Process for the synthesis of substituted indolenines

Details Process for the synthesis of substituted indolenines Process for the synthesis of substituted indolenines

1975-04-04

1977-12-13

Love, Ethel G.

Chemistry of carbon compounds

Miscellaneous organic carbon compounds

C-metal

26032612R, 26032616, 2604299, 260566R, C07D20904

Patent

active

040628655

ABSTRACT:
A process for the preparation of substituted indolenines of the formula: ##STR1## wherein R is hydrogen, alkyl, aryl or cycloalkyl, halogen, or a functional group selected from among cyano, hydroxyl, alkoxy, nitro or sulphonic groups, and wherein R.sub.1, R.sub.2 and R.sub.3 are the same, or different, and are selected from alkyl, aryl or cycloalkyl radicals, comprising reacting in the presence of an organic solvent an aromatic amine of the formula: ##STR2## with a tertiary hydroxyketone of the formula: ##STR3## wherein R, R.sub.1, R.sub.2 and R.sub.3 have the same meanings as defined above, in the presence of a catalyst selected from mineral acids, organic acids, Lewis acids or ionic exchange resins in acid form, and wherein said aromatic amine is slightly in excess, to form first an imine of the formula: ##STR4## under reaction conditions wherein the solvent is removed by azeotropic distillation, and thereafter continuing the reaction to remove water and cyclizing to the desired indolenines. In a preferred embodiment, 2,3,3-trimethylindolenine is prepared by reacting an excess of aniline with 3-methyl-3-hydroxybutan-2-one in the presence of ZnCl.sub.2 as catalyst utilizing benzene as solvent. The substituted indolenines obtained are useful in production of dyes and other compounds useful in the dyeing and photographic industries.

REFERENCES:
patent: 3671214 (1972-06-01), Alt
Garry, M., Annales de Chimi, vol. 17, pp. 61-97; pertinent pp. 66-72 (Jan.-June 1942).
Elderfield, Heterocyclic Compounds, vol. 3, pp. 22-35 (1952).
Houlihan, "Indoles," part one, pp. 317-375; pertinent pp. 319 and 324-326 (1972).
Sundberg, "The Chem. of Indoles," p. 168 (1970).

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