Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-06-07
2002-02-26
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S276000, C564S278000, C564S305000, C564S444000, C564S509000, C568S013000
Reexamination Certificate
active
06350910
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of organic catalytic synthesis. More particularly, it concerns a method for stereospecific isomerisation of allylamines, such as those defined by formula (I) below, using complexes of certain transition metals having, as ligands, chiral phosphorated compounds immobilised by fixation on to a suitable polymer.
PRIOR ART
Isomerisation reactions of prochiral and non-prochiral allylamines, with the aid of complexes of rhodium, iridium or ruthenium have already been known for several years; examples are those represented by the formulae [Rh(P—P)*diene]
+
X
−
, [Rh(P—P)*
2
]
+
X
−
, [Ru(CH
3
COO)
2
(P—P)* ] or [RuY
2
(P—P)*], in which (P—P)* is a phosphorated, bidentate chiral ligand, “diene” represents a diolefin such as cyclo-octadiene or norbornadiene, X
−
is an anion such as a halide, BF
−
4
, PF
−
6
or ClO
−
4
, and Y is a halide. The isomerisation reaction gives rise to the corresponding enamines or imines, which are then hydrolysed to obtain chiral aldehydes, for example citronellal, methoxycitronellal or hydroxycitronellal. These compounds are highly valued materials in perfumery.
These known methods are the subject matter of several publications. Of these one may cite the patents EP-B-068 506, 135 392 and 156 607 (holder: Takasago Perfumery Co.) and JP 61-19203 of the same holder, as well as patent EP-B-398 132 (holder: Hoffmann La Roche AG) and patent application EP 643 065 (applicant: Bayer AG). All the methods described in these reference documents use catalysts having, as the ligand, bidentate chiral phosphines based on biphenyl or binaphthyl systems of symmetry C
2
. The most well-known ligand for this isomerisation reaction, and which is also used in other catalytic methods, is BINAP, represented by the following formula (IV):
One drawback of the use of the catalysts mentioned above resides in the fact that it is difficult to separate the catalyst from the product obtained. The normal method used for obtaining a pure product is distillation of the reaction mixture, obtained by degrading the catalyst, which is then no longer usable.
The chemical literature proposes the fixation on to polymers of ligands known for their use in catalytic reactions, so as to solve the problems of separation of the product from the reaction mixture and of decomposition of the catalyst still present in this mixture. A general account of the existing knowledge in this field may be found in the article of M. Reggelin in Nach. Chem. Tech. Lab. 45(1997), pages 1196-1201.
Application WO 98/12202 of Oxford Asymmetry Limited describes ligands of the BINAP type such as those mentioned above, which are attached to suitable polymers such as, for example, polystyrene, polyamides or aminomethylated polystyrene, by spacer groups comprising, for example, —O—C(O)—, —NH—C(O)—, —O— or —NH— functions linked to alkyl chains. In the examples, this same application also describes the use of these ligands immobilised for the asymmetric hydrogenation of ketones and olefins.
Although the data reveal that these ligands yield roughly the same conversions and enantioselectivities as non-immobilised BINAP, nowhere can a precise indication be found of the nature of the products obtained and of the reaction conditions. Overall, the application reveals that immobilised ligands of the BINAP type, which no longer have the C
2
symmetry of non-immobilised BINAP, can be used in asymmetrical hydrogenations. However, and also due to the fact that not all the necessary information permitting estimation of the true catalytic capacity of these ligands is available, the person skilled in the art is not capable of deducing that ligands of the immobilised BINAP type prove equally effective in asymmetric isomerisation reactions of allylamines.
DESCRIPTION OF THE INVENTION
The aim of the present invention is to find an immobilised ligand which avoids the problems of non-immobilised ligands as stated above, and which is just as effective in respect of conversions and enantioselectivity as the latter in the asymmetric isomerisation of prochiral allylamines.
