Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2001-01-05
2001-09-18
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
Reexamination Certificate
active
06291696
ABSTRACT:
This invention relates to a process for preparing 2-[tris(trimethylsilyl)silyl]ethyl methacrylate and 2-[tris(trimethylsilyl)silyl]ethyl acrylate. For brevity sake, methacrylate and acrylate are collectively designated (meth)acrylate.
BACKGROUND OF THE INVENTION
2-[Tris(trimethylsilyl)silyl]ethyl (meth)acrylate is a useful monomer to form a polymer for use in bi-layer photoresist to be processed by lithography using excimer laser light. In the prior art, 2-[tris(trimethylsilyl)silyl]ethyl methacrylate is prepared by an esterification process of reacting a corresponding alcohol, that is, 2-tris(trimethylsilyl)silylethanol with methacryloyl chloride (see Sooriyakumaran et al., SPIE, Vol. 3333, p. 219 and Allen et al., U.S. Pat. No. 5,985,524). The process starting from the acid chloride and the alcohol in these references, however, has the following problems when it is carried out on an industrial scale. The reaction is usually effected using more than an equivalent of a base in a solvent. The acid chloride should be handled with caution since it is corrosived moisture sensitive. Work-up process, including extraction and concentration step, is necessarily required.
On the other hand, 2-[tris(trimethylsilyl)silyl]ethanol is synthesized by reaction of a silicon metal reagent, tris(trimethylsilyl)silyllithium with low-boiling ethylene oxide (boiling point 10.7° C.) (see Brook et al., Organometallics, 1984, 3, p. 1317). This synthesis process also encounters difficulty upon industrial implementation because the awkward-to-handle compound is used.
Also known in the art is the synthesis of 2-[tris(trimethylsilyl)silyl]ethyl acetate by reaction of tris(trimethylsilyl)silane with vinyl acetate (see Kopping et al., J. Org. Chem., 1992, 57, p. 3994). It is also contemplated to synthesize 2-[tris(trimethylsilyl)silyl]ethanol by hydrolyzing or reducing the 2-[tris(trimethylsilyl)silyl]ethyl acetate. Another known example is reduction with lithium aluminum hydride (see Allen et al., U.S. Pat. No. 5,985,524). This process, however, encounters more difficulty because two steps of alcohol formation and esterification reaction are involved.
Another problem is that the intermediate 2-[tris(trimethylsilyl)silyl]ethanol is impossible to purify by distillation since it is a crystal having a melting point of about 150° C. Purification by recrystallization is industrially troublesome, and a substantial loss is inevitable.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved process for preparing 2-[tris(trimethylsilyl)silyl]ethyl methacrylate and 2-[tris(trimethylsilyl)silyl]ethyl acrylate in high yields using 2-[tris(trimethylsilyl)silyl]ethyl acetate as a starting material, the process being easy and safe to carry out on an industrial scale.
It has been found that 2-[tris(trimethylsilyl)silyl]ethyl (meth)acrylate can be prepared simply by reacting 2-[tris(trimethylsilyl)silyl]ethyl acetate with an alcohol in the presence of a catalyst, then reacting the resulting 2-[tris(trimethylsilyl)silyl]ethanol with a (meth)acrylate ester.
The invention provides a process for preparing 2-[tris(trimethylsilyl)silyl]ethyl (meth)acrylate, comprising the steps of reacting 2-[tris(trimethylsilyl)silyl]ethyl acetate with an alcohol in the presence of a catalyst to form 2-[tris(trimethylsilyl)silyl]ethanol, then reacting it with an alkyl (meth)acrylate to form 2-[tris(trimethylsilyl)silyl]ethyl (meth)acrylate.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A first step of the inventive process is to reacting 2-[tris(trimethylsilyl)silyl]ethyl acetate with an alcohol in the presence of a catalyst for ester exchange reaction to form 2-[tris(trimethylsilyl)silyl]ethanol. The alcohol used herein may be selected from among methanol, ethanol, 1-propanol and 1-butanol, though not limited thereto.
