Phosphinite-oxazolines and metal complexes thereof

Details Phosphinite-oxazolines and metal complexes thereof Phosphinite-oxazolines and metal complexes thereof

2001-09-20

2002-12-24

Higel, Floyd D. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C548S239000, C548S119000

Reexamination Certificate

active

06498256

ABSTRACT:

The present invention relates to chiral phosphinitemothyl-oxazolines; to a process for the preparation thereof; to intermediates used in the preparation thereof; to metal complexes with metals selected from sub-groups I and VII of the Periodic Table of the Elements (d-10 and d-8 metals, referred to as TM8 metals hereinbelow) and phosphinitomethyl-oxazolines as ligands; to a process for asymmetric synthesis by means of an addition reaction between hydrogen, borohydrides or silanes and a carbon-carbon or carbon-hetero atom multiple bond in prochiral organic compounds or by means of an addition reaction between C-nucleophiles or amines and allylic compounds, especially for asymmetric hydrogenation of carbon-carbon or carbon-hetero atom multiple bonds with hydrogen, in the presence of catalytic amounts of the metal complexes; and to the use of the metal complexes as catalysts for asymmetric synthesis by means of an addition reaction between hydrogen, borohydrides or silanes and a carbon-carbon or carbon-hetero atom multiple bond in prochiral organic compounds or by means of an addition reaction between C-nucleophiles or amines and allylic compounds, especially for asymmetric hydrogenation of carbon-carbon or carbon-hetero atom multiple bonds with hydrogen.
G. Helmchen and A. Pfaltz in Accounts of Chemical Research, Volume 33, Number 6, pages 336 to 345 (2000) describe chiral phosphinophenyl-oxazolines as P,N ligands for asymmetric catalysts that are used inter alia in the enantioselective addition of nucleophiles to carbon-carbon double bonds. The oxazoline ring is substituted with bulky groups in the &agr;-position to the nitrogen atom to form an asymmetric centre (carbon atom).
It has been found, surprisingly, that it is possible to prepare in simple manner P,N ligands that contain a phosphinitemethyl group in the &agr;-position to the nitrogen atom to form an asymmetric centre (carbon atom), which phosphinitemethyl group serves at the same time as a chelating group. Those substituted oxazolines form with TM8 metals chiral complexes that are excellent catalysts for the enantioselective addition of hydrogen, borohydrides or silanes to a carbon-carbon or carbon-hetero atom multiple bond in prochiral organic compounds or of C-nucleophiles or amines to allylic compounds or for the enantioselective coupling of aryl or alkenyl triflates to olefins (Heck reaction). Especially in the enantio-selective hydrogenation of prochiral olefins catalysed with Ir complexes, particularly high optical yields are observed. In addition, the phosphinite groups in the ligands exhibit a surprisingly high stability towards hydrolysis. The starting materials for the preparation of the ligands are simple, in some cases commercially available organic molecules that can be combined with one another in a variety of ways, so that the steric and electronic properties of the ligands in respect of catalytic activity and steric selectivity can be adapted to the substrates to be reacted in an outstanding manner.
The invention relates to compounds of formulae I and Ia,
wherein
X
1
is secondary phosphino;
R
3
is hydrogen, a hydrocarbon radical having from 1 to 20 carbon atoms, a heterohydro-carbon radical, bonded via a carbon atom, having from 2 to 20 atoms and at least one hetero atom selected from the group OS and NR, or ferrocenyl;
R is H or C
1
-C
4
alkyl;
each R
4
individually or both R
4
together are a hydrocarbon radical having from 1 to 20 carbon atoms; and
R
01
and R
02
are each independently of the other a hydrogen atom or a hydrocarbon radical having from 1 to 20 carbon atoms.
The phosphine group X
1
