Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-07-24
2002-08-27
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S484000, C568S449000, C568S426000
Reexamination Certificate
active
06441246
ABSTRACT:
This is a US National Stage Application of PCT/JP99/04633 filed Aug. 27, 1999 now WO 00/12457 published Nov. 9, 2000.
FIELD OF THE INVENTION
This invention provides a method for simple and highly efficient preparation of aldehydes in which organic carboxylic acids are reduced to corresponding organic aldehydes with molecular hydrogen in the presence of catalysts, wherein said reaction is performed in the presence of a dehydrating agent.
BACKGROUND ART
Aldehydes are used, not only for perfume, drugs and agricultural chemicals by themselves but also as raw materials for synthesis of fine chemicals. As the conventional procedures of aldehyde synthesis, the methods such as oxidation of hydrocarbons and reduction of acid halides are known, but these methods have problems such as poor reaction efficiency including critical oxidation conditions and stoichiometric formations of by-products such as halides, in addition to heavy environmental load.
As the methods to prepare aldehydes by reducing carboxylic acids, typically multi-step reactions are used, for example, converting carboxylic acids to acid chlorides and the like followed by partial reduction thereof, or converting the acids to alcohols followed by partial oxidation thereof.
An aldehyde synthesis reaction by catalytic hydrogenation of acid chlorides using molecular hydrogen as a hydrogen source in the presence of solid palladium catalysts is called the Rosenmund reduction, and is known to proceed almost quantitatively in various substrates by adding amines to the reaction system. This reaction has such advantages that hydrogen pressure can be the atmospheric pressure, but also disadvantages such as necessity of preparing acid chlorides and generation of acidic hydrochloric acid as a by-product. There is a report of hydrogenation in homogeneous system using palladium complexes. However, this reaction is limited to the substrates of aromatic carboxylic acid chlorides (A. Schoenberg and R. F. Heck, J. Am. Chem. Soc., 96,7761(1974)).
A method developed by former Mitsubishi Chemical Ind. (presently Mitsubishi Chemical Corp.) is an example of efficient hydrogenation of carboxylic acids using molecular hydrogen. This process provides aldehydes selectively in high yield by hydrogenation in vapor phase at high temperature (330~400° C.) in the presence of zirconia or chromic acid based solid catalysts (N. Ding, J. Kondo, K. Maruya, K. Domen, T. Yokoyama, N. Fujita, T. Maki, Catal., 17,309 (1993); laid-open Japanese Patent
1992-210936
(T. Yokoyama et al.); laid-open Japanese Paten
1987-108832
(T. Maki et al.); general review: T. Yokoyama, Monthly Report of Japan Chem. Ind. Association, April, 1997, p.14). Disadvantages of this method are difficulties in applications to the substrates with poor heat stability because high temperature is required for the reaction, and to a unit reaction in small-scale synthesis due to large sized plant being required.
The inventors of this invention have reported a method for preparation of aldehydes by reducing carboxylic anhydrides using molecular hydrogen under mild reaction conditions in the presence of zero valent palladium complex catalysts (Chem. Lett. 1995, 365). However, this method has problems in reaction efficiency such as necessity of preparation of acid anhydrides as raw materials in advance and generation of carboxylic acids equimolar to aldehydes as by-products.
BRIEF DESCRIPTION OF THE INVENTION
The invention provides a method for highly efficient preparation of aldehydes under mild reaction conditions by reducing carboxylic acids using molecular hydrogen.
The invention relates to a method for preparation of aldehydes in which organic carboxylic acids are reduced to corresponding organic aldehydes using molecular hydrogen in the presence of catalysts, wherein said reaction is performed in the presence of dehydrating agents.
MOST PREFERRED EMBODYMENT OF THIS INVENTION
In order to improve yield in the above mentioned preparation method for aldehydes using carboxylic anhydrides as raw materials (Chem. Lett. 1995, 365), the inventors have studied enthusiastically on an improvement of this reaction system. As the results, it was unexpectedly found that aldehydes was able to be obtained in high yield by converting corresponding carboxylic acids of raw materials to carboxylic anhydrides in this reaction system in the presence of dehydrating agents.
Thus, the invention features to obtain aldehydes in high yield by hydrogenating carboxylic acids with generation of acid anhydrides in the reaction system, in coexistence of dehydrating agents such as trimethylacetic anhydride.
There is no specific limitation on the dehydrating agents in the invention so long as they can convert carboxylic acids of raw materials to corresponding carboxylic anhydrides or mixture thereof in the reaction conditions, and more specifically, the compounds such as carboxylic anhydrides, dicarbonates or carbodiimides may be used, among which carboxylic anhydrides are preferred.
Carboxylic anhydrides to be used as dehydrating agent include linear or branched aliphatic carboxylic anhydrides having from 1 to 20, preferably from 1 to 10 carbon atoms; aromatic carboxylic anhydrides having from 6 to 20, preferably from 6 to 12 carbon atoms; and the like. Preferred carboxylic anhydrides include branched aliphatic carboxylic anhydrides having from 1 to 20, preferably from 1 to 10 carbon atoms. More typically, carboxylic anhydrides with sterically bulky substituents, such as trimethyl acetic anhydride, are more preferable.
Organic carboxylic acid as starting material of the invention may be any compound having carboxylic groups, and also may have other groups within the molecule that do not give any adverse effect on the reaction of the invention. When the carboxylic acids have groups with adverse effects on the reaction of the invention, the acids can be provided to the reaction after protecting the said groups with suitable protection groups generally used in peptide synthesis, etc.
Organic carboxylic acids as starting materials of the invention can be expressed by the following general formula (I),
R—COOH (I)
(wherein, R is an organic group)
and the organic group of R includes optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, optionally substituted cycloalkenyl, optionally substituted aryl, optionally substituted heteroaryl and the like.
These organic carboxylic acids may be monocarboxylic acids or polybasic acids having plural carboxyl groups such as dicarboxylic acids, tricarboxylic acids and the like.
Preferred alkyl groups in the general formula (I) above include linear or branched alkyl groups having from 1 to 30, preferably from 1 to 20, and more preferably from 5 to 15 carbon atoms; preferred alkenyl groups include linear or branched alkeny) groups having from 2 to 30, preferably from 2 to 20, and more preferably from 5 to 15 carbon atoms; preferred cycloalkyl groups include cycloalkyl groups of monocyclic, polycyclic or condensed ring system, having from 5 to 30, preferably from 5 to 20, and more preferably from 6 to 10 carbon atoms; preferred cycloalkenyl groups include aforementioned cycloalkyl groups having at least one unsaturated bond; preferred aryl groups include aryl groups of monocyclic, polycyclic or condensed ring system, having from 6 to 30, preferably from 6 to 20, and more preferably from 6 to 10 carbon atoms; and preferred heteroaryl groups include saturated or unsaturated heteroaryl groups of monocyclic, polycyclic or condensed ring system, containing at least one nitrogen, oxygen or sulfur atom, each ring having from 5 to 20, preferably from 5 to 10, and more preferably from 5 to 7 of ring members, wherein the groups may have cycloalkyl, cycloalkenyl or aryl groups described above in a condensed form. Or, R groups may be so-called aralkyl groups and may include aforementioned alkyl or alkenyl groups substituted by aryl or heteroaryl groups described above.
Alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl
Nagayama Kazuhiro
Yamamoto Akio
Adamson Edward J.
Corless Peter F.
Edwards & Angell LLP
Japan Science And Technology Corporation
Padmanabhan Sreeni
LandOfFree
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