501374-30-7Relevant articles and documents
Ni-Catalyzed Borylation of Aryl Sulfoxides
Huang, Mingming,Wu, Zhu,Krebs, Johannes,Friedrich, Alexandra,Luo, Xiaoling,Westcott, Stephen A.,Radius, Udo,Marder, Todd B.
, p. 8149 - 8158 (2021/05/10)
A nickel/N-heterocyclic carbene (NHC) catalytic system has been developed for the borylation of aryl sulfoxides with B2(neop)2 (neop=neopentyl glycolato). A wide range of aryl sulfoxides with different electronic and steric properties were converted into the corresponding arylboronic esters in good yields. The regioselective borylation of unsymmetric diaryl sulfoxides was also feasible leading to borylation of the sterically less encumbered aryl substituent. Competition experiments demonstrated that an electron-deficient aryl moiety reacts preferentially. The origin of the selectivity in the Ni-catalyzed borylation of electronically biased unsymmetrical diaryl sulfoxide lies in the oxidative addition step of the catalytic cycle, as oxidative addition of methoxyphenyl 4-(trifluoromethyl)phenyl sulfoxide to the Ni(0) complex occurs selectively to give the structurally characterized complex trans-[Ni(ICy)2(4-CF3-C6H4){(SO)-4-MeO-C6H4}] 4. For complex 5, the isomer trans-[Ni(ICy)2(C6H5)(OSC6H5)] 5-I was structurally characterized in which the phenyl sulfinyl ligand is bound via the oxygen atom to nickel. In solution, the complex trans-[Ni(ICy)2(C6H5)(OSC6H5)] 5-I is in equilibrium with the S-bonded isomer trans-[Ni(ICy)2(C6H5)(SOC6H5)] 5, as shown by NMR spectroscopy. DFT calculations reveal that these isomers are separated by a mere 0.3 kJ/mol (M06/def2-TZVP-level of theory) and connected via a transition state trans-[Ni(ICy)2(C6H5)(η2-{SO}-C6H5)], which lies only 10.8 kcal/mol above 5.
Cobalt-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross Coupling
Ludwig, Jacob R.,Simmons, Eric M.,Wisniewski, Steven R.,Chirik, Paul J.
supporting information, (2020/11/02)
A cobalt-catalyzed method for the C(sp2)-C(sp3) Suzuki-Miyaura cross coupling of aryl boronic esters and alkyl bromides is described. Cobalt-ligand combinations were assayed with high-throughput experimentation, and cobalt(II) sources with trans-N,N′-dimethylcyclohexane-1,2-diamine (DMCyDA, L1) produced optimal yield and selectivity. The scope of this transformation encompassed steric and electronic diversity on the aryl boronate nucleophile as well as various levels of branching and synthetically valuable functionality on the electrophile. Radical trap experiments support the formation of electrophile-derived radicals during catalysis.
Small Phosphine Ligands Enable Selective Oxidative Addition of Ar-O over Ar-Cl Bonds at Nickel(0)
Entz, Emily D.,Hooker, Leidy V.,Neufeldt, Sharon R.,Russell, John E. A.
supporting information, p. 15454 - 15463 (2020/10/18)
Current methods for Suzuki-Miyaura couplings of nontriflate phenol derivatives are limited by their intolerance of halides including aryl chlorides. This is because Ni(0) and Pd(0) often undergo oxidative addition of organohalides at a similar or faster rate than most Ar-O bonds. DFT and stoichiometric oxidative addition studies demonstrate that small phosphines, in particular PMe3, are unique in promoting preferential reaction of Ni(0) with aryl tosylates and other C-O bonds in the presence of aryl chlorides. This selectivity was exploited in the first Ni-catalyzed C-O-selective Suzuki-Miyaura coupling of chlorinated phenol derivatives where the oxygen-containing leaving group is not a fluorinated sulfonate such as triflate. Computational studies suggest that the origin of divergent selectivity between PMe3 and other phosphines differs from prior examples of ligand-controlled chemodivergent cross-couplings. PMe3 effects selective reaction at tosylate due to both electronic and steric factors. A close interaction between nickel and a sulfonyl oxygen of tosylate during oxidative addition is critical to the observed selectivity.
