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.-Y., Tomiyasu, H., Tao, Z., Redshaw, C., Elsegood, M. R. J., Horsburgh, L., Teat, S. J., Wei, X.-F., & 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.
• Contract Date: Jul 15, 2015