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]
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] |
Boronic acids RB(OH)2 react with potassium bifluoride K[HF2] to form trifluoroborate salts K[RBF3].
Organotrifluoroborates are strong nucleophiles and react with electrophiles without transition-metal catalysts.[6]
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]