Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1995-12-27
1997-06-10
Ivy, C. Warren
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
546343, 546340, C07D21330
Patent
active
056377169
DESCRIPTION:
BRIEF SUMMARY
This application is a #35 U.S.C. 371 National Stage filing of PCT/JP94/01230 published as WO 95/04044 on Feb. 9, 1995.
INDUSTRIAL FIELD OF APPLICATION
The present invention relates to processes for the preparation of important intermediates for the synthesis of the benzothiazole derivatives which are disclosed in EP-A 507318 and are useful for the prevention and treatment of diseases for which an inhibitory action against the production of leukotriene and thromboxane is efficacious.
PRIOR ART
The above European Patent (EP-A 507318) also discloses a process for the preparation of a compound (VI) similar to pyridynylmethyl-1,4-benzoquinone derivatives represented by the general formula (IV). This process is, as represented by the following reaction formula (wherein R.sup.5 and R.sup.6 represent the same or different from each other a hydrogen atom, a lower alkyl group or a lower alkoxy group; and R.sup.7 represents a lower alkyl group), one which comprises introducing a pyridylmethanol group into a dimethoxybenzene derivative as a starting material and oxidizing the resulting product with diammonium cerium (IV) nitrate: ##STR2##
The 2,5-dimethoxybenzene derivative used as the starting material in the process of the prior art is one prepared by methylating a hydroquinone derivative as represented by the following reaction formula (wherein R.sup.5 and R.sup.6 are each as defined above) for the purpose of protecting the hydroxyl groups of the hydroquinone derivative from the influence of the reagent (i.e., n-BuLi) used in the subsequent introduction of a pyridylmethanol group. However, this methylation is an entirely useless step and industrially disadvantageous, because the methyl groups (introduced as the protecting groups) are removed by oxidation in the oxidation step conducted after the introduction of a pyridiylmethanol group for preparing an objective 1,4-benzoquinone derivative. Further, the oxidation conditions of the methoxy derivative (with the protected hydroxyl groups) are restricted more severely than those of the hydroxy derivative, because the methoxy derivative is more resistant to oxidation than the hydroxy derivative. Thus, the methoxy derivative is disadvantageous also in this respect. Under these circumstances, it has been expected to establish an industrial process for introducing a pyridylmethanol group into a hydroquinone derivative without the necessity for protecting the hydroxyl groups of the derivative and uncostly conditions of the oxidation subsequent to the introduction. ##STR3##
DISCLOSURE OF THE INVENTION
The inventors of the present invention have made intensive studies on the introduction of a pyridylmethyl group into a hydroquinone derivative represented by the general formula (I) without the necessity for protecting the hydroxyl groups of the derivative. As a result of the studies, they have found a process for the preparation of a pyridylmethylhydroquinone derivative represented by the general formula (III) which comprises reacting a hydroquinone derivative represented by the general formula (I) with a pyridinecarboxaldehyde represented by the general formula (II) or an alkyl acetal derivative represented by the general formula (II') in the presence of an acid without the necessity for protecting the hydroxyl groups of the hydroquinone derivative. Further, they have also established a process for preparing a pyridylmethyl-1,4-benzoquinone derivative (IV) through oxidation under inexpensive conditions. Thus, the present invention has been accomplished.
The present invention will now be described in detail. ##STR4## (wherein R.sup.1 represents a hydrogen atom, a methyl group or a methoxy group; R.sup.2 and R.sup.3 represent the same or different from each other a hydrogen atom or a methyl group; R.sup.4 represents a hydrogen atom or a lower alkyl group; R' represents a lower alkyl group; and X represents a hydrogen atom, a lower alkyl group, a lower alkoxy group or a halogen atom).
In this step, a pyridylmethyl derivative (III) is prepared by condensing a hydroquinon
REFERENCES:
patent: 4043790 (1977-08-01), Krumkalns
patent: 4111945 (1978-09-01), Jarque et al.
patent: 5541331 (1996-07-01), Murugan et al.
Summerford et al "The Hydrolysis of Some Quinone Oxines" vol. 66--pp. 1330-1331 (1994).
Shimizu et al--1992 The Chemical Society of Japan vol. 65, No. 6--pp. 1522-1526 (1992).
Furukawa Ken
Komatsu Yuuki
Minami Norio
Nishimura Hiroshi
Yamagishi Yoji
Eisai Chemical Co., Ltd.
Eisai Co. Ltd.
Ivy C. Warren
Smith Lyman H.
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