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Dihydroheteroanthracene_Amination_ChemRxiv_combined.pdf (2.46 MB)

Uncatalysed Oxidative C‒H Amination of 9,10-Dihydro-9-Heteroanthracenes: A Mechanistic Study

preprint
submitted on 14.02.2019, 10:45 and posted on 14.02.2019, 16:10 by Nicolaas P. van Leest, Lars grooten, Jarl Ivar van der Vlugt, Bas de Bruin
A new method for the one-step C‒H amination of xanthene and thioxanthene with sulfonamides is reported, without the need for any metal catalyst. A benzoquinone is employed as a hydride (or two-electron and one-proton) acceptor. Moreover, a previously unknown and uncatalysed reaction between iminoiodanes and xanthene, thioxanthene and dihydroacridines (9,10-dihydro-9-hetero-anthracenes or dihydroheteroanthracenes) is disclosed. The reactions proceed via hydride transfer from the heteroarene substrate to the iminoiodane or benzoquinone, followed by conjugate addition of the sulfonamide to the oxidized heteroaromatic compounds. These findings may have important mechanistic implications for metal-catalysed C‒H amination processes involving nitrene transfer from iminoiodanes to dihydroheteroanthracenes. Due to the weak C‒H bond, xanthene is an often-employed substrate in mechanistic studies of C‒H amination reactions, which are generally proposed to proceed via metal-catalysed nitrene insertion, especially for reactions involving nitrene or imido complexes that are less reactive (i.e. less strongly oxidizing). However, these substrates clearly undergo non-catalysed (proton-coupled) redox coupling with amines, thus providing alternative pathways to the widely assumed metal-catalysed pathways.

Funding

The Netherlands Organisation for Scientific Research (NWO TOP-Grant 716.015.001)

History

Email Address of Submitting Author

b.debruin@uva.nl

Institution

University of Amsterdam

Country

The Netherlands

ORCID For Submitting Author

0000-0002-3482-7669

Declaration of Conflict of Interest

The authors declare no conflicts of interest.

Version Notes

First submission

Exports