Process for the preparation of aldehydes

Details Process for the preparation of aldehydes Process for the preparation of aldehydes

2002-11-07

2004-06-22

Richter, Johann (Department: 1621)

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

Organic compounds

Oxygen containing

C568S451000, C568S452000

Reexamination Certificate

active

06753450

ABSTRACT:

The present invention relates to a process for the preparation of aldehydes in which at least one compound containing a vinyl or vinylidene group is reacted with carbon monoxide and hydrogen in the presence of a source of a metal from sub-group VIII and in the presence of a bidentate diphosphine ligand.
Hydroformylation or the oxo synthesis is an important large-scale industrial process and serves for the preparation of aldehydes by reaction of ethylenically unsaturated compounds with carbon monoxide and hydrogen. The reaction itself is highly exothermic and generally proceeds under superatmospheric pressure and at elevated temperatures in the presence of catalysts. The catalysts employed are usually metals from sub-group VIII of the Periodic Table of the Elements, in particular cobalt, rhodium, iridium, ruthenium, palladium or platinum compounds or complexes, which may have been modified by means of nitrogen- or phosphorus-containing ligands in order to influence the activity and/or selectivity.
In the case of asymmetrical ethylenically unsaturated compounds, the two possible orientations of the carbon monoxide adduction onto the C—C double bond give different aldehydes. In general, therefore, a mixture of isomeric aldehydes is obtained, as illustrated below.
The compound (1) is frequently known as n-aldehyde, and the compound (2) as iso-aldehyde.
Owing to the fact that the n-aldehydes are generally of significantly greater industrial importance than the isoaldehydes, it is an aim to optimize the hydroformylation catalysts and conditions in order to achieve the greatest possible n-selectivity, i.e. the highest possible ratio of n-aldehyde to isoaldehyde in the product aldehydes.
WO 98/42717 describes carbonylation reactions in the presence of a carbonylation catalyst containing a diphosphine, of which at least one phosphorus atom is part of a 2-phosphatricyclo[3.3.1.1{3,7}]decyl group. The carbonylation reactions described also include hydroformylations. Although WO 98/42717 indicates that, in order to prepare the catalyst system described therein, the ligand is generally employed in excess relative to the metal cation, nothing is stated regarding the amount of ligand present during the carbonylation reaction. In the hydroformylation examples in WO 98/42717, molar ratios between the diphosphine ligand and the rhodium metal of 1:1.2 (Example 9), 1:1 (Example 10) and 1:2 (Example 11) are used. In the hydroformylation of propene, an approximately equimolar mixture of butanal and 2-methylpropanal is obtained.
It is an object of the present invention to indicate a process with very high n-selectivity for the preparation of aldehydes by hydroformylation of compounds containing at least one vinyl or vinylidene group.
We have found that this object is achieved by a process for the preparation of aldehydes in which at least one compound containing a vinyl or vinylidene group is reacted with carbon monoxide and hydrogen in the presence of a source of a metal from sub-group VIII and in the presence of a bidentate diphosphine ligand, where the diphosphine ligand has the general formula I
in which
A together with the phosphorus atom to which it is bonded, in each case forms a 2-phosphatricyclo[3.3.1.1{3,7}]decyl radical, in which one or more non-adjacent carbon atoms may be replaced by oxygen atoms and which is substituted or unsubstituted, and
X is a bridging chain having 1 to 10 carbon atoms,
and the molar ratio between the diphosphine ligand and the metal is at least 5.
The molar ratio between the diphosphine ligand and the metal is in accordance with the invention at least 5, preferably at least 8 and in particular at least about 10. The molar ratio is generally less than about 50, usually less than about 20.
