Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1998-06-19
2000-06-27
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568749, 568771, 568800, C07C 3760
Patent
active
060808950
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an improved process for preparing a catechol derivative represented by a generic formula (1) mentioned later, which constitutes a basic structure of a compound useful especially for pharmaceuticals and agricultural chemicals and is used as an intermediate thereof.
BACKGROUND ART
Monoalkylcatechol derivatives are used as intermediates for pharmaceuticals and agricultural chemicals. The method of preparing them by alkyl-etherification of only a hydroxy group on one side of a corresponding catechol derivative and the method of preparing them by hydroxylation of a corresponding alkoxybenzene derivative have been mainly known. As to the former, the alkyl-ether method by dialkyl sulfate (Japanese Patent Publication (A) No. 112485/1993), and the alkyl-ether method by an alcohol and an acid catalyst (Japanese Patent Publication (A) No. 305546/1992) are illustrated. As to the latter, the method by reaction with hydrogen peroxide under formic acid (Bull. Chem. Soc. Jpn., 1989, 62, 1652-1657), the method by reaction with Fe (IV)-EDTA ascorbic acids (J. Mol. Catal. 1982, 14, 333-340), the method by reaction with peracetic acid (Nippon Kagaku Kaishi 1979, 370-374), and the method of synthesis by photo oxidization under Lewis acid (Chem. Lett., 1972, 179-180) are illustrated.
However, the above known methods are generally inferior in a yield and a position-selectivity. Accordingly, the mixture of regioisomers forms and it is difficult to separate each other so that these methods are not suitable for preparing the intermediates of pharmaceuticals and agricultural chemicals which require high purity. Expensive reagents and raw materials which are difficult to obtain, are sometimes used and therefore, these known methods are not satisfied in the industrial production.
The present inventors engaged extensively in solving the above problems, and have found a new process for preparation of a catechol derivative almost without any by-products and in a high yield and that in a high purity almost without contamination of regioisomers.
DISCLOSURE OF INVENTION
The present invention provides to a process for preparing a catechol derivative represented by the following generic formula (1), ##STR2## and is characterized in preparing the catechol derivative by the following three steps:
(I) a step for preparing a salicylaldehyde derivative represented by the following generic formula (3), ##STR3## by reacting a phenol derivative represented by the following formula (2), ##STR4## with a base and paraformaldehyde in the presence of SnCl.sub.2 and/or SnCl.sub.4 in an organic solvent at 60-85.degree. C. until attaining the conversion to 30-80% and then completing the reaction at 95-105.degree. C.;
(II) a step for preparing a formyl ether represented by the following generic formula (4), ##STR5## by treating a salicylaldehyde derivative of the formula (3) by an alkylating agent in the presence of a base in water and/or an organic solvent to introduce a hydroxy protective group; and
(III) a step for preparing a catechol derivative represented by the formula (1) by oxidizing a formyl ether of the formula (4) in water and/or an organic solvent, and then hydrolyzing the product in the presence of an acid or a base.
In the above formulae (1)-(4), R is alkyl, cycloalkyl, aralkyl, alkoxy, halogen atom, allyl, or aryl, R.sup.1 is a hydroxy protective group, which is selected from known hydroxy protective groups, and said protective group is preferable one which is not eliminated by oxidation and hydrolysis in the course of the reaction of the step (III). Examples of said protective group are alkyl, benzyl, o-nitrobenzyl, p-methoxybenzyl, and allyl.
The above each step is explained in detail.
In the step (I), as the alkyl in R of a phenol derivative of the formula (2), alkyls blanched or not blanched having 1-4 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl, etc.; as the cycloalkyl in the R, cycloalkyls having 3-6 carbon atoms, such as cyclopropyl, cyclobutyl,
REFERENCES:
patent: 4151201 (1979-04-01), Casnati et al.
Greene, Protective Groups in Organic Synthesis, p. 93, 1981.
J. Org. Chem. 1984, 49, pp. 4740-4741.
Journal of Molecular Catalysis, 14 (1982), pp. 333-340.
Bull. Chem. Soc. Jpn., 62, pp. 1652-1657 (1989).
Chemistry Letters, pp. 179-180, 1972.
J. Chem Soc., Perkin Trans I, pp. 1862-1865 (1980).
J. Chem. Soc., Perkin Trans I, pp. 1353-1354 (1974).
Indian Journal of Chemistry vol. 23B, May, 1984, pp. 474-475.
J Chem. Soc., Perkin Trans I, pp. 1823-1831 (1994).
Nippon Kagaku Kaishi 1979, (3), pp. 370-374.
Furukawa Yoshiro
Takenaka Keishi
Daiso Co. Ltd.
Geist Gary
Padmanabhan Sreeni
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