Oxidation of Hydroxyl-Substituted Organotrifluoroborates

Abstract

Potassium- and tetra-n-butylammonium organotrifluoroborates containing hydroxyl groups have been prepared and oxidized using several common oxidants. Aryl-, alkenyl-, and alkyltrifluoroborates containing both primary and secondary hydroxyl groups were oxidized in moderate to excellent yields with complete retention of the trifluoroborate moiety. The utility of these oxidized products was demonstrated in a Suzuki-Miyaura cross-coupling reaction.

Photoredox Catalysis in Nickel-Catalyzed Cross-Coupling

“…Alkyltrifluoroborates with different ring sizes and steric demands were efficiently coupled with aryl-and heteroaryl bromides. In contrast to previous results for similar transformations under traditional Pd-catalyzed conditions [13,16], (±)-2-methylcycloalkyltrifluoroborates afforded the desired products without rearrangement, giving only the racemic, trans-diastereomer (Scheme 6). Importantly, 23 39 alkyltrifluoroborates in which the alkyl group possesses greater s-character have unfavorable redox potentials (because radicals generated from these species are less stable than those with less s-character), thus inhibiting radical formation.…”

“…They are known for undergoing a variety of transformations while keeping the appended carbon-boron bond intact [11][12][13]. Consequently, molecular complexity can be built into various functionalized core reagents, providing more diversity by which targeted molecular platforms can be constructed.…”

Potassium Organotrifluoroborates: New Perspectives in Organic Synthesis

“…87 As many oxidation procedures are conducted in chlorinated solvent, in which potassium salts are insoluble, the TBA organotrifluoroborates were first used. On such substrates TPAP/NMO, Swern and Dess-Martin periodinane oxidations were all successful.…”

“…On the other hand, the potassium salts could be oxidized using 3 equiv of IBX (2-iodoxybenzoic acid) in refluxing acetone. 87 Simple filtration of the IBX byproducts gave a filtrate from which the oxidized products were isolated.…”

ChemInform Abstract: Iterative Cross‐Coupling with MIDA Boronates: Towards a General Strategy for Small‐Molecule Synthesis

“…Trifluoroborate salts represent highly useful surrogates for boronic acidsxxxiv and are compatible with many synthetic reagents xxxv. These features have provided novel access to many new organoborane building blocks.…”