Organotrifluoroborates are organoboron compounds that contain an anion with the general formula [RBF3]−. They can be thought of as protected boronic acids, or as adducts of carbanions and boron trifluoride. Organotrifluoroborates are tolerant of air and moisture and are easy to handle and purify. They are often used in organic synthesis as alternatives to boronic acids (RB(OH)2), boronate esters (RB(OR′)2), and organoboranes (R3B), particularly for Suzuki-Miyaura coupling.
Structure
| thermal ellipsoid model of [PhBF3]−, as foundin the crystal structure of K[PhBF3]5 | space-filling packing diagram ofthe crystal structure of K[PhBF3]6 |
Synthesis
See also: Organoboron chemistry § Borates
Boronic acids RB(OH)2 react with potassium bifluoride K[HF2] to form trifluoroborate salts K[RBF3].
Reactivity
Organotrifluoroborates are strong nucleophiles and react with electrophiles without transition-metal catalysts.7
Mechanism
The mechanism of organotrifluoroborate-based Suzuki-Miyaura coupling reactions has recently been investigated in detail. The organotrifluoroborate hydrolyses to the corresponding boronic acid in situ, so a boronic acid can be used in place of an organotrifluoroborate, as long as it is added slowly and carefully.89
References
"Alfa Aesar – Product Flyers & Technical Reviews – Organotrifluoroborates" (PDF). http://www.alfa.com/en/docs/Organotrifluoroborates.pdf ↩
"Sigma-Aldrich – Chemical Synthesis – Technology Spotlights – Organotrifluoroborates". 2012-09-09. Archived from the original on 2012-09-09. https://archive.today/20120909074142/http://www.sigmaaldrich.com/chemistry/chemical-synthesis/technology-spotlights/organotrifluoroborates.html ↩
Darses, Sylvain; Genet, Jean-Pierre (2008). "Potassium Organotrifluoroborates: New Perspectives in Organic Synthesis". Chemical Reviews. 108 (1): 288–325. doi:10.1021/cr0509758. PMID 18095714. /wiki/Chemical_Reviews ↩
Molander, Gary A.; Ellis, Noel (2007). "Organotrifluoroborates: Protected Boronic Acids That Expand the Versatility of the Suzuki Coupling Reaction". Accounts of Chemical Research. 40 (4): 275–286. doi:10.1021/ar050199q. PMID 17256882. /wiki/Accounts_of_Chemical_Research ↩
Conole, G.; Clough, A.; Whiting, A. (1995). "Potassium Trifluorophenylborate". Acta Crystallogr. C. 51 (6): 1056–1059. doi:10.1107/S0108270194014198. /wiki/Acta_Crystallographica ↩
Conole, G.; Clough, A.; Whiting, A. (1995). "Potassium Trifluorophenylborate". Acta Crystallogr. C. 51 (6): 1056–1059. doi:10.1107/S0108270194014198. /wiki/Acta_Crystallographica ↩
Berionni, G.; Maji, B.; Knochel, P.; Mayr, H. (2012). "Nucleophilicity parameters for designing transition metal-free C–C bond forming reactions of organoboron compounds". Chemical Science. 3 (3): 878–882. doi:10.1039/C2SC00883A. /wiki/Chemical_Science_(journal) ↩
Butters, M.; Harvey, J. N.; Jover, J.; Lennox, A. J. J.; Lloyd-Jones, G. C.; Murray, P. M. (2010). "Aryl Trifluoroborates in Suzuki-Miyaura Coupling: The Roles of Endogenous Aryl Boronic Acid and Fluoride". Angew. Chem. Int. Ed. 49 (30): 5156–60. doi:10.1002/anie.201001522. PMID 20544767. /wiki/Angewandte_Chemie ↩
"Mechanism Of Suzuki-Miyaura Coupling Revealed". Chemical & Engineering News. Retrieved 2010-06-27. http://pubs.acs.org/isubscribe/journals/cen/88/i26/html/8826scic6.html ↩