Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1999-07-22
2001-11-06
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S104000
Reexamination Certificate
active
06313340
ABSTRACT:
BACKGROUND OF THE INVENTION
Methyl p-vinylbenzoate has been prepared from a number of different synthetic pathways over the years including the most direct route, esterification of p-vinylbenzoic acid itself. However, even with the direct esterification route itself, one must first prepare the p-vinylbenzoic acid which can involve a number of synthetic sequences in itself. Thus, a number of approaches have been developed which produce methyl p-vinylbenzoate without going through the acid first.
The most direct olefination route prior to this invention involved reacting methyl p-formylbenzoate under boron-Wittig like conditions as is described by Saki, et al in Tetrahedron, 52(3), 915, 1996. However, the use of Knochel's borylmethylcopper reagent does not lend itself for large-scale industrial reactions nor is it economical for producing such quantities.
Several olefination routes based on Heck and Heck-related arylation of ethylene have been reported. One such method involving the palladium catalyzed arylation of ethylene with methyl p-bromobenzoate has been described by J. Kiji, et al in J. Mol. Cat. A:
Chem.
97, 73, 1995. A reaction involving methyl p-iodobenzoate has been described by Rule and Fugate in U.S. Pat. No. 4,935,559 (assigned to Eastman Kodak). Both of the latter reactions involve the use of halogenated compounds which one must address environmental concerns. Other related chemistries involve methyl p-chlorosulfonylbenzoate as described by Kasahara, et al in Chem. Ind., 6, 192, 1989 and arenediazonium salts as described by Kikukawa, et al in Bull. Chem. Soc. Jpn., 52(9), 2609, 1979.
Still, other routes involve the oxidation of methyl p-ethylbenzoate to either methyl p-acetylbenzoate first as in British patent 636,196 (assigned to Monsanto Chemical Company) and by Emerson, et al in J. Am. Chem. Soc., 68, 674, 1946 or to the methyl p-alpha-hydroxyethylbenzoate via the bromo-derivative as described by Bergmann and Blum in J. Org. Chem., 24, 549, 1959. Although these routes could produce large-quantities of methyl p-vinylbenzoate, they too have several synthetic steps not mentioned which adds to the cost of production.
Methyl p-vinylbenzoate has been prepared by several groups of individuals which is more suited to academic and smaller research laboratories. These processes include p-methylacetophenone described by Bergmann and Blum, or through either p-cyanoacetophenone or p-dibromobenzene, both described by Marvel and Overberger in J. Am. Chem. Soc., 67, 2250,1945.
The process of direct olefination of an aromatic aldehyde with ketene in the presence of a potassium salt has been described previously by Hurd and Thomas in J. Am. Chem. Soc., 55, 275, 1933 and by Vittum in his PhD Thesis, Cornell University, 1933. The most detailed work describing this olefination which in many ways resembles the Perkin reaction has been described by Vittum. Most reactions were carried out using benzaldehyde with ketene and some type of “catalyst” to prepare styrene and cinnamic acid, the primary reaction products from this reaction. It has been found that temperature variations over a relatively wide range have little impact on the yields and ratios of styrene and cinnamic acid. Additionally, a salt is needed in the course of the reaction and in particular, potassium salts are preferred.
Prior studies involving substituted aromatic aldehydes such as meta-and para-nitrobenzaldehyde, and anisaldehyde (para-methoxybenzaldehyde) suggest that direct olefination of the aldehyde group with ketene is not very feasible. In these cases, no reaction products of meta- or para-nitrovinylbenzene (meta-or para-nitrostyrene) or para-methoxyvinyl-benzene (para-methoxystyrene) was produced and only in the case of meta-nitrobenzaldehyde were any of the corresponding cinnamic acid derivatives isolated. In particular, the starting aldehyde is generally recovered or a tarry residue formed in addition to the recovered starting aldehyde. Most substituted aldehydes in the Perkin reaction, especially those substituted in the para position have a large negative influence on the rate of reaction. Additionally, the type of substituent can have a large influence on the reactivity of the aldehyde in the Perkin reaction.
