Diphosphines

Details Diphosphines Diphosphines

2002-08-15

2003-05-20

Vollano, Jean F. (Department: 1621)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Organic compound containing

C556S013000, C549S216000, C548S402000

Reexamination Certificate

active

06566298

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of racemic diphosphines, to a process for the preparation of enantiomerically pure diphosphines, to novel enantiomerically pure diphosphines, to novel intermediates for the preparation of diphosphines, and to catalysts that contain novel diphosphines.
A process that differs greatly from the process according to the invention for the preparation of diphosphines is known from EP-A 749,973. According to this, if the intention is to prepare enantiomerically pure diphosphines, the racemate resolution is carried out at the stage of the phosphine oxides, i.e., for individual diphosphines separate racemate resolutions must be carried out. Compounds different from the compounds according to the invention are described in EP-A 104,375, EP-A 582,692, and EP-A 690,065. Racemate resolutions with N-benzylcinchonidinium chloride have hitherto been described only for dinaphthol compounds (Tetrahedron Lett. 36, 7991 (1995)).
SUMMARY OF THE INVENTION
Specifically, the present invention first relates to a process for the preparation of racemic diphosphines of the formula (I)
in which
R is C
6
-C
14
-aryl or C
4
-C
13
-heteroaryl containing 1 to 3 heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, wherein the aryl and heteroaryl radicals may optionally be substituted by halogen, C
1
-C
6
-alkyl, C
1
-C
6
-alkoxy, and/or trimethylsilyl, and
R
1
to R
4
, independently of one another, are each hydrogen, C
1
-C
10
-alkyl, C
1
-C
10
-alkoxy, F, Cl, or Br,
 comprising
(a) converting a phenol of the formula (II)
 in which R
1
to R
4
have the meanings given for formula (I), into the corresponding phenoxide using a base,
(b) reacting the phenoxide with dihalogenomethane to give a formaldehyde acetal of the formula (III)
 in which R
1
to R
4
have the meanings given for formula (I),
(c) intramolecularly oxidatively coupling the formaldehyde acetal of the formula (III) to give a cycloheptadiene of the formula (IV),
 in which R
1
to R
4
have the meanings given for formula (I),
(d) converting the cycloheptadiene of the formula (IV) by treatment with an acid into a biphenyidiol of the formula (V)
 in which R
1
to R
4
have the meanings given for formula (I),
(e) preparing the corresponding triflate from the biphenyidiol of the formula (V), and
(f) coupling the triflate with a secondary phosphine of the formula (VI)
HPR
2
  (VI),
 in which R has the meaning given for formula (I), with the addition of a base and in the presence of a palladium(0), palladium(II), nickel(0), and/or Ni(II) compound, thereby giving a compound of the formula (I).
DETAILED DESCRIPTION OF THE INVENTION
In the formulas (I) to (V), R
1
and R
2
are preferably hydrogen and R
3
and R
4
are preferably C
1
-C
5
-alkoxy, fluorine, or chlorine. In the formulas (I) and (VI), R is preferably phenyl, furyl, or 2—N—C
1
-C
6
-alkylpyrrolyl that may optionally be substituted by 1 to 3 substituents from the group consisting of fluorine, chlorine, C
1
-C
5
-alkyl, C
1
-C
6
-alkoxy, and trimethylsilyl. In the formulas (I) to (V), R
1
and R
2
are particularly preferably hydrogen, R
3
is particularly preferably chlorine, and R
4
is particularly preferably methoxy or ethoxy. In the formulas (I) and (VI), R is particularly preferably phenyl, 2-furyl, 2-N-methylpyrrolyl, 3,5-dimethylphenyl, 4-fluorophenyl, 4-tolyl, or 3,5-dimethoxyphenyl.
In the conversion of the phenol of the formula (II) into the corresponding phenoxide, the base that can be used is, for example, an alkali metal hydride, hydroxide, or carbonate. Preference is given to sodium hydride and potassium hydride. The base is preferably used in an amount of from 0.9 to 1.5 equivalents per mole of phenol of the formula (II). Here, it is possible to work in the presence of a solvent, e.g., in the presence of a dipolar-aprotic solvent, such as dimethylformamide, or an ether, such as diethyl ether, tetrahydrofuran, dioxane, or methyl tert-butyl ether.