may contain two identical or two different hydrocarbon radicals or the two hydrocarbon radicals may form with the P atom a 3- to 8-membered ring. Preferably the phosphine group contains two identical hydrocarbon radicals. The hydrocarbon radicals may be unsubstituted or substituted and they may contain from 1 to 22, preferably from 1 to 12, carbon atoms. Of the compounds of formulae I and la special preference is given to those wherein the phosphine group contains two identical or different radicals selected from the group: linear or branched C
1
-C
12
alkyl; C
5
-C
12
cycloalkyl or C
5
-C
12
cycloalkyl-CH
2
— unsubstituted or substituted by C
1
-C
6
alkyl or by C
1
-C
6
alkoxy; phenyl or benzyl; and phenyl or benzyl substituted by halogen (for example F, Cl and Br), C
1
-C
6
alkyl, C
1
-C
6
haloalkyl (for example trifluoromethyl), C
1
-C
6
alkoxy, C
1
-C
6
haloalkoxy (for example trifluoromethoxy), (C
6
H
5
)
3
Si, (C
1
-C
12
alkyl)
3
Si, secondary amino or by —CO
2
—C
1
-C
6
alkyl (for example —CO
2
CH
3
).
The two radicals in the phosphine group may together also be dimethylene, trimethylene, tetramethylene or pentamethylene unsubstituted or substituted by halogen, C
1
-C
6
alkyl or by C
1
-C
6
alkoxy. The substituents are preferably bonded in the two ortho positions to the P atom.
The phosphine groups may also be those of formulae
wherein o and p are each independently of the other an integer from 2 to 10, and the sum of o+p is from 4 to 12, preferably from 5 to 8, and the phenyl rings are unsubstituted or substituted by C
1
-C
4
alkyl and C
1
-C
4
alkoxy. Examples are [3.3.1]- and [4.2.1]-phobyl of the formulae
Examples of secondary phosphine groups in which the two hydrocarbon radicals form with the P atom a 3- to 8-membered ring are especially those of the formula
which may be substituted in one or both ortho positions and optionally the meta positions to the P atom by C
1
-C
4
alkyl and/or by C
1
-C
4
alkoxy.
Examples of P substituents as alkyl, which preferably contains from 1 to 6 carbon atoms, are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and the isomers of pentyl and hexyl. Examples of P substituents as unsubstituted or alkyl-substituted cycloalkyl are cyclopentyl, cyclohexyl, methyl- and ethyl-cyclohexyl and dimethylcyclohexyl. Examples of P substituents as phenyl and benzyl substituted by alkyl, alkoxy, haloalkyl and/or by haloalkoxy are methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, methylbenzyl, methoxyphenyl, dimethoxyphenyl, trifluoromethylphenyl, bis-trifluoromethylphenyl, tris-trifluoromethylphenyl, trifluoromethoxyphenyl and bis-trifluoromethoxyphenyl.
Preferred phosphine groups X
1
are those which contain identical or different, preferably identical, radicals selected from the group C
1
-C
6
alkyl; cyclopentyl or cyclohexyl unsubstituted or substituted by from 1 to 3 C
1
-C
4
alkyl or C
1
-C
4
alkoxy substituents; benzyl and especially phenyl, which are unsubstituted or substituted by from 1 to 3 C
1
-C
4
alkyl, C
1
-C
4
alkoxy, F, Cl, C
1
-C
4
fluoroalkyl or C
1
-C
4
fluoroalkoxy substituents.
In the compounds of formula I, X
1
is preferably the group —PR
1
R
2
wherein R
1
and R
2
are each independently of the other a hydrocarbon radical having from 1 to 20 carbon atoms, which is unsubstituted or substituted by halogen, C
1
-C
6
alkyl, C
1
-C
6
haloalkyl, C
1
-C
6
alkoxy, C
1
-C
6
haloalkoxy, (C
6
H
5
)
3
Si, (C
1
-C
12
alkyl)
3
Si or by —CO
2
—C
1
-C
6
alkyl; or wherein R
1
and R
2
together are dimethylene, trimethylene, tetramethylene or pentamethylene unsubstituted or substituted by C
1
-C
4
alkyl and/or by C
1
-C
4
alkoxy.
R
1
and R
2
are preferably identical or different, especially identical, radicals selected from the group: branched C
3
-C
6
alkyl; cyclopentyl or cyclohexyl unsubstituted or substituted by from one to three C
1
-C
4
alkyl or C
1
-C
4
alkoxy substituents; benzyl unsubstituted or substituted by from one to three C
1
-C
4
alkyl or C
1
-C
4
alkoxy substituents, and especially phenyl unsubstituted or substituted by from one to three C
1
-C
4
alkyl, C
1
-C
4
alkoxy, —NH
2
, OH, F, Cl, C
1
-C
4
fluoroalkyl or C
1
-C
4
fluoroalkoxy substituents.
R
1
and R
2
are more especially identical or different, especially identical, radicals selected from the group: phenyl unsubstituted or substituted by from one to three C
1
-C
4
alkyl, C
1
-C
4
alkoxy or C
1
-C
4
fluoroalkyl substituents.
The rad

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