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

International audienceThe 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

Palladium-catalyzed regioselective C-H bond arylations at the C3 position of ortho-substituted fluorobenzenes

International audienceThe influence of an ortho-substituent on fluorobenzene derivatives for palladium-catalyzed C-H bond arylation has been explored. In the presence of 2-bromo, 2-chloro and 2-methoxy substituents, the reaction proceeds nicely using a diphosphine-palladium catalyst and potassium acetate/dimethylacetamide (PivOK/DMA) as the catalytic system. In all cases, a regioselective arylation at the other ortho-position to the fluorine atom (C3) was observed. A variety of electron-withdrawing substituents on the aryl bromide coupling partner, such as formyl, nitro, nitrile, and also heteroaryl bromides, was tolerated. Moreover, tri(hetero) aryl derivatives containing a fluorobenzene as the central unit have been prepared from 2-bromofluorobenzene through palladium-catalyzed-successive C-H bond (hetero)arylations