Process for the preparation of six-membered ring carbocycles

Details Process for the preparation of six-membered ring carbocycles Process for the preparation of six-membered ring carbocycles

1999-02-22

2001-07-03

Killos, Paul J. (Department: 1623)

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

Organic compounds

Amino nitrogen containing

C585S269000, C585S270000

Reexamination Certificate

active

06255530

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of six-membered ring carbocycles by ring hydrogenation of aromatic compounds using hydrogen, the process being carried out in a reaction system consisting of two liquid, immiscible phases, of which the first phase is formed by the aromatic compound and, if necessary, a water-immiscible solvent, and the second phase consists of water, and, colloidally dispersed therein, a hydrogenation-active metal as hydrogenation catalyst, and auxiliaries for stabilizing the colloidal catalyst. Six-membered ring carbocycles of the type which can be prepared according to the invention are intermediates, known to the person skilled in the art, for the preparation of active ingredients and industrial chemicals.
It is already known to prepare six-membered ring carbocycles by ring hydrogenation of aromatic compounds. The hydrogenation is generally carried out using catalytically activated hydrogen; the hydrogenation-active metals suitable for this purpose are known and are generally those from the group of platinum metals and also nickel, chromium, niobium or copper. Although catalytic hydrogenations in the homogeneous phase are characterized by low diffusion inhibition, they are also characterized by the difficulty in separating the reaction product off from the reaction mixture and thus from the homogeneously dissolved catalyst by distillation, crystallization or other methods. The activity of the hydrogenation catalyst frequently also suffers at the same time. Use of slurried catalyst in the slurry phase partly overcomes the difficulty of separation although the need for coarse and fine filtration remains. There does however remain the risk of deactivating the catalyst, and a new difficulty arises, namely that of erosion in pumps, piping, valves and other parts of the apparatus by the catalyst to be removed. Difficulties of the last-mentioned type are overcome by arranging the catalyst in the form of a fixed bed in the reaction apparatus and allowing the reaction material in the liquid phase (e.g. trickle phase) or in the gas phase to flow over the catalyst. However, this reaction method, which has been perfected to a high degree, is only suitable for reactions with large throughputs. In the case of products which are prepared in small amounts and often only in batches, to carry out the reaction using catalysts in the form of a fixed bed is too complex.
DE-A 44 43 705 discloses the hydrogenation of benzene on a sulfobetaine-stabilized, colloidal catalyst comprising Ru on a La
2
O
3
support to give cyclohexane; at 50 bar and 150° C., only 8.5% conversion and 78.5% selectivity were achieved in 0.5 h. According to Tetrahedron Letters 1983, 4139-42, the hydrogenation results deteriorate severely in the case of substituted benzenes. WO 96/08462 discloses the catalytic hydrogenation of aromatic amines to cyclohexylamines using hydrogen on an Ru/Al
2
O
3
catalyst in the presence of LiOH, which is said to prevent deamination; the reaction medium is a water-containing water-miscible organic solvent.
SUMMARY OF THE INVENTION
It has now been found that it is possible to prepare six-membered ring carbocycles by ring hydrogenation of the corresponding aromatic compounds using a catalyst arranged in a different phase, the reaction mixture on the one hand and the hydrogenation catalyst in colloidal form on the other hand being arranged in two immiscible liquid phases. The process according to the invention is highly suitable for carrying out ring hydrogenations of aromatic compounds batchwise, although it can also be carried out continuously in a mixer/settler procedure known to the person skilled in the art.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a process for the preparation of six-membered ring carbocycles of the formula (II) by ring hydrogenation of aromatic compounds of the formula (I)
