Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2002-02-01
2004-04-13
Vollano, Jean F. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C546S023000
Reexamination Certificate
active
06720281
ABSTRACT:
The present invention relates to novel chiral phosphorus compounds which can be readily prepared from quinoline derivatives, and their use as catalysts or catalyst components in processes for the preparation of optically active products.
Chiral phosphorus compounds are of great interest as catalysts or catalyst components (“ligands”) for the enantioselective chemical synthesis of optically active products (Handbook of Enantioselective Catalysis with Transition Metal Compounds, Vol. II, VCH, Weinheim, 1993). Optically active products are of great economic importance as flavoring agents, cosmetics, plant protectants, food additives, pharmaceuticals, or in the preparation of high-tech materials, such as special plastics (Comprehensive Asymmetric Catalysis, Springer, Berlin, 1999). To date, despite of the wide variety of known chiral phosphorus compounds, only a few members have been put to use in industrial processes for the preparation of optically active products, because many ligands have serious disadvantages for technical applications. Many ligands, although exhibiting high enantioselectivities, form the desired chiral products with too low activities or insufficient chemo- or regioselectivities. Further, chiral phosphorus compounds which act as efficient ligands are often available only by tedious syntheses using expensive starting materials. In most efficient ligands, the chiral information which results in the selective formation of the optically active products is based on the use of chiral building blocks which are either derived from naturally occurring compounds or otherwise commercially available in an optically pure form. A structural variation in the chiral center for optimizing the phosphorus compound cannot be realized in a simple way in this case, and often only one of the two possible configurations is available. Therefore, there is a great need for novel chiral phosphorus compounds which can be synthesized in a simple and flexible way from readily available and inexpensive starting compounds and can be effectively employed as catalysts or catalyst components for the preparation of chiral products in various types of reaction.
The present invention relates to a novel class of chiral phosphorus compounds of general formula I
wherein R
1
, R
2
, R
3
1
, R
4
, R
5
are chiral or achiral organic residues which are derived from substituted or unsubstituted straight or branched chain or cyclic aliphatic or aromatic groups and which, in the case of the pairs R
1
/R
2
and R
4
/R
5
, may be interconnected. These compounds can be prepared simply and in few steps from derivatives of quinoline as inexpensive starting materials. The chiral information in the 2-position of the quinoline skeleton, which is critical to the selective formation of the desired optically active products, is produced during the synthesis and can be easily varied by selecting R
3
. The two isomers with the different configurations in the 2-position can be effectively separated from each other. The compounds of formula I can be employed as efficient catalysts or catalyst components in the preparation of optically active products, wherein high activities and selectivities are achieved especially in enantioselective hydroformylation and hydrogenation.
Synthesis of the Phosphorus Compounds I
The synthesis of the phosphorus compounds I (Scheme 1) conveniently starts from 8-phosphinoquinolines II. Compounds II are already known for different residues R
1
and R
2
and can be easily prepared on a multigram scale via different routes (typical examples: Inorg. Chem. 1982, 21, 1007; J. Organomet. Chem. 1997, 535, 183). By means of these syntheses and suitable simple modifications, compounds of type II can be prepared in which R
1
or R
2
are the same or different chiral or achiral organic residues which are derived from substituted or unsubstituted straight or branched chain or cyclic aliphatic or aromatic groups and may be interconnected. Residues R
1
and R
2
can be independently selected from the groups methyl, ethyl, n-propyl, n-butyl, hexyl, F(CF
2
)
m
(CH
2
)
n
— (m=1-10, n=0-4), cyclo-hexyl, menthyl, allyl, benzyl, CH
3
O(CH
2
)
2
OCH
2
—, phenyl, tolyl, anisyl, trifluoro-methylphenyl, F(CF
2
)
m
(CH
2
)
n
C
6
H
4
—(m=1-10, n=0-4), bis(trifluoromethyl)phenyl, chlorophenyl, pentafluorophenyl, hydroxyphenyl, carboxyphenyl, NaO
3
SC
6
H
4
—, naphthyl, fluorenyl, pyridyl or furyl, the groups mentioned not being intended to imply any limitation to the scope of application. When the two groups are interconnected, there may be formed substituted or unsubstituted chiral or achiral bridges which are derived, for example, from the skeletons —(CH
2
)
n
— (n=2-4), —CH(CH
3
)CH(CH
3
)—, —CH(CH
3
)CH
2
CH(CH
3
)—, 1,1′-bipheny-2,2′-diyl or 1,1′-binaphth-2,2′-diyl, again no limitation being implied by this listing.