The reaction may be effected without a solvent. Solventless reaction is advantageous because extra operations such as concentration and solvent recovery are unnecessary. However, auxiliary use of a solvent is possible. The solvent, if used, is usually selected from hydrocarbons such as hexane, heptane, benzene, toluene, xylene, and cumene; and ethers such as tetrahydrofuran, di-n-butyl ether, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.
The catalyst used herein includes a variety of compounds, for example, acids such as hydrochloric acid, sulfuric acid, trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid; bases such as sodium methoxide, sodium ethoxide, potassium t-butoxide, and N,N-dimethylaminopyridine; salts such as sodium cyanide, potassium cyanide, sodium acetate, potassium acetate, calcium acetate, tin acetate, aluminum acetate, aluminum acetoacetate, and alumina; and Lewis acids such as aluminum trichloride, aluminum ethoxide, aluminum isopropoxide, boron trifluoride, boron trichloride, boron tribromide, tin tetrachloride, tin tetrabromide, dibutyltin dichloride, dibutyltin dibromide, dibutyltin dimethoxide, dibutyltin oxide, titanium tetrachloride, titanium tetrabromide, titanium (IV) methoxide, titanium (IV) ethoxide, titanium (IV) isopropoxide, and titanium (IV) oxide. They may be used alone or in admixture. Of these, Lewis acids such as aluminum trichloride, aluminum ethoxide, aluminum isopropoxide, boron trifluoride, boron trichloride, boron tribromide, tin tetrachloride, tin tetrabromide, dibutyltin dichloride, dibutyltin dibromide, dibutyltin dimethoxide, dibutyltin oxide, titanium tetrachloride, titanium tetrabromide, titanium (IV) methoxide, titanium (IV) ethoxide, titanium (IV) isopropoxide, and titanium (IV) oxide are advantageous since they promote rapid reaction, resulting in higher yields. The catalyst is used in a catalytic amount and usually in an amount of 0.1 to 50 molt based on the moles of the starting reactant, 2-[tris(trimethylsilyl)silyl]ethyl acetate. An amount of 0.1 to 5 mol % is especially desirable from the standpoints of yield and cost.
Reaction is usually effected while heating the reaction system so that the low-boiling alkyl acetate resulting from ester exchange reaction, such as methyl acetate, ethyl acetate, propyl acetate or butyl acetate may be removed from the reaction system.
The resulting product, 2-[tris(trimethylsilyl)silyl]ethanol which can be purified by recrystallization. However, the 2-[tris(trimethylsilyl)silyl]ethanol in the reaction mixture has a sufficient purity for the second step, and can be employed in the next step as the mixture with the catalyst and the solvent (if any), without purification.
The second step of the inventive process is to react the 2-[tris(trimethylsilyl)silyl]ethanol resulting from the first step with a (meth)acrylate ester in the presence of a catalyst for ester exchange reaction to form 2-[tris(trimethylsilyl)silyl]ethyl (meth)acrylate. Examples of the (meth)acrylate ester used herein include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, and n-butyl acrylate. Of these, methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate are preferable because of their cost and rapid progress of reaction.
The reaction may be effected without a solvent. Solventless reaction is advantageous because extra operations such as concentration and solvent recovery are unnecessary. However, auxiliary use of a solvent is possible. The solvent, if used, is usually selected from hydrocarbons such as hexane, heptane, benzene, toluene, xylene, and cumene; and ethers such as tetrahydrofuran, di-n-butyl ether, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether. When the solvent is used in the second step, it is economical that the solvent used in the first step is kept to the second step.
The catalyst used in the
Hasegawa Koji
Kinsho Takeshi
Kiyomori Ayumu
Kubota Tohru
Watanabe Takeru
Millen White Zelano & Branigan PC
Shaver Paul F.
Shin-Etsu Chemical Co. , Ltd.
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