Abstract: Two molecules of indole derivative, e.g. indole-5-carboxylic acid, reacted with one molecule of thiol, e.g. 1,2-ethanedithiol, in the presence of trifluoroacetic acid to yield adducts such as 3-[2-(2-amino-5-carboxyphenyl)-1-(2-mercaptoethylthio)ethyl]-1Hindole-5-carboxylic acid. Parallel formation of dimers, such as 2,3-dihydro-1H,1'H-2,3'-biindole-5,5'-dicarboxylic acid and trimers, such as 3,3'-[2-(2-amino-5-carboxyphenyl) ethane-1,1-diyl]bis(1H-indole-5-carboxylic acid) of the indole derivatives was also observed. Reaction of a mixture of indole and indole-5-carboxylic acid with 2-phenylethanethiol proceeded in a regioselective way, affording 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H-indole-5-carboxylic acid. An additional product of this reaction was 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-2,3-dihydro-1H,1'H-2,3'-biindole-5'-carboxylic acid, which upon standing in DMSO-d6 solution gave 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H,1'H-2,3'-biindole-5'-carboxylic acid. Structures of all compounds were elucidated by NMR, and a mechanism for their formation was suggested.
Keywords: Side reaction; oligomerization of indole derivatives; incorporation of thiols; regioselectivity; NMR study
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Mutulis, F.; Gogoll, A.; Mutule, I.; Yahorava, S.; Yahorau, A.; Liepinsh, E.; Wikberg, J.E. Oligomerization of Indole Derivatives with Incorporation of Thiols. Molecules 2008, 13, 1846-1863.
Mutulis F, Gogoll A, Mutule I, Yahorava S, Yahorau A, Liepinsh E, Wikberg JE. Oligomerization of Indole Derivatives with Incorporation of Thiols. Molecules. 2008; 13(8):1846-1863.
Mutulis, Felikss; Gogoll, Adolf; Mutule, Ilze; Yahorava, Sviatlana; Yahorau, Aleh; Liepinsh, Edvards; Wikberg, Jarl E. 2008. "Oligomerization of Indole Derivatives with Incorporation of Thiols." Molecules 13, no. 8: 1846-1863.