Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-09-26
2003-07-29
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06600079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing 5-arylpentanols that are useful as synthetic intermediates of perfume, medicaments, agricultural chemicals and the like from pyran compounds.
2. Description of the Prior Art
Hitherto, there have been known, as a method for obtaining 5-arylpentanols, a method for producing a 5-aryl-3-methylpentanol by hydrogenolysis of 2-phenyl-4-methylenepyran using a metal catalyst such as palladium and an acid substance such as an inorganic proton acid or acidic diatomaceous earth (Switzerland Patent No.655932) and a method for producing 5-phenylpentanol by hydrogenolysis of 2-phenyltetrahydropyran in an acetic acid solution containing perchloric acid in the presence of a palladium catalyst (J. Am. Chem. Soc., 70, 1490~1492 (1948)).
On the other hand, there is no prior art for effectively producing a 5-arylpentanol through hydrogenolysis of a pyran compound in the absence of an acidic substance. This is because the rate of hydrogenolysis reaction is significantly decreased if an acidic substance is not used.
However, a process using an acidic substance is not industrially favorable because a large amount of by-products is produced, the yield of a 5-arylpentanol is not necessarily high, there is a problem with regard to corrosion of process equipment owing to the use of the acidic substance, and waste is increased, thereby increasing an environmental load.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for producing a 5-arylpentanol in a high yield with little amount of by-products.
Another object of the invention is to provide a process for producing a 5-arylpentanol which does not bring about a problem with regard to corrosion of process equipment and is industrially satisfactory.
The present inventors have found, after intensive researches, that the aimed product can be obtained in a high yield and industrially satisfactorily while suppressing production of by-products without using a special corrosion-resistant equipment by effecting hydrogenolysis in the presence of a supported catalyst of two or more elements selected from the noble metals in Group VIII in the periodic table and/or an acidic-type palladium-supporting catalyst, and have completed the invention.
There is thus provided a process for producing a 5-arylpentanol of formula (2):
wherein,
R
1
represents an aryl group which may be substituted with one or two or more of an alkyl or alkoxy group and has 6 to 12 carbon atoms in total,
R
3
represents a hydrogen atom, or an alkyl or alkenyl group of 1 to 6 carbon atoms, and
R
4
represents R
2
defined below when R
2
is a monovalent group or represents R
2
H when R
2
is a divalent group,
which comprises effecting hydrogenolysis of a pyran compound of formula (1):
wherein,
R
1
and R
3
are as defined above,
R
2
represents a hydrogen atom, an alkyl or alkenyl group of 1 to 6 carbon atoms, or an alkylidene or alkenylidene group of 1 to 6 carbon atoms, and
a dotted line ( - - - ) represents a possible bond and any one of the three bonds represented by dotted lines and solid lines is a double bond, in the presence of one or more catalysts selected from (a) a catalyst carrying two or more elements selected from noble metals in Group VIII in the periodic table and (b) an acid type palladium-supporting catalyst.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the pyran compounds of the formula (1), R
1
is preferably an aryl group having in total 6 to 12 carbon atoms which may be substituted with one or two or more of alkyl or alkoxy groups each having 1 to 6 carbon atoms. The aryl group includes phenyl group and naphthyl group, and is preferably phenyl group. R
1
is particularly preferably phenyl, or o-, m- or p-tolyl, and most preferably phenyl.
R
2
is preferably a hydrogen atom or an alkyl or alkylidene group having 1 to 6 carbon atoms, more preferably a hydrogen atom, methyl group or methylene group, and most preferably a hydrogen atom or methyl group.
R
3
is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and particularly preferably a hydrogen atom or methyl group.
Examples of the pyran compounds include 6-phenyl-4-methyl-5,6-dihydro-2H-pyran, 6-phenyl-2,4-dimethyl-5,6-dihydro-2H-pyran, 6-p-tolyl-4-methyl-5, 6-dihydro-2H-pyran, 2-phenyl-4-methylenetetrahydro-2H-pyran, and 2-phenyl-4-methyl-5,6-dihydro-2H-pyran.
One of the preferred embodiments of the present invention is a process for producing a 5-arylpentanol of formula (2a):
wherein,
R
1
represents an aryl group which may be substituted with one or two or more of an alkyl or alkoxy group and has 6 to 12 carbon atoms in total, and
R
2a
and R
3
may be the same or different and represent a hydrogen atom, or an alkyl or alkenyl group of 1 to 6 carbon atoms,
which comprises effecting hydrogenolysis of a 5,6-dihydro-2H-pyran compound of formula (1a):
wherein, R
1
, R
2a
and R
3
are as defined above, in the presence of one or more catalysts selected from (a) a catalyst carrying two or more elements selected from noble metals in Group VIII in the periodic table and (b) an acid type palladium-supporting catalyst.
In formula (1a), preferred groups as R
1
and R
3
are the same as those described for R
1
and R
3
in formula (1). R
2a
is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or methyl group.
In the catalyst carrying two or more elements selected from noble metals in Group VIII in the periodic table, the noble metals include palladium, platinum, rhodium and ruthenium. Carriers for the noble metals include carbon, alumina, silica gel, barium sulfate, zeolite and calcium carbonate. The catalyst may be two or more noble metals supported on one kind of carrier, or a mixture of two or more kinds of carriers each carrying one kind of noble metal. The amount of each noble metal supported on a carrier is preferably 0.1 to 10% by weight, and more preferably 0.2 to 8% by weight of the catalyst. Total amount of two or more noble metals supported on carrier(s) is preferably 1 to 20% by weight, more preferably 2 to 10% by weight of the catalyst. These catalysts can be obtained by a well known method, for example by an impregnation supporting method (“Catalyst Preparation Chemistry” edited by Atsumu Ozaki, published by Kodansha) in which a carrier is impregnated with a metal and the resulting carrier is reduced with hydrogen at a higher temperature. Alternatively, commercial products may be used as they are. Examples of such commercial products include Palladium-Platinum-Carbon powder, Palladium-Carbon Powder, Platinum-Carbon Powder, and Ruthenium-Carbon Powder each manufactured by N. E. Chemcat Corporation.
The acid type palladium-supporting catalyst used in the present invention means such a solid palladium catalyst in which palladium is supported on at least one carrier selected from alumina, silica gel, barium sulfate, zeolite and calcium carbonate and which shows a pH of less than 7, preferably 2 to 6, particularly preferably 3 to 5.5 when it is dispersed in water. For example, when 4 g of the catalyst is dispersed in 30 g of pure water for 5 minutes, the resulting water has a pH of less than 7, preferably 2 to 6, particularly preferably 3 to 5.5. If the pH of the catalyst is not less than 7, production rate of a 5-arylpentanol significantly decreases. The amount of palladium in the catalyst is preferably 0.5 to 10% by weight, particularly 2 to 10% by weight of the catalyst. Such catalysts can be obtained by a well known method, for example by impregnating a carrier with a metal according to an impregnation supporting method (“Catalyst Preparation Chemistry” edited by Atsumu Ozaki, published by Kodansha), and reducing the resulting carrier with hydrogen at a higher temperature. Alternatively, commercially available catalysts may be used. For example, among commercially available palladium-carbon powders manufactured by N. E. Chemcat Corporation, those having a pH in the above-mentioned range may be
Tanaka Shigeyoshi
Umada Akira
Kao Corporation
Shippen Michael L.
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