Organotrifluoroborate Explained

Organotrifluoroborates are organoboron compounds that contain an anion with the general formula [RBF<sub>3</sub>]−. They can be thought of as protected boronic acids, or as adducts of carbanions and boron trifluoride. Organotrifluoroborates are tolerant of air and moisture[1] and are easy to handle and purify.[2] 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.[3] [4]

Synthesis

Boronic acids RB(OH)2 react with potassium bifluoride K[HF<sub>2</sub>] to form trifluoroborate salts K[RBF<sub>3</sub>].

Reactivity

Organotrifluoroborates are strong nucleophiles and react with electrophiles without transition-metal catalysts.[6]

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.[7] [8]

Notes and References

  1. Web site: Alfa Aesar – Product Flyers & Technical Reviews – Organotrifluoroborates.
  2. Web site: Sigma-Aldrich – Chemical Synthesis – Technology Spotlights – Organotrifluoroborates . 2012-09-09 . https://archive.today/20120909074142/http://www.sigmaaldrich.com/chemistry/chemical-synthesis/technology-spotlights/organotrifluoroborates.html . 2012-09-09.
  3. . 108 . 2008 . 1. 288–325 . Potassium Organotrifluoroborates: New Perspectives in Organic Synthesis . Sylvain . Darses . Jean-Pierre . Genet . 10.1021/cr0509758 . 18095714.
  4. . 40 . 2007 . 4. 275–286 . Organotrifluoroborates: Protected Boronic Acids That Expand the Versatility of the Suzuki Coupling Reaction . Gary A. . Molander . Noel . Ellis . 10.1021/ar050199q . 17256882.
  5. G. . Conole . A. . Clough . A. . Whiting . Potassium Trifluorophenylborate . . 1995 . 51 . 1056–1059 . 10.1107/S0108270194014198 . 6 .
  6. G. . Berionni . B. . Maji . P. . Knochel . H. . Mayr . . 3 . 3 . Nucleophilicity parameters for designing transition metal-free C–C bond forming reactions of organoboron compounds . 878–882 . 2012 . 10.1039/C2SC00883A .
  7. M. . Butters . J. N. . Harvey . J. . Jover . A. J. J. . Lennox . G. C. . Lloyd-Jones . P. M. . Murray . . 49 . Aryl Trifluoroborates in Suzuki-Miyaura Coupling: The Roles of Endogenous Aryl Boronic Acid and Fluoride . 5156–60 . 2010 . 10.1002/anie.201001522 . 20544767 . 30.
  8. Web site: Mechanism Of Suzuki-Miyaura Coupling Revealed . . 2010-06-27.

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