where, in the formulae,
R
1
, R
2
and R
3
independently of one another are hydrogen, straight-chain or branched C
1
-C
18
-alkyl, straight-chain or branched C
2
-C
18
-alkenyl, C
3
-C
8
-cycloalkyl, straight-chain or branched C
1
-C
18
-alkoxy, amino, nitro, hydroxyl, fluoro, cyano, —(C
0
-C
4
-alkanediyl)-COO—(C
0
-C
4
-alkyl), —(C
2
-C
4
-alkenediyl)-COO—(C
0
-C
4
-alkyl), —(C
0
-C
4
-alkanediyl)-C
6
-C
12
-aryl), —O—CO—(C
1
-C
18
-alkyl), —O—(C
6
-C
12
-aryl), —CO—(C
1
-C
18
-alkyl), —CO—(C
6
-C
12
-aryl), —S—(C
6
-C
12
-aryl), —NH—(C
1
-C
18
-alkyl), —N(C
1
-C
18
-alkyl)(C
1
-C
4
-alkyl), —NH—(C
6
-C
12
-aryl), —N(C
6
-C
12
-aryl)(C
1
-C
4
-alkyl) or —P(X)
m
(Y)
n
(Z)
q
(═O)
r
, where X, Y and Z independently of one another are phenyl or C
1
-C
4
-alkyl, and Y and Z additionally and independently of one another may be OR
4
or NR
4
2
, where R
4
is phenyl, C
1
-C
4
-alkoxy or C
1
-C
4
-alkyl, and NR
4
2
can also be piperidino, and Y and Z together can also be —O—CH
2
CH
2
—O—, and the bracketed term represents double-bonded oxygen, m is zero, one or two, and n, q and r independently of one another are zero or one, the sum m+n+q+r corresponding to the valency of phosphorus, where aryl constituents may be mono- or disubstituted by C
1
-C
4
-alkyl, C
1
-C
4
-alkoxy, amino, nitro, hydroxyl or mixtures thereof, and where in addition two of the radicals R
1
, R
2
and R
3
, if they are adjacent, can together be the radical of a fused benzene or 1,2-naphthalene or 2,3-naphthalene system, trimethylene, tetramethylene or propenediyl, each of which may be substituted like the aryl constituents above, and
R
1′
, R
2′
and R
3′
independently of one another are as defined for R
1
, R
2
and R
3
, with the proviso that olefinically unsaturated constituents in R
1
, R
2
and R
3
can form the corresponding saturated constituents, nitro can form amino, CO can form CHOH or CH
2
and cyano can form aminomethyl,
which is characterized in that the hydrogenation is carried out at from 50 to 180° C. and from 1 bar to 400 bar in a reaction system consisting of two liquid, immiscible phases in which elemental hydrogen is dispersed, the first phase being formed by the aromatic compound and, if necessary, a water-immiscible solvent, and the second phase consisting of water, and, colloidally dispersed therein, a hydrogenation-active metal from groups Ib and VIII of the Periodic Table of the Elements (Mendeleev) as hydrogenation catalyst, and auxiliaries for stabilizing the colloidal catalyst, and in the presence of from 100 to 2000% of the stoichiometrically necessary amount of hydrogen.
Examples of straight-chain or branched C
1
-C
18
-alkyl are methyl, ethyl, propyl, isopropyl, butyl isobutyl, the isomeric pentyls, hexyls, heptyls, octyls, decyls, dodecyls, hexadecyls and octadecyls. Straight-chain or branched C
2
-C
18
-alkenyl is derived from the corresponding alkyl such that an olefinic double bond is present; it may be internal or terminal. Straight-chain or branched C
1
-C
18
-alkoxy is derived from the corresponding alkyl such that the alkyl is bonded via an ether oxygen atom.
In preferred terms, alkyl and alkoxy have from 1 to 12 carbon atoms and alkenyl has from 2 to 12 carbon atoms. In particularly preferred terms, alkyl and alkoxy have from 1 to 4 carbon atoms; with particular preference, alkenyl has from 2 to 4 carbon atoms.
Examples of cycloalkyl are cyclopropyl, cyclobutyl, cyclopentyl, methyl-cyclopentyl, dimethyl-cyclopentyl, cyclohexyl, methyl-cyclohexyl, dimethyl-cyclohexyl, cycloheptyl or cyclooctyl. Cycloalkyl is preferably cyclopropyl, cyclopentyl or cyclohexyl.
The group C
0
-C
4
-alkanediyl is a spacer group and is accordingly divalent. It may, however, degenerate to a single bond, which is characterized by the expression C
0
(no carbon atoms). By complete analogy, the group C
0
-C
4
-alkyl is the alcoholic moiety of an ester group, where in the case of C
0
the ester group degenerates to the acid hydrogen atom (no carbon atoms). The group —(C
0
-C
4
-alkanediyl)-COO—(C
0
-C
4
-alkyl) can thus be the nonesterified carboxyl group —COOH if the two bracketed terms

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