Tricyclo[3.3.1.1{3,7}]decane is also known by the trivial name “adamantane”. In the 2-phosphatricyclo[3.3.1.1{3,7}]decyl radical of the ligand used in accordance with the invention, one or more non-adjacent carbon atoms, which are preferably not adjacent to the phosphorus atom, may have been replaced by oxygen atoms. The carbon atoms in positions 6, 9 and 10 have preferably been replaced by oxygen atoms.
The 2-phosphatricyclo[3.3.1.1{3,7}]decyl radical may carry substituents on one or more of its carbon atoms. One or more carbon atoms in positions 1, 3, 5 and/or 7, in particular all carbon atoms in positions 1, 3, 5 and 7, preferably carry substituents, which are preferably identical. Examples of suitable substituents are alkyl, cycloalkyl, haloalkyl, aryl and aralkyl. The carbon atoms in positions 4 and/or 8 may carry one or two substituents, such as C
1
-C
4
-alkyl or halogen atoms, in particular fluorine atoms.
The two 2-phosphatricyclo[3.3.1.1{3,7}]decyl radicals present in the diphosphine ligands to be used in accordance with the invention may have identical or different substituents. Depending on the substitution pattern, the diphosphines may be in the form of diastereomers. In general, both the diastereomer mixtures and the pure diastereomers are suitable for the purposes according to the invention.
X is a bridging chain having 1 to 10 atoms, preferably 2 to 4 atoms, in particular 3 atoms. X is preferably a C
1
- to C
10
-alkylene bridge, which may have one, two, three or four double bonds and/or may be interrupted by one, two or three non-adjacent heteroatoms and/or may be fused to one, two or three saturated or unsaturated 3- to 7-membered carbocyclic or heterocyclic rings.
The fused unsaturated carbocyclic rings in radical X are preferably benzene or naphthalene, in particular benzene. Fused benzene rings are preferably unsubstituted or have 1, 2 or 3, in particular 1 or 2, substituents selected from alkyl, alkoxy, halogen, haloalkyl, nitro, carboxyl, alkoxycarbonyl and cyano. Fused saturated carbocyclic rings are preferably cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.
If the alkylene bridge in radical X is interrupted by heteroatoms, these are preferably selected from oxygen, sulfur and nitrogen.
Preferred radicals X are selected from
—(CH
2
)
x
—
where x is an integer from 1 to 10, preferably 2 to 4,
Y is O, S or NR
5
, where R
5
is alkyl, cycloalkyl or aryl,
or Y is a C
1
-C
3
-alkylene bridge, which may have a double bond and/or an alkyl, cycloalkyl or aryl substituent,
or Y is a C
2
-C
3
-alkylene bridge which is interrupted by O, S or NR
5
,
R
1
, R
2
, R
3
and R
4
, independently of one another, are hydrogen, alkyl, cycloalkyl, haloalkyl, aryl, alkoxy, aryloxy, aralkoxy, halogen, nitro, alkoxycarbonyl or cyano.
X is particularly preferably propylene.
A, together with the phosphorus atom to which it is bonded, is preferably a group of the general formula II
where the radicals R, independently of one another, are alkyl, cycloalkyl, haloalkyl, aryl or aralkyl.
For the purposes of the present invention, the terms used have the following meanings, unless stated otherwise:
“alkyl” means straight-chain or branched alkyl, preferably C
1
-C
20
-alkyl, in particular C
1
-C
8
-alkyl, particular preferably C
1
-C
4
-alkyl. Examples of alkyl groups are, in particular, methyl, ethyl, propyl, isopropyl, n-butyl, 2-butyl, s-butyl, t-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 2-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethylbutyl, 2-ethylbutyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-heptyl, 3-heptyl, 2-ethylpentyl, 1-propylbutyl and octyl;
“cycloalkyl” preferably means C
5
-C
7
-cycloalkyl, such as cyclopentyl, cyclohexyl or cycloheptyl;
“haloalkyl” preferably means C
1
-C
4
-haloalkyl, i.e. a C
1
-C
4
-alkyl radical which is partially or fully substituted by fluorine, chlorine, bromine and/or iodine, such as chloromethyl, dichloromethyl, trichloromethyl, fluoromethyl, difluoromethyl,

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