Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1998-08-27
2001-04-03
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S155000, C502S156000, C502S162000, C502S167000, C526S090000, C526S161000, C526S172000
Reexamination Certificate
active
06211107
ABSTRACT:
This invention relates to a novel process for preparing epoxides from olefins and in particular chirally enriched epoxides, certain novel catalysts used in such process and compounds associated with process.
WO 91/14694 described certain catalysts of the following formula (I):
in which
M is a transition metal ion, A, is an anion, and n is either 0, 1 or 2. At least one of X
1
or X
2
is selected from the group consisting of silyls, aryls, secondary alkyls and tertiary alkyls; and at least one of X
3
or X
4
is selected from the same group. Y
1
, Y
2
, Y
3
, Y
4
, Y
5
and Y
6
are independently selected from the group consisting of hydrogen, halides, alkyls, aryl groups, silyl groups, and alkyl groups bearing heteroatoms such as alkoxy and halide, Also, at least one of R
1
, R
2
, R
3
and R
4
is selected from a first group consisting of H, CH
3
, C
2
H
5
and primary alkyls. Furthermore, if R
1
is selected from said first group, then R
2
and R
3
are selected from a second group consisting of aryl groups, heteroatom-bearing aromatic groups, secondary alkyls and tertiary alkyls. If R
2
is selected from said first group, then R
1
and R
4
are selected from said second group. If R
3
is selected from said first group, and R
1
and R
4
are selected from said second group. If R
4
is selected from said first group, then R
2
and R
3
are selected from said second group. Such catalysts are described as being useful in enantioselectively epoxidising a prochiral olefin.
In addition WO 91/14694 described certain catalysts of the formula shown below, herein referred to as formula (IA):
where M is defined as a transition metal ion and A is an anion; where n is either, 3,4,5 or 6; where at least one of X
1
or X
2
is selected from the group consisting of aryls, primary alkyls, secondary alkyls, tertiary alkyls, and hetero atoms; where at least one of X
3
or X
4
is selected from the group consisting of aryls, primary alkyls, secondary alkyls, tertiary alkyls, and hetero atoms; where at least one of Y
1
or Y
2
is selected from the group consisting of aryls, primary alkyls, secondary alkyls, tertiary alkyls, and hetero atoms; where at least one of Y
4
or Y
5
is selected from the group consisting of aryls, primary alkyls, secondary alkyls, tertiary alkyls, and hetero atoms; where Y
3
and Y
6
are independently selected from the group consisting of hydrogen and primary alkyl groups; where R
1
and R
4
are trans to each other and at least one of R
1
and R
4
is selected from the group consisting of primary alkyls and hydrogen; and where the carbons in the (C)
n
portion have substituents selected for the group consisting of hydrogen, alkyl, aryl, and heteratoms.
Such catalysts are described as being useful in enantioselectively epoxidising a prochiral olefin. These catalysts belong to the class of catalysts known in the art as ‘salen catalysts.’
Co-pending International Patent Application Number PCT/GB93/01666 (now International Patent Application, Publication Number WO 94/03271) also discloses a series of salen catalysts, structurally distinct from the catalysts for formula (I) and having the general formula (II):
in which M is a transition metal ion:
A is a counter-ion if required;
r, s and t are independently 0 to 3 such that r+s+t is in the range of 1 to 3;
R
a
, R
b
, R
c
are each independently hydrogen or CH
2
OR′ where R′ is hydrogen or an organic group;
B and E are independently oxygen, CH
2
, NR
d
in which R
d
is alkyl, hydrogen, alkylcarbonyl, or alkylcarbonyl or SO
n
where n is 0 or an integer 1 or 2, with the proviso that B and E are not simultaneously CH
2
and that when B is oxygen, NR
d
or SO
n
, then r cannot be 0, and when E is oxygen, NR
d
or SO
n
, then t cannot be 0;
R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
and R
10
are independently hydrogen, alkyl or alkoxy.
