88-67-5Relevant articles and documents
Perfluoroalkyl Cobaloximes: Preparation Using Hypervalent Iodine Reagents, Molecular Structures, Thermal and Photochemical Reactivity
Liebing, Phil,Oehler, Florian,Wagner, Mona,Tripet, Pascal F.,Togni, Antonio
, p. 570 - 583 (2018)
Treatment of cobaloximes(II), [Co(Hdmg)2(L)2] (Hdmg = dimethylglyoximate, L = neutral ligand), with perfluoroalkyl iodane reagents leads to the formation of perfluoroalkyl cobaloximes(III), [CoRF(Hdmg)2(L)] (RF = CF3, C2F5, n-C3F7, CF2CF2Ph; L = Py, NH3, MeNH2, PhNH2, MeOH). The synthetic protocol can be significantly simplified to a one-pot procedure starting from cobalt(II) acetate-tetrahydrate. The products have been fully characterized by NMR, IR, and UV/vis spectroscopy as well as single-crystal X-ray diffraction, and the thermal and photochemical reactivity has been studied. According to the Co-L distances in the crystal, the trans influence of the RF- ligands can be rated as C2F5- ≈ n-C3F7- 2CF2Ph- ≈ CF3- 3-. The thermal decomposition of the complexes is different from that of nonfluorinated analogues, probably including perfluoroalkylation of an Hdmg- ligand as the initial step. In the CF3 complexes, the Co-C bond is very resistant against photolysis, but the ligand L is readily exchanged by MeOH upon exposure to blue light. In the complexes with longer RF chains, the Co-C bond is more readily cleaved, and the product distribution depends strongly on the presence of O2. Thus, the alkane RFH is the main product under exclusion of O2, while a fluorinated methyl ester and HF are formed in a methanol solution exposed to air.
Mechanistic Investigation of the Iron-Catalyzed Azidation of Alkyl C(sp3)-H Bonds with Zhdankin’s λ3-Azidoiodane
Chatterjee, Ruchira,Day, Craig S.,Fawcett, Alexander,Hartwig, John F.
supporting information, p. 16184 - 16196 (2021/10/12)
An in-depth study of the mechanism of the azidation of C(sp3)-H bonds with Zhdankin’s λ3-azidoiodane reagent catalyzed by iron(II)(pybox) complexes is reported. Previously, it was shown that tertiary and benzylic C(sp3)-H bonds of a range of complex molecules underwent highly site-selective azidation by reaction with a λ3-azidoiodane reagent and an iron(II)(pybox) catalyst under mild conditions. However, the mechanism of this reaction was unclear. Here, a series of mechanistic experiments are presented that reveal critical features responsible for the high selectivity and broad scope of this reaction. These experiments demonstrate the ability of the λ3-azidoiodane reagent to undergo I-N bond homolysis under mild conditions to form λ2-iodanyl and azidyl radicals that undergo highly site-selective and rate-limiting abstraction of a hydrogen atom from the substrate. The resultant alkyl radical then combines rapidly with a resting state iron(III)-azide complex, which is generated by the reaction of the λ3-azidoiodane with the iron(II)(pybox) complex, to form the C(sp3)-N3bond. This mechanism is supported by the independent synthesis of well-defined iron complexes characterized by cyclic voltammetry, X-ray diffraction, and EPR spectroscopy, and by the reaction of the iron complexes with alkanes and the λ3-azidoiodane. Reaction monitoring and kinetic studies further reveal an unusual effect of the catalyst on the rate of formation of product and consumption of reactants and suggest a blueprint for the development of new processes leading to late-stage functionalization of C(sp3)-H bonds.
Efficiency of lithium cations in hydrolysis reactions of esters in aqueous tetrahydrofuran
Harada, Yumi,Hayashi, Kazuhiko,Ichimaru, Yoshimi,Imai, Masanori,Kojima, Yuki,Maeda, Azusa,Nakayama, Kanae,Sugiura, Kirara
, p. 581 - 594 (2021/06/06)
Lithium cations were observed to accelerate the hydrolysis of esters with hydroxides (KOH, NaOH, LiOH) in a water/tetrahydrofuran (THF) two-phase system. Yields in the hydrolysis of substituted benzoates and aliphatic esters using the various hydroxides were compared, and the effects of the addition of lithium salt were examined. Moreover, it was presumed that a certain amount of LiOH was dissolved in THF by the coordination of THF with lithium cation and hydrolyzed esters even in the THF layer, as in the reaction by a phase-transfer catalyst.
