1780-19-4 Alternative Strategy to Obtain Artificial Imine Reductase by Exploiting Vancomycin/D-Ala-D-Ala Interactions with an Iridium Metal Complex

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Based on the supramolecular interaction between vancomycin (Van), an antibiotic glycopeptide, and D-Ala-D-Ala (DADA) dipeptides, a novel class of artificial metalloenzymes was synthesized and characterized. The presence of an iridium(III) ligand at the N-terminus of DADA allowed the use of the metalloenzyme as a catalyst in the asymmetric transfer hydrogenation of cyclic imines. In particular, the type of link between DADA and the metal-chelating moiety was found to be fundamental for inducing asymmetry in the reaction outcome, as highlighted by both computational studies and catalytic results. Using the [IrCp*(m-I)Cl]Cl Van complex in 0.1 M CH3COONa buffer at pH 5, a significant 70% (S) e.e. was obtained in the reduction of quinaldine B. https://www.lookchem.com/CASDataBase_1780-19-4.htm

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100-64-1 On the Oxidation of Hydroxylamines with o -Iodoxybenzoic Acid (IBX)

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o -Iodoxybenzoic acid (IBX) is confirmed as a powerful tool for the oxidation of hydroxylamines. The synthetic route is demonstrated as efficient and user friendly, and is exploited on various carbohydrate-derived N,N-disubstituted hydroxylamines (cyclic, acyclic, and functionalized ones), affording the corresponding nitrones in good yields and regioselectivity. N-Monosubstituted hydroxylamines revealed an interesting divergent behavior depending on the reaction conditions. While IBX oxidation in dimethyl sulfoxide at 45 °C furnished oximes as reported, the oxidation in dichloromethane at room temperature afforded efficiently the unusual corresponding nitroso dimers. https://www.lookchem.com/CASDataBase_100-64-1.htm
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75-01-4 Nickel(I) Octaethylisobacteriochlorin Anion. An Exceptional Nucleophile. Reduction and Coupling of Alkyl Halides by Anionic and Radical Processes. A Model for Factor F-430

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Nickel(I)octaethylisobacteriochlorin anion (Ni(I)OEiBC - ) reacts extremely rapidly with aliphatic halides and methyl tosylate in homogeneous DMF solution.The reactivity sequence, CH3 > primary > secondary tertiary, and the rate law accord with an S N 2-like process for the carbon-halogen bond scission.However, the main products of the reactions derive from free radicals.The rate for methyl chloride is 2000 times faster than the corresponding reaction with the super nucleophile Co(I)B12 s -1 and the rate constant for isopropyl bromide is 350 times greater than that observed with CpFe(CO)2 - .The results indicate NiOEiBC - is the fastest nucleophile on record.Studies of the influence of solvent and reactant deuteration and the influence of anion and radical scavengers upon the product distribution suggest the intermediacy of at least one and possibly two nickel alkyls of fleeting lifetime.A novel explanation for the unusual speed of these reactions is put forward.It entails the...
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100-40-3 ?-Arene Complexes of Nickel(II). Synthesis (from Metal Atoms) of (?-Arene)bis(pentafluorophenyl)nickel(II). Properties, ?-Arene Lability, and Chemistry

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A new series of transition-metal-?-arene complexes has been prepared by a metal atom synthetic method.The deposition of Ni vapor, C6F5Br, and arenes has prodused high yields of (C6F5)2Ni-?-arene complexes.A variety of ?-arene ligands are η 6 bound by the (C6F5)2Ni moiety, resulting in soluble highly labile materials, where the ?-arene ligand is exchangeble at room temperature.These complexes have not been isolable when ?-bonding ligands other then C6F5 have been employed.The formation of the ?-toluene complex proceeds through a pseudostable C6F5NiBr species that can be trapped at -80 deg C with R3P but decomposes by reductive elimination of CF5-CF5 in the absence of R3P or electron-rich arenes.It is likely that C6F5NiBr-?-arene is formed initially, which then disproportionates to (C6F5)2Ni-?-arene and NiBr2.Due to the high lability of the ?-arene ligand, these complexes possess a rich chemistry.Displacement of the ?-arene ligand can bee carried out cleanly and in high yield by P(Et)3,...
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