Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2002-11-18
2004-08-03
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06770777
ABSTRACT:
TECHNICAL FIELD
This invention relates to a process for preparing an 2-alkyl-2-adamantyl ester such as 2-alkyl-2-adamantyl acrylates and 2-alkyl-2-adamantyl methacrylates (hereinafter, collectively referred to as 2-alkyl-2-adamantyl (meth)acrylates), which are useful as a material for producing a semiconductor resist.
BACKGROUND OF THE INVENTION
A resist prepared from an 2-alkyl-2-adamantyl ester as a starting material has been known to be highly resistant to dry etching during a process for producing a semiconductor (see, e.g., JP-A 5-265212), and has been thus expected to be a promising resist for a semiconductor.
A known process for preparing an 2-alkyl-2-adamantyl ester involves alkylating 2-adamantanone using an alkylating agent consisting of an organometallic compound, and then esterifying the resulting metal 2-alkyl-2-adamantyl alcoholate with an acid halide (e.g., JP-A 10-182552).
In the first alkylation step in the above reaction, when the alkylating reagent is an organomagnesium or organoaluminum compound, a reduction reaction preferentially proceeds, leading to a reduced yield of the alkyl compound as described in, e.g., Tetrahedron Lett., Vol. 31 (22), p. 3151 (1990). Thus, a desired ester may be obtained in a significantly lower yield.
For example, as described in Comparative Examples later, selectivities for an alkylated product (an ethylated compound) and a reduced product (2-adamantanol) were 25% and 75%, respectively, in a reaction of 2-adamantanone with ethylmagnesium iodide. As a result, a reaction yield of the ester was significantly low, i.e., about 20% based on 2-adamantanone. In the reaction, a lower content of the ester makes its purification very difficult. Thus, the ester with a high purity cannot be obtained using a common purification method.
In general, alkylation using an alkyllithium as an alkylating reagent may frequently eliminate a reduction reaction as described above, allowing the above problem to be solved. An alkyllithium itself may be, however, prepared in a lower yield and has a short half life as indicated in J. Am. Chem. Soc., Vol. 63, p. 2480 (1941) describing that ethyl lithium is prepared from ethyl bromide and lithium metal in an yield of at most about 50%, and in “Yuki Kagaku Jikken No Tebiki (Guide for Organic Chemical Experiments), Kagaku Dojin, p. 34 (1988) describing that ethyl lithium has a half life as short as 54 hours. Thus, the reagent is expensive and unstable.
Alkylation with an alkyllithium is, therefore, not unfavorable due to its higher production cost and troublesome operation in the light of the overall production process. Thus, the yield in the first alkylation step also significantly affects the yield of the ester.
On the other hand, there have been known the conditions under which the second esterification step may stoichiometrically proceed, particularly when the metal is lithium. However, when using acryloyl chloride or methacryloyl chloride (hereinafter, acrylic and methacrylic acids are collectively referred to as (meth)acrylic acid) as an acid halide for esterification of a metal 2-alkyl-2-adamantyl alcoholate prepared by alkylation of 2-adamantanone, an ester produced is polymerized during the reaction, resulting in a reduced overall yield.
A resist material for a semiconductor must be highly pure. Conventional processes for preparing an 2-alkyl-2-adamantyl ester, therefore, carry industrially serious problems in terms of a lower yield and difficulty in purification.
SUMMARY OF THE INVENTION
We have extensively investigated processes for preparing an 2-alkyl-2-adamantyl (meth)acrylate by reacting lithium 2-alkyl-2-adamantyl alcoholate with (meth)acryloyl chloride, and have found that an —OLi group in an lithium 2-alkyl-2-adamantyl alcoholate polymerizes 2-alkyl-2-adamantyl (meth)acrylate produced by the reaction.
In addition, we have found that when a solution of lithium 2-alkyl-2-adamantyl alcoholate is added to (meth)acryloyl chloride, polymerization of the 2-alkyl-2-adamantyl(meth)acrylate can be prevented.
