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  • Palladium-catalyzed direct desulfitative C2 arylations of 3-halo-N-protected indoles using (hetero)arenesulfonyl chlorides.

Palladium-catalyzed direct desulfitative C2 arylations of 3-halo-N-protected indoles using (hetero)arenesulfonyl chlorides.

Organic & biomolecular chemistry (2016-05-14)
Anoir Hfaiedh, Hamed Ben Ammar, Jean-François Soulé, Henri Doucet
ABSTRACT

The direct arylation of N-protected 3-haloindole derivatives with benzenesulfonyl chlorides as coupling partners using 5 mol% of bis(acetonitrile)dichloropalladium(ii) catalyst and lithium carbonate as a base in 1,4-dioxane was investigated. We demonstrated that both iodo and chloro substituents at the indolyl C3 position act as temporary blocking groups allowing the formation of 2-arylindoles through a direct desulfitative arylation, followed by in situ dehalogenation. While, from 3-bromoindole derivatives, 2-aryl-3-bromoindoles were obtained without debromination, and could be converted into 2,3-diarylindoles through a second palladium coupling. This method allows one to prepare in a few steps a very wide variety of indole derivatives, which are of interest in the synthesis of bioactive molecules.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
3,4-Difluorobenzenesulfonyl chloride, 97%
Sigma-Aldrich
2-Bromo-4-(trifluoromethyl)benzenesulfonyl chloride, 97%
Sigma-Aldrich
2,5-Dibromobenzenesulfonyl chloride, 97%