New polystyrene-supported stable source of 2-pyridylboron reagent for Suzuki couplings in combinatorial chemistry

A General and Efficient Method for the Suzuki–Miyaura Coupling of 2‐Pyridyl Nucleophiles

“…Further examination of the literature indicated that only a few reports of the Suzuki-Miyaura reaction of 2-pyridyl nucleophiles with aryl halides have appeared, and in these examples, only aryl iodides have been demonstrated as suitable coupling partners. [3,[6][7][8][9][10] The difficulty can be attributed to several factors: 1) Electron-deficient heteroaryl boron derivatives undergo transmetalation at a relatively slow rate, and 2) these reagents rapidly decompose by a protodeboronation pathway. The lack of an efficient method to process this class of nucleophiles led us to develop a technique specifically designed to accomplish this transformation.…”

“…[11] However, the reaction remained sensitive to the nature of the nucleophile and base. For example, the reaction of commercially-available reagents, such as 2-pyridyl boronic acid, [6] pinacol boronate ester, [7] or N-phenyl diethanolamine boronate ester, [8] with 4-n-butylbromobenzene produced low yields of the desired biaryl product ( Table 1, entries 1-3). Similarly, attempts to use organotrifluoroborates resulted in a low conversion of the aryl bromide (Table 1, entry 4).…”

Palladium-Catalyzed 1,1-Difunctionalization of Ethylene

“…Ligand-controlled solutions to some of these issues have been reported recently by the groups of Buchwald, 13 Fu, 14 Plenio, 15 and others. 16 …”

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions

“…Various N -alkyldiethanolamine adducts of arylboronic acids, including methyl 13,14 and phenyl, 15 or N , N -diethanolaminomethyl polystyrene, 16 have been developed to improve stability and ease of use of boronic acids, but most of these derivatives are not crystalline and their use in coupling reactions often requires copper additives. 13,15,16 In contrast, simple diethanolamine (DEA) complexes of boronic acids, or 2,8-dioxa-5-aza-1-bora-bicyclo[3:3:0]octanes (DABO boronates) are air and water stable adducts that allow for easy isolation, characterization, and storage, 17,18,19 DEA is the least expensive auxiliary for stabilizing boronic acids when compared to MIDA, KHF 2 , and pinacol.…”

“…13,15,16 In contrast, simple diethanolamine (DEA) complexes of boronic acids, or 2,8-dioxa-5-aza-1-bora-bicyclo[3:3:0]octanes (DABO boronates) are air and water stable adducts that allow for easy isolation, characterization, and storage, 17,18,19 DEA is the least expensive auxiliary for stabilizing boronic acids when compared to MIDA, KHF 2 , and pinacol. 20 DABO boronates are known to hydrolyze to the boronic acid or ester in aqueous solutions and protic solvents 21 commonly used in coupling reactions, suggesting that they would be viable candidates for Suzuki-Miyaura cross-coupling reactions (Scheme 1).…”