β-Carboline Amides as Intrinsic Directing Groups for C(sp2)-H Functionalization.
Hélène M-F ViartAndreas BachmannWilliam KayitareRichmond SarpongPublished in: Journal of the American Chemical Society (2017)
Many site-selective palladium-catalyzed C-H functionalization methods require directing groups. We report here β-carboline amides as intrinsic directing groups for C(sp2)-H functionalization. Various substrates including the natural product alangiobussinine and the marinacarboline core structure were functionalized using carboline-directed δ-C(sp2)-H alkynylations. This transformation proceeds under mild conditions and is compatible with a wide variety of β-arylethamines. δ-Alkynylation of β-arylethamines via a six-membered palladacycle is favored over γ-C(sp2)-H bond functionalization when both positions are accessible. The versatility of β-carboline amides as directing groups is evidenced by other δ-C(sp2)-H functionalizations such as alkenylation, arylation, and C-N bond formation.
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