Issue 9, 2017

Borylation of fluorinated arenes using the boron-centred nucleophile B(CN)32− – a unique entry to aryltricyanoborates

Abstract

The potassium salt of the boron-centred nucleophile B(CN)32− (1) readily reacts with perfluorinated arenes, such as hexafluorobenzene, decafluorobiphenyl, octafluoronaphthalene and pentafluoropyridine, which results in KF and the K+ salts of the respective borate anions with one {B(CN)3} unit bonded to the (hetero)arene. An excess of K21 leads to the successive reaction of two or, in the case of perfluoropyridine, even three C–F moieties and the formation of di- and trianions, respectively. Moreover, all of the 11 partially fluorinated benzene derivatives, C6F6−nHn (n = 1–5), generally react with K21 to give new tricyano(phenyl)borate anions with high chemo- and regioselectivity. A decreasing number of fluorine substituents on benzene results in a decrease in the reaction rate. In the cases of partially fluorinated benzenes, the addition of LiCl is advantageous or even necessary to facilitate the reaction. Also, pentafluorobenzenes R–C6F5 (R = –CN, –OMe, –Me, or –CF3) react via C–F/C–B exchange that mostly occurs in the para position and to a lesser extent in the meta or ortho positions. Most of the reactions proceed via an SNAr mechanism. The reaction of 1,4-F2C6H4 with K21 shows that an aryne mechanism has to be considered in some cases as well. In summary, a wealth of new stable tricyano(aryl)borates have been synthesised and fully characterized using multi-NMR spectroscopy and most of them were characterised using single-crystal X-ray diffraction.

Graphical abstract: Borylation of fluorinated arenes using the boron-centred nucleophile B(CN)32− – a unique entry to aryltricyanoborates

Supplementary files

Article information

Article type
Edge Article
Submitted
18 May 2017
Accepted
24 Jun 2017
First published
26 Jun 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 5962-5968

Borylation of fluorinated arenes using the boron-centred nucleophile B(CN)32− – a unique entry to aryltricyanoborates

J. Landmann, P. T. Hennig, N. V. Ignat’ev and M. Finze, Chem. Sci., 2017, 8, 5962 DOI: 10.1039/C7SC02249B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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