OR
2
, where R
2
is identical or different and is an alkyl radical having 1 to 20 and preferably from 1 to 10 carbon atoms or an aryl radical having 6 to 20 and preferably from 6 to 10 carbon atoms, which may, for example, have the meanings stated above for R
1
.
Very particularly preferred compounds of the formula (I) are the rhenium oxides methylrhenium trioxide (CH
3
ReO
3
), cyclopentadienylrhenium trioxide (CpReO
3
), cyclopropylrhenium trioxide (C
3
H
5
ReO
3
) and dirhenium heptoxide (Re
2
O
7
).
It is essential to the invention that the reaction system comprises an anhydride of a carboxylic acid.
Particularly suitable anhydrides for the present invention are those of aliphatic carboxylic acids, with anhydrides of aliphatic carboxylic acids having 1-6 carbon atoms being preferred, and it also being possible for the carboxylic acid to be unsaturated and/or branched.
Suitable examples are, in particular, the anhydrides of acetic acid, propionic acid, n-butyric acid, n-valeric acid, n-caproic acid, i-butyric acid, i-valeric acid, ethylmethylacetic acid, trimethylacetic acid, propenoic acid,

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