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. 2017 Jan 3;2017(1):203-207.
doi: 10.1002/ejoc.201601336. Epub 2017 Jan 6.

A Cu-Catalysed Radical Cross-Dehydrogenative Coupling Approach to Acridanes and Related Heterocycles

Timothy E Hurst  1 , Richard J K Taylor  1
Affiliations

A Cu-Catalysed Radical Cross-Dehydrogenative Coupling Approach to Acridanes and Related Heterocycles

Timothy E Hurst et al. European J Org Chem. .

Abstract

The synthesis of acridanes and related compounds through a Cu-catalysed radical cross-dehydrogenative coupling of simple 2-[2-(arylamino)aryl]malonates is reported. This method can be further streamlined to a one-pot protocol involving the in situ fomation of the 2-[2-(arylamino)aryl]malonate by α-arylation of diethyl malonate with 2-bromodiarylamines under Pd catalysis, followed by Cu-catalysed cyclisation.

Keywords: Acridanes; Copper; Cross‐coupling; Dehydrogenation; Homogeneous catalysis; Nitrogen heterocycles; One‐pot reaction.

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Figures

Figure 1
Figure 1
Examples demonstrating the utility of acridanes.
Scheme 1
Scheme 1
Approaches for the synthesis of acridanes.
Scheme 2
Scheme 2
Modular synthesis of cyclisation precursors 15a–j.
Scheme 3
Scheme 3
Scope of the Cu‐catalysed synthesis of acridanes. [a] 16a was obtained in 83 and 84 % yield when Cu(2‐ethylhexanoate)2 (5 mol‐% and 2 mol‐%) were used, respectively. [b] Cu(2‐ethylhexanoate)2 (2.5 equiv.) and DIPEA (2.5 equiv.) were used under an atmosphere of argon.
Scheme 4
Scheme 4
Further derivatisation of acridanes obtained from oxidative coupling.
Scheme 5
Scheme 5
Retrosynthesis of acridanes 16 through a one‐pot α‐arylation–cyclisation process.
Scheme 6
Scheme 6
Synthesis of 2‐halodiarylamines 21a–d.
Scheme 7
Scheme 7
Scope of the one‐pot α‐arylation–cyclisation approach to acridanes.
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