The reaction of II with nucleophilic reagents R
3
M yields compounds III, wherein R
3
refers to the same definition as R
1
or R
2
. The addition in 2-position of the quinoline can be accomplished with Grignard compounds (M=MgHal, Hal=halogen) and many other organometallic compounds (e.g., M=Li, ZnR, SnR
3
; R=alkyl or aryl residue), so that a wide variety of possible derivatives results. The addition in 2-position of the quinoline produces a chiral center, the stereochemistry at this center not being defined in the absence of an additional chiral auxiliary or catalyst.
Compounds III can be converted to the 1,2-dihydroquinoline derivatives IV by hydrolysis. Reaction with chlorophosphinites (R
4
O)(R
5
O)PCI in the presence of bases such as triethylamine or pyridine yields the desired phosphorus compounds of formula I. An alternative approach is the reaction of III with PCI
3
to form the dichlorophosphine derivatives V. Reaction with alcohols or diols in the presence of base again yields I. Compounds III can also be reacted directly with chloro-phosphinites (R
4
O)(R
5
O)PCI without further addition of bases to I.
The residues R
4
and R
5
may be the same or different, achiral or chiral, and may be interconnected. Otherwise, the residues have the same definition as residues R
1
and R
2
. Examples of alcohols and diols which may be used for the preparation of the corresponding compounds (R
4
O)(R
5
O)PCI or directly reacted with V include methanol, ethanol, iso-propanol, benzyl alcohol, cyclohexanol, allyl alcohol, phenol, methylphenol, chlorophenol, naphthol, furfurol, ethylene glycol, 1,3-propanediol, 1,3-pentanediol, cyclohexanediol, glycerol, monosaccharides, oligosaccharides, catechol, 2,2′-dihydroxy-1,1′-biphenyl, 3,3′,5,5′-tetra-tert-butyl-2,2′-dihydroxy-1,1′-biphenyl,3,3′-di-tert-butyl-2,2′-dihydroxy-5,5′-dimethoxy-1,1′-biphenyl,5,5′-dichloro-4,4′,6,6′-tetramethyl-2,2′-dihydroxy-1,1′-biphenyl or 2,2′-dihydroxy-1,1′-binaphthyl, the listing not being intended to imply any limitation to the scope of application.
When optically active (R
4
O)(R
5
O)P groups are used, compounds I are obtained as diastereomers which can be separated by crystallization, chromatography or other suitable separation methods. Alternatively, the separation of the two stereoisomers can be effected on the stage of the 1,2-dihydroquinoline derivatives IV, which can be resolved by conventional methods into enantiomers IVa and IVb (see, for example, Tetrahedron Asymmetry 1999, 10, 1079).
Table 1 gives a survey about representative examples of compounds of formula I which were produced and spectroscopically characterized by the mentioned methods. A detailed description for the preparation of the mixture of diastereomers (R
a
,R
C
*)-quinaphos and the pure diastereomers (R
a
,R
C
)-quinaphos and (R
a
,S
C
)-quinaphos (quinaphos: R
1
=R
2
=Ph, R
3
=n-Bu, R
4
-R
5
=1,1′-binaphth-2,2′-diyl) can be found in Example 1. The assignment of an absolute configuration to the chiral center in the 2-position of th
Arena Carmela G.
Faraone Felice
Francio Giancarlo
Leitner Walter
Norris & McLaughlin & Marcus
Studiengesellschaft Kohle mbH
Vollano Jean F.
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