Method for producing 1-menthol

Details Method for producing 1-menthol Method for producing 1-menthol

2001-05-07

2002-01-29

Shippen, Micahael L. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S350000, C568S377000

Reexamination Certificate

active

06342644

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to methods for the production of 1-menthol which is used as a medicament or perfume and of its intermediate pulegone.
BACKGROUND OF THE INVENTION
There are some reports on the hydrogenation reaction into pulegone from piperitenone which can be easily synthesized from mesityl oxide and methyl vinyl ketone. There are an example 1) reported by J. Solodar et al. in
J. Org. Chem.,
vol. 43, p. 1787, 1978, in which the hydrogenation is carried out using a Rh complex which uses cyclohexylanisylmethylphosphine as the ligand and an example 2) reported by P. L. Maux et al. in
Tetrahedron,
vol. 44, p. 1409, 1988, in which the hydrogenation is carried out using a diphenylneomenthylphosphine-Co complex.
Regarding reports on pulegol from pulegone, there is an example described by T. Ohkuma et al. in
Synlett,
p. 467, 1997, in which a catalyst system of (S)-BINAP-Ru-(S,S)-diphenylethylenediamine-KOH is used.
Regarding the synthesis of pulegone, the method 1) can synthesize it with a selectivity of about 90% but its optical purity is a low value of 33% ee, and DMF (dimethylformamide) is used in the reaction solvent, so that this method is not industrially applicable. Also, the method 2) can synthesize it only with a selectivity of 55% and an optical purity of 15% ee, so that they are not industrially applicable levels.
In addition, the ligand to be used in the synthesis of pulegol is a combination of (S)-BINAP and (S,S)-diphenylethylenediamine, and since optically active substances are used for both of them, this method has a problem of high catalyst cost.
SUMMARY OF THE INVENTION
The invention contemplates solving the illustrative problems shown in the following items 1) to 3).
1) Since there are three positions in piperitenone where hydrogenation can be effected, it is necessary for obtaining pulegone to increase position selectivity of hydrogenation. That is, it is necessary to select a catalyst, namely a ligand and a transition metal, which can attain superior selectivity and optical yield to those of conventionally used ligands including a monodentate phosphine such as cyclohexylanisylmethylphosphine, phenylanisylmethylphosphine or cyclohexyl-o-tert-butylphenylmethylphosphine and a bidentate phosphine such as DIPAMP: 1,2-bis[(o-methoxyphenyl)phenylphosphino]ethane or DIOP: 2,3-o-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane, and to examine solvent systems and additives which exert influences thereon.
2) Regarding preparation of pulegol from pulegone, significant result is obtained by a prior art ruthenium-diamine-potassium hydroxide system, so that it is expected to obtain equivalent catalytic activity and selectivity by changing it to an inexpensive catalyst.
3) The method to obtain menthol by hydrogenating pulegol can be carried out using a heterogeneous hydrogenation catalyst, but concern has been directed toward the development of a catalyst system having more higher selectivity.
DETAILED DESCRIPTION OF THE INVENTION
The following describes the invention in detail.
The piperitenone to be used in the invention can be prepared by allowing mesityl oxide to react with methyl vinyl ketone in the presence of potassium hydroxide (cf. JP-B-57-47168; the term “JP-B” as used herein means an “examined Japanese patent publication”) or by condensing mesityl oxide with 4-diethylamino-2-butanone.
In the invention, the 2-position olefin of piperitenone is hydrogenated as the first hydrogenation reaction. The reaction formula is shown below.
As the ligand to be used in the catalyst for hydrogenation of the 2-position olefin of piperitenone, there is an optically active phosphine represented by a general formula (2)
wherein R
1
represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms.
In this general formula (2) of the present invention. R
1
is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R
1
include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (2) include tertiary phosphines described in JP-A-61-63690 and JP-A-62-265293 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), and the following can be cited as illustrative examples.
2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl (to be referred to as “BINAP” hereinafter),
2,2′-bis[di(p-tolyl)phosphino]-1,1′-binaphthyl (to be referred to as “Tol-BINAP” hereinafter),
2,2′-bis[di(3,5-xylyl)phosphino]-1,1′-binaphthyl (to be referred to as “DM-BINAP” hereinafter),
2,2′-bis[di(3,5-di-tert-butylphenyl)phosphino]-1,1′-binaphthyl (to be referred to as “(t-Bu)2-BINAP” hereinafter),
2,2′-bis[di(4-methoxy-3,5-dimethylphenyl)phosphino]-1,1′-binaphthyl (to be referred to as “DMM-BINAP” hereinafter),
2,2′-bis(dicyclohexylphosphino)-1,1′-binaphthyl (to be referred to as “Cy-BINAP” hereinafter), and
2,2′-bis(dicyclopentylphosphino)-1,1′-binaphthyl (to be referred to as “Cp-BINAP” hereinafter).
As another ligand to be used in the catalyst for the first hydrogenation reaction, there is an optically active phosphine represented by a general formula (3)
wherein R
1
represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms.
In this general formula (3) of the present invention. R
1
is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R
1
include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (3) include tertiary phosphines described in JP-A-4-139140 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), and the following can be cited as illustrative examples.
2,2′-Bis{diphenylphosphino}-5,5′6,6′,7,7′,8,8′-octahydrobinaphthyl (to be referred to as “H
8
-BINAP” hereinafter),
2,2′-bis{di-p-tolylphosphino}-5,5′6,6′,7,7′,8,8′-octahydrobinaphthyl (to be referred to as “p-Tol-H
8
-BINAP” hereinafter),
2,2′-bis{di-(3,5-xylyl)phosphino}-5,5′6,6′,7,7′,8,8′-octahydrobinaphthyl (to be referred to as “DM-H
8
-BINAP” hereinafter), and
2,2′-bis{di-(4-methoxy-3,5-dimethylphenyl)phosphino}-5,5′6,6′,7,7′,8,8′-octahydrobinaphthyl (to be referred to as “DMM-H
8
-BINAP” hereinafter).
As still another ligand to be used in the catalyst for the first hydrogenation reaction, there is an optically active phosphine represented by a general

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