Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2002-06-18
2003-08-05
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C568S008000, C205S420000
Reexamination Certificate
active
06603032
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel bisphosphine compound having a chiral center on the phosphorus atom, which is useful as a ligand for asymmetric catalysts for use in asymmetric hydrogenation, and a process for the production of this bisphosphine compound, and further to a transition metal complex having this bisphosphine compound as a ligand, and a process for the asymmetric hydrogenation of an unsaturated carboxylic acid and its ester using this transition metal complex as an asymmetric catalyst for asymmetric hydrogenation.
BACKGROUND ART
Asymmetric catalytic synthesis is of great importance as the method for producing optically active fine chemicals that include agricultural products, pharmaceutical preparations and so on. An optically active phosphine ligand has played a major role as the ligand for transition metal complexes, and hence, a wide variety of related ligands have been reported to date. They are disclosed, for instance, in “Asymmetric Synthesis”, Vol. 5, authored by J. D. Morrison (published in 1985 by Academic Press Inc.), “Fundamentals and Applications of Chiral Technology” authored by Kazuo Achinami (published in 1999 by IBC) and “Asymmetric Catalysis in Organic Synthesis” authored by Ryoji Noyori.
Heretofore, compounds capable of causing a substituent such as a phenyl group existing on the phosphorus atom to be nonequivalent by C-chirality or axial asymmetry have been positively studied because they are obtainable by simple synthesis. It has been reported, however, that phosphine compounds having a chiral center directly on the phosphorus atom exert the most outstanding capability to develop asymmetry. Of these ligands, 1,2-bis(o-methoxyphenyl)phenylphosphino)ethane (generally called DIPAMP) is known which is a ligand having been studied in the earliest stage (U.S. Pat. No. 4,008,281 and Japanese Unexamined Patent Application Publication No. 50-113489). Furthermore, a new bisphosphine ligand structured to have a 1,2-bis(phosphino)-ethane group has been proposed by Imamoto et al. (J. Am. Chem. Soc., 1998, 120, pp. 1635-1636 and Japanese Unexamined Patent Application Publication No. 11-80179).
Thus, the 1,2-bis(phosphino)ethane-structured bisphosphine is known to be important as a chiral ligand. For an asymmetric reaction to progress with high reactivity, a substituent-containing aromatic group or a bulky alkyl group needs to be essentially existent on the chiral center, i.e., on the phosphorus atom. The bulky alkyl group known to be possibly attached to the P atom of such a 1,2-bis(phosphine)ethane structure, however, is limited only to a lower alkyl group such as 1,1-diethylpropyl or t-butyl, and a cycloalkyl group such as cyclopentyl, cyclohexyl or 1-adamantyl. Also in the case of other bisphosphine ligands, it is art-recognized that as the bulky alkyl group to be attached to the chiral center, that is, to the phosphorus atom, a chain alkyl group is usually used which has 2 to 4 carbon atoms and is typified by a t-butyl group and that as the alkyl group having a much larger number of carbon atoms, a cycloalkyl group is usually used which is typified by a cyclopentyl or cyclohexyl group. With regard to the chain alkyl group, a bulky alkyl group having 8 or more carbon atoms stands wholly unknown. Therefore, the 1,1,3,3-tetramethylbutyl group-containing bisphosphine compound according to the present invention can be said to be absolutely novel as far as the present inventors know.
The method disclosed in Japanese Unexamined Patent Application Publication No. 11-80179 involves stereoselective deprotonation of (−)-sparteine in an equimolar amount with S-butylithium at a cryogenic temperature of −78° C., thereby obtaining an optically active bisphosphine-borane complex. Such a cryogenic temperature, however, is generally extremely difficult to carry out industrially and hence is far from being practically applicable. In addition, the S-butylithium is a compound that is vigorously active with respect to oxygen and moisture in the air and is difficult to handle on an industrial scale. As a further problem, an optically active form that can be obtained is limited only to a (S, S) form as an absolute configuration, and therefore, this is less advantageous to industrialization.
Optically active bisphosphine ligands have been thus far developed as mentioned above, but they cannot be said to be sufficient in respect of selectivity, catalytic activity and so on. Providing a phosphine ligand not yet known is crucial when the substrates, asymmetry conditions and the like are considered.
To settle the above-noted problems, the present inventors have conducted extensive research, finding that a transition metal complex having a novel 1,1,3,3-tetramethylbutyl group-containing bisphosphine compound as a ligand exhibits a high asymmetric catalytic activity, which group is a bulky substituent having 8 carbon atoms and represented by the foregoing general formula (1), and can also give both (S, S) and (R, R) forms as absolute configurations. This finding has led to completion of the present invention.
Namely, the objects of the invention are to provide a novel bisphosphine compound that is useful as a ligand capable of yielding a higher asymmetric catalytic activity than conventional catalysts, a process for producing the above bisphosphine compound, a transition metal complex having as a ligand the above bisphosphine compound capable of yielding a higher asymmetric catalytic activity than conventional catalysts, and a process for asymmetrically hydrogenating an unsaturated carboxylic acid and its ester using the above transition metal complex as a catalyst.
Disclosure of the Invention
The novel bisphosphine compound intended to be provided by the present invention is a 1,2-bis(methyl(1,1,3,3-tetramethylbutyl)-phosphino)ethane represented by the following general formula (1):
(where t—C
8
H
17
denotes 1,1,3,3-tetramethylbutyl).
Moreover, the process for producing the above-mentioned bisphosphine compound comprises the steps of subjecting a phosphine oxide carboxylate represented by the following general formula (2):
(where A
1
and A
2
denote a methyl group and a 1,1,3,3-tetramethyl-butyl group, respectively, and A
1
and A
2
denote their respective different groups) to Kolbe's electrolytic coupling reaction, thereby obtaining 1,2-bis(methyl(1,1,3,3-tetramethylbutyl)phosphinoyl)-ethane represented by the following general formula (3):
(where A
1
and A
2
have the same meanings as defined above, and A
1
and A
2
denote their respective different groups), and then reducing the resultant 1,2-bis(methyl(1,1,3,3-tetramethylbutyl)phosphinoyl)-ethane with a reducing agent.
Furthermore, the use of the above-mentioned bisphosphine compound is implemented in such a manner that a transition metal complex composed of the bisphosphine compound as a ligand is used as a catalyst to asymmetrically hydrogenate an unsaturated carboxylic acid and its ester.
Best Mode for Carrying Out the Invention
The present invention will now be described in detail.
In the 1,2-bis(methyl(1,1,3,3-tetramethylbutyl)phosphino)-ethane of the invention represented by the foregoing general formula (1), a racemic form and an optically active form are included. As the optically active form, (S, S), (R, R) and meso forms exist, but the invention embraces all such forms.
Next, the process is described for the production of the optically active 1,2-bis(methyl(1,1,3,3-tetramethylbutyl)-phosphino)ethane of the invention represented by the foregoing general formula (1).
The 1,2-bis(methyl(1,1,3,3-tetramethylbutyl)phosphino)-ethane of the invention represented by the foregoing general formula (1) can be easily produced, in essence, by performing a first step in which a phosphine oxide carboxylate represented by the foregoing general formula (2) is subjected to Kolbe's electrolytic coupling reaction, whereby 1,2-bis(methyl-(1,1,3,3-tetramethyl-butyl)phosphinoyl)ethane represented by the foregoing general formula (3) is obtained, and then a first step in which the resultant
Nohira Hiroyuki
Sugiya Masashi
Armstrong Westerman & Hattori, LLP
Nippon Chemical Industries Co., Ltd.
Vollano Jean F.
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