Solvent Effect on Palladium‐Catalyzed Cross‐Coupling Reactions and Implications on the Active Catalytic Species

Abstract

Suzuki coupling of the bifunctional substrate 1 using [Pd(2)(dba)(3)]/PtBu(3) gives selectivity for C-Cl in nonpolar solvents but for C-OTf in polar solvents. The results of computational and experimental studies suggest that the catalytically active species in polar solvents under conditions employing coordinating additives is inconsistent with monoligated [Pd(PtBu(3))]. Instead, the data are consistent with an anionic palladium complex as the active species.

Reactivity and Stability of Dinuclear Pd(I) Complexes: Studies on the Active Catalytic Species, Insights into Precatalyst Activation and Deactivation, and Application in Highly Selective Cross-Coupling Reactions

“…16 We discovered that employing the identical conditions in polar solvents, such as MeCN, gives rise to a complete selectivity reversal with exclusive transformation of the C−OTf bond. 15 We also demonstrated this selectivity reversal for intermolecular competition experiments and established that it is general in arylboronic acid. 15 Through detailed computational studies, we were able to show that neither electrostatic stabilization nor coordination by the polar solvent accounts for the selectivity reversal (see Figure 3).…”

“…15 We also demonstrated this selectivity reversal for intermolecular competition experiments and established that it is general in arylboronic acid. 15 Through detailed computational studies, we were able to show that neither electrostatic stabilization nor coordination by the polar solvent accounts for the selectivity reversal (see Figure 3). Instead, a different active species is likely the cause of selectivity reversal in polar solvent: the reactivity of Pd 2 (dba) 3 /PtBu 3 in polar solvents was found to be consistent with anionic [Pd(0)PtBu 3 X]¯as active catalytic species if coordinating additives or cross-coupling partners are present in the mixture, leading to preferential C−OTf addition.…”

Synthesis of axially chiral biaryl compounds by asymmetric catalytic reactions with transition metals

“…This is why ligands presenting both a phosphorus and an M a n u s c r i p t [75]. One year later they highlighted the role of the solvent on the selectivity of this reaction, observing that polar solvents stabilized monoligated PdL intermediates, and so oxidative addition across the C-Cl bond [76].…”

Microwave-Promoted Synthesis of 4-Arylpyrimidines by Pd-Catalysed Suzuki–Miyaura Coupling of 4-Pyrimidyl Tosylates in Water

“…The reacting medium may affect the oxidative addition or the transmetalation step 17 or even change the active catalytic species. 18 In the case of the model reaction, formation of compound 3a was favored in polar solvents, such as water, ethanol and N,N-dimethylformamide (DMF), when compared with less polar solvents such as tetrahydrofuran (THF) and toluene. In spite of the poor solubility of the coupling reagents in water, this solvent proved the best medium for the reaction, regardless of the employed heating source.…”