Thus, the need exists for a process for preparation of methyl p-vinylbenzoate from the reaction of methyl p-formylbenzoate with a ketene in the presence of a potassium salt. The present invention provides such a process.
BRIEF SUMMARY OF THE INVENTION
The present invention describes a direct method for preparation of methyl p-vinylbenzoate by the reaction of methyl p-formylbenzoate with ketene in the presence of a potassium salt. The present method has the advantage of large-scale economical production of methyl p-vinylbenzoate. It is both unexpected and unobvious that methyl p-formylbenzoate with its para methyl ester substituent would even react with ketene in the presence of a potassium salt to form methyl p-vinylbenzoate, based on prior work by others as discussed above.
The above reaction also yields p-carbomethoxycinnamic acid as a coproduct with methyl p-vinylbenzoate. It has also been discovered that additional quantities of methyl p-vinylbenzoate may be prepared by thermal decarboxylation of p-carbomethoxycinnamic acid in the presence of copper powder. Methyl p-vinylbenzoate may be further reacted by hydrolysis to form p-vinyl benzoic acid.
Both methyl p-vinylbenzoate and p-vinyl benzoic acid have been found to be useful monomers for emulsion polymerization with other ethylenically unsaturated monomers to form latex compositions. Both the latex compositions and the monomers of the present invention may be used in a number of end-use applications, such as coatings, photoresists, and as a partial replacement of styrene in unsaturated polyesters.
DETAILED DESCRIPTION OF THE INVENTION
Applicants have discovered processes for the preparation of methyl p-vinylbenzoate (MVB) from methyl p-formylbenzoate. More specifically, methyl p-formylbenzoate reacts with ketene in the presence of a potassium salt, such as potassium acetate, to form methyl p-vinylbenzoate and p-carbomethoxycinnamic acid.
The source of ketene generation used may be from the pyrolysis of acetone; however, any other method of ketene generation known in the art may be used. Ketene may also be obtained by pyrolysis of, for example, diketene, acetic anhydride, and acetic acid. The relative amount of ketene to methyl p-formylbenzoate used may vary from less than 10 percent to more than 500 percent depending on conditions used, desired conversion rates, and desired selectivity.
Suitable potassium salts for initiation of the reaction include, but are not limited to potassium acetate, potassium carbonate, potassium benzoate, potassium cinnamate, and potassium proprionate. When an equivalent of potassium salt is used, based on the aldehyde, almost no styrene is produced; while 15-20 percent of p-carbomethoxycinnamic acid is produced.
The level of potassium salt used may vary from less than one mole percent to more than 100 mole percent based on methyl p-formylbenzoate. It is preferred that the molar ratio of potassium salt to methyl p-formylbenzoate be less that 0.50. It is even more preferred that the molar ratio of potassium salt to methyl p-formylbenzoate be less than 0.20.
At low temperatures, it may be necessary to dissolve the methyl p-formylbenzoate in a suitable solvent. Useful solvents for the reaction include aliphatic and cycloaliphatic hydrocarbons; aromatic hydrocarbons; cyclic and acyclic ethers, esters and ketones. The amount of solven may be as much as necessary to make up to a 0.001 molar solution. Preferably, the methyl p-formylbenzoate is dissolved in enough solven to make a 0.1 to 10.0 molar solution. At higher temperatures, solvents may not be necessary to carry out the reaction.
In general terms, the process of the present invention involves reacting a mixture of an aromatic aldehyde and potassium salt with ketene. More specifically, the aromatic aldehyde is methyl p-formylbenzoate. The mixture of aromatic al
Elliott Matthew Lynn
Heidt Philip Conrad
Sharma Mahendra Kumar
Eastman Chemical Corporation
Geist Gary
Gwinnell Harry J.
Reyes Hector M
Smith, Esq. Matthew
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