Furthermore, we have intensely investigated alkylation of 2-adamantanone and have found that 2-adamantanone can be alkylated by reacting 2-adamantanone, lithium metal and an alkyl halide instead of using an unstable alkyllithium described above. We have also found that a solution containing 2-adamantanone and alkyl halide can be slowly added to lithium metal to alkylate 2-adamantanone more effectively, and that the alkylation reaction gives a highly pure product and thus a resulting solution can be directly used in the subsequent esterification without further isolation to give a highly pure product after isolation. Thus, this invention has been achieved on the basis of these findings.
Thus, an objective of this invention is to provide a process for preparing an 2-alkyl-2-adamantyl ester with a high purity in an improved yield from 2-adamantanone without using an expensive and unstable compound such as an alkyl lithium.
Another objective of this invention is to provide a process for preparing an 2-alkyl-2-adamantyl ester whereby the ester can be produced in a high yield by preventing the ester from polymerizing during esterification of a metal 2-alkyl-2-adamantyl alcoholate with an acid halide.
For realizing the above objectives, this invention provides:
[1] A process for preparing an 2-alkyl-2-adamantyl (meth)acrylate comprising the step of adding a solution of a lithium 2-alkyl-2-adamantyl alcoholate to a (meth)acryloyl halide to react the lithium 2-alkyl-2-adamantyl alcoholate with the (meth)acryloyl halide.
[2] The process for preparing an 2-alkyl-2-adamantyl (meth)acrylate as described in [1] wherein the solution of the lithium 2-alkyl-2-adamantyl alcoholate is prepared by combining a solution or suspension containing 2-adamantanone and an alkyl halide with lithium metal.
[3] The process for preparing an 2-alkyl-2-adamantyl (meth)acrylate as described in [1] wherein the alkyl is alkyl having 1 to 6 carbon atoms.
[4] The process for preparing an 2-alkyl-2-adamantyl (meth)acrylate as described in [1] wherein the alkyl is ethyl.
In this invention, a solution or suspension of 2-adamantanone and an alkyl halide is reacted with lithium metal to prepare a solution of an lithium 2-alkyl-2-adamantyl alcoholate. The lithium 2-alkyl-2-adamantyl alcoholate can be, therefore, prepared in a high yield and furthermore, the resulting alcoholate is reacted with an acid halide to give a desired product, an 2-alkyl-2-adamantyl ester in a high yield.
The lithium 2-alkyl-2-adamantyl alcoholate can be prepared in a high yield when a solution or suspension of 2-adamantanone and an alkyl halide is added to lithium metal. Furthermore, when the solution of the lithium 2-alkyl-2-adamantyl alcoholate thus prepared is added to an esterifying agent or its solution, the desired product, 2-alkyl-2-adamantyl (meth)acrylate, is prevented from polymerizing. As a result, the yield of the desired product is improved. Furthermore, a reduced amount of impurities in the desired product makes a purification process easier and thus the desired product can be obtained easier with a high purity.
According to the preparation process of this invention, a desired product can be obtained in a higher yield than a process using a Grignard reagent. In addition, since the process does not use an alkyllithium which must be separately prepared and is unstable, an adamantyl ester can be easily prepared with a lower cost.
BEST MODE FOR CARRYING OUT THE INVENTION
Preparation of a Lithium 2-alkyl-2-adamantyl Alcoholate
As described above, in the first step of the process according to this invention, a solution or suspension of 2-adamantanone represented by formula (1) and an alkyl halide represented by formula (2):
R
1
-X (2)
wherein R represents alkyl having 1 to 6 carbon atoms and X represents halogen, is combined with lithium metal for initiating alkylation of 2-adamantanone to prepare a lithium 2-alkyl-2-adamantyl alcoholate represented by formula (3):
wherein
Hirota Yoshihiro
Kikuchi Hideki
Yamaguchi Masao
Richter Johann
Tokuyama Corporation
Zucker Paul A.
LandOfFree
Process for producing 2-alkyl-2-adamantyl ester does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing 2-alkyl-2-adamantyl ester, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing 2-alkyl-2-adamantyl ester will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3360154