Iron(III) bromide catalyzed bromination of 2-tert-butylpyrene and corresponding position-dependent aryl-functionalized pyrene derivatives

Feng, Xing; Hu, Jian-Yong; Tomiyasu, Hirotsugu; Tao, Zhu; Redshaw, Carl; Elsegood, Mark R. J.; Horsburgh, Lynne; Teat, Simon J.; Wei, Xian-Fu; Yamato, Takehiko

Abstract

The present work probes the bromination mechanism of 2-tert-butylpyrene (1), which regioselectively affords mono-, di-, tri- and tetra-bromopyrenes, by theoretical calculation and detailed experimental methods. The bromine atom may be directed to the K-region (positions 5- and 9-) instead of the more reactive 6- and 8-positions in the presence of iron powder. In this process, FeBr₃ plays a significant role to release steric hindrance or lower the activation energy of the rearrangement. The intermediate bromopyrene derivatives were isolated and confirmed by ¹H NMR spectrometry, mass spectroscopy and elemental analysis. Further evidence on substitution position originated from a series of aryl substituted pyrene derivatives, which were obtained from the corresponding bromopyrenes on reaction with 4-methoxy-phenylboronic acid by a Suzuki–Miyaura cross-coupling reaction. All position-dependent aryl-functionalized pyrene derivatives are characterized by single X-ray diffraction, ¹H/¹³C NMR, FT-IR and MS, and offered straightforward evidence to support our conclusion. Furthermore, the photophysical properties of a series of compounds were confirmed by fluorescence and absorption, as well as by fluorescence lifetime measurements.

Citation

Feng, X., Hu, J., Tomiyasu, H., Tao, Z., Redshaw, C., Elsegood, M. R. J., …Yamato, T. (2014). Iron(III) bromide catalyzed bromination of 2-tert-butylpyrene and corresponding position-dependent aryl-functionalized pyrene derivatives. RSC advances, 5(12), 8835-8848. https://doi.org/10.1039/C4RA12216J

• Acceptance Date: Dec 3, 2014
• Online Publication Date: Dec 4, 2014
• Publication Date: Dec 4, 2014
• Deposit Date: Jul 15, 2015
• Publicly Available Date: Jul 15, 2015
• Journal: RSC advances
• Print ISSN: 2046-2069
• Electronic ISSN: 2046-2069
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 5
• Issue: 12
• Pages: 8835-8848
• DOI: https://doi.org/10.1039/C4RA12216J
• Keywords: Iron(III) bromide; Bromination mechanism; Bromopyrenes; 2-tert-butylpyrene; Aryl-functionalized pyrene derivatives
• Public URL: https://hull-repository.worktribe.com/output/376453
• Publisher URL: http://pubs.rsc.org/en/Content/ArticleLanding/2015/RA/C4RA12216J#!divAbstract
• Additional Information: Author's accepted manuscript of an article which has been published in: RSC advances, 2015, v.5, issue 12.