Synthesis 2017; 49(20): 4651-4662
DOI: 10.1055/s-0036-1589053
special topic
© Georg Thieme Verlag Stuttgart · New York

The Synthesis of Imidazo[1,2-f]phenanthridines, Phenanthro-[9,10-d]imidazoles, and Phenanthro[9′,10′:4,5]imidazo[1,2-f]-phenanthridines via Intramolecular Oxidative Aromatic Coupling

Kamil Skonieczny
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Email: dtgryko@icho.edu.pl
,
Jarosław Jaźwiński
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Email: dtgryko@icho.edu.pl
,
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Email: dtgryko@icho.edu.pl
› Author Affiliations
Financial support of our work from the National Science Centre, Poland (Grant Preludium UMO-2013/09/N/ST5/02974) and the Foundation for Polish Science (Grant number TEAM/2009-4/3) is gratefully acknowledged. The research leading to these results has received partial funding from the European Community’s Seventh Framework Programme under the TOPBIO project- grant agreement n. 264362.
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Publication History

Received: 09 April 2017

Accepted after revision: 22 May 2017

Publication Date:
26 June 2017 (online)


Published as part of the Special Topic Modern Strategies for Heterocycles Synthesis

Abstract

A short and efficient access to phenanthro[9,10-d]imidazoles, imidazo[1,2-f]phenanthridines, and phenanthro[9′,10′:4,5]imidazo[1,2-f]phenanthridines was achieved by the action of [bis(trifluoroacetoxy)iodo]benzene (PIFA) on properly substituted tetraaryl­-imidazoles. By pre-installing suitable electron-donating groups, it is possible to control the site of intramolecular oxidative aromatic coupling. In particular, by placing 3,4-dimethoxyphenyl and 3-methoxyphenyl moieties in close proximity, it was possible to direct the reaction into forming two biaryl linkages leading eventually to the formation of phenanthro[9′,10′:4,5]imidazo[1,2-f]phenanthridines. Starting from bis-aldehydes that are derivatives of thieno[3,2-b]thiophene and fluorene enabled the synthesis of π-expanded imidazoles bearing 8-9 conjugated rings. By placing a dimethoxynaphthalene unit on the imidazole scaffold, we have directed the oxidative coupling reaction towards closing a five-membered ring with concomitant removal of methoxy group leading to formation of an α,β-unsaturated ketone. All resulting π-expanded imidazoles display blue emission, and the fluorescence quantum yields in some cases reaches 0.9.

Supporting Information