Gold(I)-Catalyzed Benzylic C(sp3)-H Functionalizations: Product Bifurcation towards Indole[a]- and [b]-Fused Polycycles

02 September 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Phenylazides substituted by an (alkylphenyl)ethynyl group facilitate divergent benzylic sp3(C-H) functionalization in the presence of a JohnPhosAu catalyst, via N- or C-cyclization, resulting in indole-fused tetra- and pentacycles. The chemoselectivity is influenced depending on the counter-anion (SbF6 or BARF), the electron density of the alpha-imino gold(I) carbene, and the alkyl groups stabilizing the benzylic carbocation originating from a 1,5-hydride shift. An isotop-ic labeling experiment demonstrates the involvement of an indolylgold(I) species resulting in a tautomerization that is much faster than deauration is. The formation of a benzylic sp3(C-H) functionalization resulting in an indole-fused sev-en-membered ring is also demonstrated.

Keywords

gold catalysis
hydride shift
C-H bond functionalization
fused indoles
carbenes

Supplementary materials

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Description
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Supporting information
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Experimental section and NMR spectra
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