Suitable reaction temperatures, particularly when alkali metal hydrides are used as base, are, for example, those in the range from −20 to +60° C. It is advantageous to carry out this stage under a protective gas atmosphere. The procedure may involve, for example, initially introducing the base together with the solvent and metering in the phenol of the formula (II) dissolved in the same solvent.
The phenoxide obtained does not need to be isolated. Particularly if the process has been carried out with stoichiometric amounts of alkali metal hydride as base, the reaction mixture that is present following reaction with the base can be further used directly.
In the reaction with the phenoxide it is possible to use, based on one mole of phenol of the formula (II) originally used, e.g., 0.4 to 0.7 mol of dihalogenomethane. Suitable reaction temperatures are, for example, those from 0 to 80° C., particularly those from 10 to 60° C. The reaction time for the reaction with the dihalogenomethane can be, for example, 8 to 40 hours. Suitable as dihalogenomethane is, for example, dichloromethane, dibromomethane, and diiodomethane. Diiodomethane is preferred.
The reaction mixture that is then present can be worked up, for example, by extracting it after addition of water with a virtually nonpolar or nonpolar organic solvent and removing the solvent from the extract. The residue that remains can, if desired, be further purified, for example, by dissolving it in an ether, in methanol, or in acetonitrile at elevated temperature, discarding the insoluble components, and obtaining the prepared formaldehyde acetal of the formula (III) in purified form by crystallization.
The intramolecular oxidative coupling for the preparation of a cycloheptadiene of the formula (IV) can be carried out, for example, by first adding an organolithium compound to the formaldehyde acetal of the formula (III) and, when they have finished reacting, adding an oxidizing agent. For example, it is possible to add butyllithium dissolved in, for example, a hydrocarbon to a solution of the formaldehyde acetal, for example in ether, at −30 to +40° C. and leave the mixture to fully react by after-stirring at a temperature in this range. Per mole of formaldehyde acetal, it is possible to use, for example, 2.0 to 2.2 mol of organolithium compound. In general, the reaction is complete after 5 to 30 hours. The oxidizing agent can then be added, for example a Cu(II), Fe(III), Mn(III), or Ce(IV) compound. The oxidative coupling can also be carried out enzymatically, e.g., with a peroxidase. The oxidizing agent is added at, for example, −70 to −30° C., and the mixture is subsequently warmed to a temperature of, for example, below 50° C. Based on 1 mol of formaldehyde acetal of the formula (III) used, it is possible to use, for example, 2.0 to 2.5 equivalents of an oxidizing agent. It is advantageous to continue to after-stir the reaction mixture in conclusion, e.g., for 1 to 5 hours.
It is also possible to carry out the oxidative coupling directly from the formaldehyde acetal of the formula (III) in accordance with the methods described here without converting said formaldehyde acetal into the Li salt beforehand.
It is advantageous at least to carry out the reaction with the organolithium compound under a protective gas atmosphere.
The treatment with an acid to convert a cycloheptadiene of the formula (IV) into a biphenyldiol of the formula (V) can be carried out, for example, with a strong mineral acid such as hydrochloric acid or sulfuric acid. For example, 5 to 15 equivalents of acid can be used per mole of cycloheptadiene of the formula (IV). The procedure is expediently carried out in the presence of a solvent, for example in the presence of an alcohol. The treatment with the acid can be carried out, for example, in a period of from 5 to 50 hours at temperatures of from 50 to 100° C. The reaction mixture can be worked up, for example, analogously to the procedure described above for the preparatio

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