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Synthesis 2019; 51(04): 933-943
DOI: 10.1055/s-0037-1610666
DOI: 10.1055/s-0037-1610666
paper
Imidazole-Fused Enediynes by Selective C5–C4 Alkynylations of 4,5-Dibromoimidazoles
This work was supported by the Regione Toscana under POR-CREO 2014-2020 (project ‘COOLSUN’), the Università di Pisa under PRA 2017 (project No. PRA_2017_28).Further Information
Publication History
Received: 18 August 2018
Accepted after revision: 01 October 2018
Publication Date:
30 October 2018 (online)
Abstract
An efficient synthesis of symmetrical 1,2-disubstituted 4,5-dialkynylimidazoles by Sonogashira alkynylation of the corresponding 4,5-dibromo derivatives was developed. Moreover, through a careful tuning of the palladium ligand, unsymmetrical 1,2-disusbtituted 4,5-dialkynylimidazoles were also prepared through a regioselective C5 alkynylation of 4,5-dibromoimidazoles, followed by a second alkynylation involving the 4-bromo derivatives so obtained. This interesting class of imidazole-fused enediynes is also able to give thermal Bergman cycloaromatization (BC), as proved by DSC experiments.
Key words
imidazoles - Sonogashira reaction - regioselectivity - enediynes - Bergman cyclization - palladium - copper - cross-couplingSupporting Information
- Supporting information (Table S1, copies of NMR spectra for compounds 4a–e, 5a–e, 9a–d, 10a, and DSC thermograms for compounds 5a–d and 9a–c) for this article is available online at https://doi.org/10.1055/s-0037-1610666.
- Supporting Information
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