The aim is achieved by a method for stereospecific isomerisation of prochiral allyl systems represented by the formula
in which R
1
≠R
2
, and each represents an alkyl or alkenyl group, containing 1 to 12 carbon atoms, or an aryl group, possibly substituted by a hydroxy group, R
3
and R
4
representing independently of one another hydrogen, a C
1
to C
12
alkyl or alkenyl group, or an aryl group, R
5
is hydrogen or an alkyl or cycloalkyl group, containing 1 to 8 carbon atoms, R
6
is an alkyl or cycloalkyl group, containing 1 to 8 carbon atoms, or R
5
and R
6
are taken together with the nitrogen to form a ring having 5 or 6 atoms, or a ring having 6 atoms and containing oxygen, into enamines represented by the formula
in which the symbols R
1
-R
6
have the meanings assigned above, or into imines represented by the formula
in which the symbols R
1
-R
4
and R
6
have the meanings assigned above and R
5
is hydrogen, by means of catalysts of Rh, Ir or Ru having at least one chiral phosphorated ligand, the method being characterised in that the phosphorated ligand in the catalyst of Rh, Ir or Ru is a ligand represented by the formula
in which Ar represents a phenyl or tolyl group,
R
1
is a unit of the type Z—B—, in which
B is a group linking the polymer Z with the ligand, selected from among the groups —O—C(O)—(CH
2
)
n
—, —NH—C(O)—(CH
2
)
n
—, —O—(CH
2
)
n
—, —NH—(CH
2
)
n
— and —(CH
2
)
n
—, n being a whole number from 1 to 10, and
Z is a polymer or copolymer selected from among silica, polystyrene, the polyamides, TENTAGEL resins (grafted copolymers having a low crosslinked polystyrene matrix on which polyethyleneglycol or polyoxyethylene is grafted), the functionalised polystyrene of the Merrifield resin type, aminomethylated polystyrene, or [4-(hydroxymethyl)phenoxymethyl] polystyrene (“Wang resin”); or in which the phosphorated ligand is a ligand represented by formula
in which Ar is a phenyl or tolyl group, R
2
≠R
3
and
R
2
and R
3
represent hydrogen or a unit of the type Z—B′—,
B′ being a group linking the polymer Z and the ligand, selected from among the groups —C(O)—, —(CH
2
)
m
— or —NH—C(O)—(CH
2
)
m
—C(O)—, m being a whole number from 1 to 4, and
Z being a polymer as defined above, R
2
=R
3
=H being excluded.
We found that the ligands according to formulae (V) and (VI) are very useful for preparing metallic catalysts which are active in the stereospecific isomerisation of allylamines into amines or chiral imines. More particularly, they proved to be highly effective in the isomerisation of diethyl geranylamine and of diethyl nerylamine. We were able to verify that the immobilisation of the ligands used in the present invention has no negative effect on their performance, and even enables advantageous and unanticipated results to be obtained by comparison with non-immobilised ligands.
The polymers or copolymers which may be used as carriers for the ligands in the context of the present invention are the state-of-art ones and include silica, polyamides and polystyrene, particularly functionalised and, as the case may be, cross-linked polystyrenes. Non-limiting examples of this type of polymer are functionalised polystyrenes cross-linked to divinyl benzenes (called Merrifield resins), TENTAGEL resins (grafted copolymers having a low crosslinked polystyrene matrix on which polyethyleneglycol or polyoxyethylene is grafted), functionalised polystyrene of the Wang resin type, or [4-(hydroxymethyl)phenoxymethyl] polystyrene, and aminomethylated polystyrene.
The preferred ligands of formula (V) are those in which R
1
is a unit of the type —(CH
2
)
3
—C(O)O—CH
2
—Z, Z being the resin of the “Wang” type, or a unit of the type —(CH
2
)
3
—C(O)NH—CH
2
—Z, Z being polystyrene.
Regarding formula (VI) ligands, those in which R
2
is a unit of the type —(CH
2
)
2
—(O—C
2
H
Davis Brian J.
Firmenich SA
Padmanabhan Sreeni
Winston & Strawn
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