Organotrifluoroborate

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File:Organotrifluoroborate-anion-general-2D.png
General structural formula of an organotrifluoroborate anion

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[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]

Structure

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thermal ellipsoid model of [PhBF3], as found
in the crystal structure of K[PhBF3][5]
space-filling packing diagram of
the crystal structure of K[PhBF3][5]

Synthesis

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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.[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]

References

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