Organotrifluoroborates:  Protected Boronic Acids That Expand the Versatility of the Suzuki Coupling Reaction

Abstract

Organotrifluoroborates represent an alternative to boronic acids, boronate esters, and organoboranes for use in Suzuki-Miyaura and other transition-metal-catalyzed cross-coupling reactions. The trifluoroborate moiety is stable toward numerous reagents that are often problematic for other boron species. Consequently, remote functional groups within the organotrifluoroborates can be manipulated, while retaining the valuable carbon-boron bond.

Development of Efficient Catalytic Arylation of Aldehydes with Thioether-Imidazolinium Carbene Ligands

“…[13][14][15] Due to the advantages of organoboron reagents such as low toxicity, superior stability, and widespread availability, [16][17][18] and the significance of adducts as intermediates for the synthesis of biologically active compounds, [19][20][21] several types of active catalysts have been developed for this kind of reaction, such as palladium, 22) nickel, 23) and copper 24) complexes in addition to recently found effective metal species following our report. [25][26][27][28] However, they did not achieve adequate level performance and high catalyst loading was usually required to obtain sufficient results.…”

“…[46][47][48] Boronic acids often dimerize and trimerize to form boronic acid anhydrides and boroxines, 49) which make difficulties in the direct purification and determination of exact chemical amount. On the other hand, potassium organotrifluoroborates are highly air-and moisture-stable crystalline solids [50][51][52] and more easily prepared, purified, and handled although these compounds are less soluble in organic solvents and require protic solvents for their dissolution.…”

“…On the other hand, potassium organotrifluoroborates are highly air-and moisture-stable crystalline solids [50][51][52] and more easily prepared, purified, and handled although these compounds are less soluble in organic solvents and require protic solvents for their dissolution. [46][47][48] In spite of these advantages, only two kinds of rhodium(I)-phosphine catalysts for the 1,2-addition to aldehydes with potassium organotrifluoroborates have been reported. 53,54) Because the palladium/thioether-imidazolinium chloride system had high tolerance for water, it was expected to be a suitable catalyst system for this type of reagent.…”

Exploration of the reaction of potassium organotrifluoroborates with porphyrins

“…5 This lack of examples is probably due to the fact that cross-coupling reactions using alkyl-metallic compounds have proven problematic as the organopalladium intermediates can undergo β-hydride elimination. 6 However, it has been shown in other areas that the use of potassium organotrifluoroborates instead of boronic acids or esters offers various advantages. 6 The most significant benefit is their higher air stability.…”

“…6 However, it has been shown in other areas that the use of potassium organotrifluoroborates instead of boronic acids or esters offers various advantages. 6 The most significant benefit is their higher air stability. Additionally, there are a number of commercially available potassium organotrifluoroborates that cannot be obtained as the boronic acid or ester analogue due to their instability.…”