Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1981-11-10
1984-04-17
Daus, Donald G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
548508, C07D20908
Patent
active
044436157
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a process for preparing indoles. More particularly, it relates to a process for preparing indoles by a vapor phase reaction of anilines with glycols or oxides in the presence of a solid acid catalyst having dehydrating and dehydrogenating activities.
TECHNICAL BACKGROUND
Indoles are useful as starting materials for tryptophan, aromatics, medicines, agricaltural chemicals, stabilizers for polymers, and the like. Various methods have been known for preparation of indoles by a vapor phase reaction. For example, Japanese Patent Publication (unexamined) No. 78163/1973 discloses that indoles are prepared by contacting 2-alkylanilines at 500.degree. to 750.degree. C. with an iron oxide catalyst containing an alkali metal compound. Japanese Patent Publication (unexamined) No. 57966/1973 discloses that indoles are prepared by contacting o-nitroalkylbenzene at 300.degree. to 550.degree. C. with a catalyst containing ruthenium, palladium or platinum. Further, Japanese Patent Publication (unexamined) No. 65266/1977 discloses that indoles are prepared by contacting phenylhydrozines and a carbonyl compound at 300.degree. C. with a Lewis acid (e.g., zinic chloride). Furthermore, Chemical Abstracts, Vol. 62 (1965), 16174h discloses that indole are prepared by contacting aniline and ethanol with an alumina catalyst or an iron oxide-alumina catalyst. Additionally, Chemical Abstracts, Vol. 63 (1965), 11477 g discloses that indole are prepared by contacting aniline and acetylene at 620.degree. to 700.degree. C. with an iron oxide-alumina catalyst. However, the methods described in Japanese Patent Publication (unexamined) No. 78163/1973 and Chemical Abstracts, Vol. 63 (1965), 11477 g are disadvantageous in that the vapor phase reaction must be carried out at a temperature higher than 500.degree. C. In the method described in Japanese Patent Publication (unexamined) No. 57966/1973 it is necessary to use an expensive noble metal catalyst, and the methods described in Japanese Patent Publication (unexamined) Nos. 57966/1973 and 65266/1977 require the use of expensive o-nitro-alkylbenzene or phenylhydrazines as the starting material. Further, the methods described in Japanese Patent Publication (unexamined) Nos. 78163/1973 and 57966/1973, Chemical Abstracts, Vol. 62 (1965), 16174h an ibid. Vol. 63 (1965), 11477 g are disadvantageous in that N-substituted indoles can not be prepared directly.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a method for preparing various indoles including N-substituted indoles from anilines and glycols (or oxides) both of which are less expensive and readily available in the market. Another object of the invention is to provide a method for preparing indoles by carrying out a vapor phase reaction at such a relatively low temperature as 250.degree. to 400.degree. C. Other object of the invention is to provide a method for preparing indoles advantageously in an industrial scale by using a conventional solid acid catalyst instead of such an expensive catlyst as the noble metal catalyst. These and further objects of the invention will become apparent from the following description.
DISCLOSURE OF THE INVENTION
As a result of various inventigations, we have now found that indoles can be readily prepared by reacting anilines with glycols or oxides in the vapor phase in the presence of a solid acid catalyst having dehydrating and dehydrogenating activities. Namely, according to the present invention, an indole of the formula: ##STR4## wherein R.sup.1 stands for hydrogen, alkyl, aryl or aralkyl, R.sup.2 stands for alkyl or alkoxy, R.sup.3 and R.sup.4 are the same or different and stand for hydrogen or alkyl, and n stands for an integer of 0 to 4, can be prepared by reacting an aniline of the formula: ##STR5## wherein R.sup.1, R.sup.2 and n are the same as defined above, with either a glycol of the formula: ##STR6## wherein R.sup.3 and R.sup.4 are the same as defined above, and R.sup.5 and R.sup.6 are the same or different and stand
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Matsuoka Manabu
Tokuda Yoshikazu
Tsuchiya Michihiro
Bierman Jordan B.
Bierman Linda
Daus Donald G.
Hendricks G.
Tanabe Seiyaku Co. Ltd.
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