Process for producing 5-methylindolines

Details Process for producing 5-methylindolines Process for producing 5-methylindolines

1999-10-07

2000-05-23

Stockton, Laura L.

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

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C07D20908

Patent

active

060667443

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/JP/98/01557 filed Apr. 3, 1998.


TECHNICAL FIELD

The present invention relates to a method for producing a 5-methylindoline which is very useful as an intermediate for medical and agricultural chemicals.


BACKGROUND ART

Heretofore, various methods have been proposed as methods for producing 5-methylindolines, but none of such methods has reached a level for practical industrial application.


DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a novel method for industrially producing a 5-methylindoline simply from a starting material which is industrially readily available.
To accomplish the above object, the present inventors have conducted extensive researches and as a result, have found it possible to carry out a reduction reaction to convert the formyl group at the 5-position of the indoline structure to a methyl group and a benzyl-removing reaction to remove the benzyl moiety at the 1-position of the indoline structure at the same time, by catalytically hydrogenating, in the presence of an inert solvent and a palladium catalyst, a 1-(substituted)benzyl-5-formylindoline (ka-3) which can be industrially produced by formylating the 5-position and converting the 1-position of the corresponding indoline to a (substituted)benzyl group. The present invention has been accomplished on the basis of this discovery.
Namely, the present invention has accomplished the above object by presenting a method for producing a 5-methylindoline represented by the formula: ##STR3## (wherein R.sup.1 is a hydrogen atom or a lower alkyl group), which comprises catalytically hydrogenating a 1-(substituted)benzyl-5-formylindoline represented by the formula: ##STR4## (wherein R.sup.1 is a hydrogen atom or a lower alkyl group, and R.sup.2 is a hydrogen atom, a lower alkyl group or a lower alkoxy group) in the presence of an inert solvent and a palladium catalyst.


BEST MODE FOR CARRYING OUT THE INVENTION

Now, the method of the present invention will be described in detail.
The method of the present invention is a novel method for producing a 5-methylindoline, which comprises catalytically hydrogenating a 1-(substituted)benzyl-5-formylindoline (ka-3) which is readily industrially available as a starting material, in the presence of an inert solvent and a palladium catalyst.
As the 1-(substituted)benzyl-5-formylindoline (ka-3) to be used as the starting material in the method of the present invention, any 1-(substituted)benzyl-5-formylindoline may be employed so long as R.sup.1 in the formula (ka-3) is a hydrogen atom or a C.sub.1-6 lower alkyl group, such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a pentyl group or a hexyl group, and R.sup.2 is a hydrogen atom; a C.sub.16 lower alkyl group, such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a pentyl group or a hexyl group; or a C.sub.1-6 lower alkoxy group, such as a methoxy group, an ethoxy group, a n-propoxy group, an isopropoxy group, a n-butoxy group, an isobutoxy group, a pentyloxy group or a hexyloxy group. As such a 1-(substituted)benzyl-5-formylindoline having R.sup.1 and R.sup.2 specifically, 1-benzyl-5-formylindoline, 1-benzyl-2-methyl-5-formylindoline or 1-(4'-methoxybenzyl)-2-methyl-5-formylindoline, may, for example, be mentioned. However, the starting material in the method of the present invention is not limited to such exemplified compounds.
As the palladium catalyst to be used in the method of the present invention, any palladium catalyst may be employed so long as it is used commonly in catalytic hydrogenation. In such a case, palladium may be used alone, or a simple substance or a hydroxide or the like of palladium, may be supported on a solid carrier such as active carbon, alumina, calcium carbonate, silica, diatomaceous earth or barium sulfate. In such a case, the proportion of palladium supported on the carrier, is not limited and may be suitably determined taking th

REFERENCES:
patent: 4159271 (1979-06-01), Sano et al.

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