The compounds of formula (II) also catalyse the enantioselective expoxidiation of certain prochiral olefins.
It has been suggested in the art that the use of compounds such as pyridine oxide and 2-methyl imidazole in combination with certain chiral (salen) manganese (III) complex catalysts improves the chemical yield such reactions (Syn. Lett. April 1991, 265-266), although the effect upon the enantioselectivity of the catalysed reactions is currently not clear (Tetrahedron Vol. 50, No 15 p. 4323-4334, 1994). In this context pyridine oxide and 2-methyl imidazole are referred to as ‘donor ligands’ as they are considered to donor-bond to the metallic ion of the salen catalyst.
One particular problem associated with the use of such donor ligands is the complete removal of the donor ligand from the final epoxide product, especially in large scale reactions and most especially when two phase reaction systems are used.
It has now been discovered that one particular compound, isoquinoline N-oxide, previously unreported as a donor ligand, is particularly efficient as a donor ligand in that it advantageously enhances catalyst turnover and in addition it possesses very good solubility characteristics for use as a donor ligand, enabling it to be used in the metal salen complex catalysed epoxidation reactions and subsequently to be readily removed from the epoxide products of the reaction. It has also been discovered that a particular group of salen catalysts are especially suited to use with donor ligands in that the presence of the donor ligands consistently produces not only an increase in reaction rate but also an increase in the enantioselective specificity of the epoxidation reactions.
In addition a further series of salen catalysts which are structurally distinct from those of formulae, (I), (IA) and (II) has now been prepared which surprisingly are also able to catalyse the enantioselective expoxidiation of certain prochiral olefins.
Accordingly, in a first aspect, the invention provides a process for enantioselectively epoxidising a prochiral olefin, which process comprises reacting the prochiral olefin with a source of oxygen in the presence of a salen catalyst and a source of an electron donating ligand, characterised in that the donor ligand is isoquinoline N-oxide or a compound having donor ligand activity and having substantially the same solubility characteristics as isoquinoline N-oxide.
A suitable salen catalyst is a compound of formula (I), (IA), (II) or a compound of formula (III) (which compound of formula (III) is defined hereinafter).
The invention also provides isoquinoline N-oxide or a compound having donor ligand activity and having substantially the same solubility characteristics as isoquinoline N-oxide, for use as a donor ligand.
In a further aspect the invention provides a process for enantioselectively epoxidising a prochiral olefin, which process comprises reacting the prochiral olefin with a source of oxygen in the presence of a salen catalyst and a source of an electron donating ligand, characterised in that the salen catalyst is a compound of formula (II).
A source of an electron donating ligand is suitably provided by a compound which is capable of forming a donor bond with the transition metal M of the said salen catalyst, such that in use the rate of the epoxidation reaction is increased and the enantioselective specificity of the resulting product may also be increased.
A source of electron donating ligand is suitably provided by a compound which is capable of forming a donor bond with the transition metal M of the salen catalyst such that in use the enantioselective specificity of the compound of formula (I) is increased.
A suitable source of an electron donating ligand may be selected from the list consisting of pyridine N-oxide, 2-methyl pyridine N-oxide, 4-methyl pyridine N-oxide, 4-phenyl pyridine N-oxide or isoquinoline N-oxide, especially isoquinoline N-oxide.
In the compounds of formula (I) and (IA);
Preferred values for M, A, n, X
1
, X
2
, X
3
, X
4
, Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, Y
6
, R
1
, R
2
, R
3
and R
4
are as defined in WO 91/14694.
Suitable catalysts are those of formula (IA) as defined above.
A preferred sub-g
Attrill Robin Patrick
Bell David
Finney Frances
Miller David
Turner Gillian
Bell Mark L.
DiVerdi Michael J.
Kinzig Charles M.
McCarthy Mary E.
SmithKline Beecham p.l.c.
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