Gold(I)-Catalyzed Benzylic C(sp3)−H Functionalizations: Divergent Synthesis of Indole[a]- and [b]-Fused Polycycles** |
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Authors: | Luca C Greiner Dr Norihito Arichi Prof Dr Shinsuke Inuki Prof Dr Hiroaki Ohno |
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Institution: | Graduate School of Pharmaceutical Sciences, Kyoto University Sakyo-ku, Kyoto, 606-8501 Japan |
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Abstract: | Phenyl azides substituted by an (alkylphenyl)ethynyl group facilitate benzylic sp3(C−H) functionalization in the presence of a JohnPhosAu catalyst, resulting in indole-fused tetra- and pentacycles via divergent N- or C-cyclization. The chemoselectivity is influenced depending on the counter-anion, the electron density of the α-imino gold(I) carbene, and the alkyl groups stabilizing the benzylic carbocation originating from a 1,5-hydride shift. An isotopic labeling experiment demonstrates the involvement of an indolylgold(I) species resulting from a tautomerization that is much faster than the deauration. The formation of a benzylic sp3(C−H) functionalization leading to an indole-fused seven-membered ring is also demonstrated. |
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Keywords: | C−H Bond Functionalization Carbenes Fused Indoles Gold Catalysis Hydride Shift |
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