Organometallic catalysts

Details Organometallic catalysts Organometallic catalysts

2000-01-20

2002-08-06

Shaver, Paul F. (Department: 1621)

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

Organic compounds

Silicon containing

C502S103000, C502S117000, C502S225000

Reexamination Certificate

active

06429327

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to catalyst systems and processes of using the same, and more particularly to catalyst systems for making alkyl substituted compounds.
BACKGROUND OF THE INVENTION
In the synthesis of organic compounds, protection groups are used extensively. Protection groups are used to mask specific functionality which then allows other transformations to be effected in the molecule. After the intended transformation is carried out, the protected functionality is then regenerated by removal of the protecting group. The hydroxyl functionality has been found to be effectively protected by transformation to the silyl ether by reaction with alkyl chloro silanes.
Alkyl chloro silanes have been prepared by several methods. One method involves reaction of an alkyllithium with a dialkyl dichloro silane as illustrated below:
The resulting product is the trialkyl chloro silane. Preparation of alkyllithium requires access to lithium industry specific plant equipment and knowledge of handing pyrophric materials on plant scale. See U.S. Pat. No. 5,332,853 to Morrison et al.
Many preparations of alkyl chloro silanes involve chlorination of a trialkyl silane or trialkyl silanol in the last step, as illustrated below:
Unfortunately, preparation of the starting trialkyl silane or trialkyl silanol usually requires several steps and is hence economically unfavorable. See, for example, JP 62022790, JP 60222492, JP 08291180, JP 08119978, EP 652,221, EP 556,802, EP 557,762, JP 06247987, JP 06128274. See also EP 298,487 and U.S. Pat. No. 5,312,949. See also EP 278,368.
Another preparation of alkyl chloro silanes involves reaction of an alkyl magnesium halide with a dialkyl dichloro silane in the present of a catalyst, as illustrated below:
The catalyst of choice to effect reaction is Cu(I)CN. See, for example, JP 0831183, JP 08333374. See also EP 656,363, EP 405,560, and U.S. Pat. No. 4,650,891. Due to the highly toxic nature of Cu(I)CN, industrial preparation of alkyl chloro silanes using an alkyl magnesium process requires experience using toxic materials on industrial scale.
SUMMARY OF THE INVENTION
The present invention provides catalyst systems useful in the production of substituted compounds, including alkyl substituted silane compounds. The catalyst systems of the invention include at least two components. A first component can be a copper (I) or (II) halide, and preferably is copper (I) or (II) chloride. At least one additional metal salt which is different from the copper halide is also present as a catalyst in the mixed catalyst system of the invention. Exemplary metal salts include Group IA, Group IIA, Group IIIA, Group IVA and transition metal salts. The anion of the metal salt can vary, but in one currently advantageous embodiment of the invention, the anion is a cyanide anion.
The mixed catalyst systems of the invention are useful in the production of substituted silanes. In this regard, the present invention also provides a process in which a silane of the formula R
y
H
z
SiX
4−y−z
is reacted with an alkyl magnesium halide of the formula R
1
MgX
1
, wherein each R and R
1
is independently selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl and substituted cycloalkyl, each X is independently selected from the group consisting of halides and alkoxides, X
1
is halide, and y and z can each independently be 0, 1, 2 or 3, in the presence of a mixed catalyst system.
The present invention can provide several advantages. For example, the mixed catalyst systems can be cost effective sources of catalytic activity. Further the present invention can minimize exposure to reagents such as cyanides reagents without detrimental impact on catalytic activity. Further the mixed catalyst system can offer increased flexibility in selection of catalyst reagents.
DETAILED DESCRIPTION OF THE INVENTION
The processes of the invention for making substituted silanes include reacting a silane of the formula R
y
H
z
SiX
4−y−z
with an alkyl magnesium halide of the formula R
1
MgX
1
, wherein each R and R
1
is independently selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl and substituted cycloalkyl, each X is independently selected from the group consisting of halides and alkoxides, X
1
is halide, and y and z can each independently be 0, 1, 2 or 3, in the presence of a mixed catalyst system. In particular, it has been discovered that a mixed catalyst system comprising a copper (I) or (II) halide and a Group IA, IIA, IIIA, IVA, or transition metal salt of an appropriate anion catalyzes the reaction of alkyl magnesium compounds with substituted silanes, including alkyl halo silanes.
A currently preferred copper halide is copper chloride. The metal salt includes salts of Groups IA, IIA, IIIA, and IVA metals of the Periodic Table of Elements, namely, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, Sn, Pb, as well as salts of transition metals such as Fe, Zn, Ti, and Zr, and the like. Exemplary anions useful in the metal salt of the mixed catalyst system of the invention include without limitation Cl
−
, F
−
, R
3
O
−
, R
3
CC
−
, NCS
−
, CN
−
, X
4
O
−
, I
−
, Br
−
, R
3
CO
2
−
, C
2
O
2
−2
, CuCl
4
−
, O
−2
, and R
3−
, wherein each R
3
is independently selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl and substituted aryl and each X is halide.
The reaction can be conducted in a polar or mixed polar/hydrocarbon solvent system, typically at a temperature from about room temperature up to reflux, although reaction temperatures can be outside of this range. Exemplary polar solvents include, but are not limited to, diethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, and the like, and mixtures thereof. Exemplary hydrocarbon solvents include, but are not limited to, inert liquid alkanes, cycloalkanes and aromatic solvents, and mixtures thereof. Exemplary alkanes and cycloalkanes include those containing five to 10 carbon atoms, such as pentane, hexane, cyclohexane, methylcyclohexane, heptane, methylcycloheptane, octane, decane and the like and mixtures thereof. Exemplary aromatic solvents include those containing six to ten carbon atoms, such as toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, n-propylbenzene, isopropylbenzene, n-butylbenzene, and the like and mixtures thereof. A currently preferred solvent is tetrahydrofuran (THF). Each catalyst is present in an amount ranging from about 0.01 to about 15 mole percent, and preferably from about 0.1 to about 1 mole percent.
As used herein, the term “alkyl” refers to straight chain and branched C1-C25 alkyl. The term “substituted alkyl” refers to C1-C25 alkyl substituted with one or more lower C1-C10 alkyl, lower alkoxy, lower alkylthio, or lower dialkylamino. The term “cycloalkyl” refers to C3-C12 cycloalkyl. The term “substituted cycloalkyl” refers to C3-C12 cycloalkyl substituted with one or more lower C1-C10 alkyl, lower alkoxy, lower alkylthio, or lower dialkylamino. The term “aryl” refers to C5-C25 aryl having one or more aromatic rings, each of 5 or 6 carbon atoms. Multiple aryl rings may be fused, as in naphthyl or unfused, as in biphenyl. The term “substituted aryl” refers to C5-C25 aryl substituted with one or more lower C1-C10 alkyl, lower alkoxy, lower alkylthio, or lower dialkylamino. Exemplary aryl and substituted aryl groups include, for example, phenyl, benzyl, and the like.
The current invention has been shown to be particularly useful in the preparation of t-butyl dimethyl silyl chloride, a chloro silane which is commonly used on industrial scale in the pharmaceutical industry. Reaction of t-butyl magnesium chloride with dichlorodimethylsilane resulted in t-butyl dimethyl silyl chloride (TBSCl) preparation in 90% yield using the current invention. This result was obtained employing the mixed catalyst of Cu(I)Cl

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