Cobalt‐Catalyzed Electrophilic Amination of Aryl‐ and Heteroarylzinc Pivalates with N‐Hydroxylamine Benzoates

Aryl‐ and heteroarylzinc pivalates can be aminated with O‐benzoylhydroxylamines at 25 °C within 2–4 h in the presence of 2.5–5.0 % CoCl₂?2 LiCl to furnish the corresponding tertiary arylated or heteroarylated amines in good yields. This electrophilic amination also provides access to diarylamines and aryl(heteroaryl)amines. A new tuberculosis drug candidate (Q203) was prepared in six steps and 56 % overall yield by using this cobalt‐catalyzed amination as the key step.     

The kinetics and main pathways for the liquid-phase oxidation of cyclohexene by air in the presence of cobalt,chromium, iron,and nickel µ<Subscript>3</Subscript>-oxotrimetallohexapivalates

It was found that during the liquid-phase oxidation of cyclohexene (CH) by air (323–343 K) in the presence of a series of homo-and heteronuclear μ ₃-oxotrimetallohexapivalates with a M₂M′O (M, M′ = Co, Cr, Fe, Ni) core insignificant amounts of the corresponding epoxide are formed, and 3-hydroperoxy-2-cyclohexene (HP), 3-hydroxy-2-cyclohexene (CHol), and 2-cyclohexen-3-one (CHone) accumulate in the oxidate. It is suggested that CHone and CHol are “dead-end” products from the oxidation of CH under the investigated conditions while the HP is a unique “intermediate-damper” that gives rise to the realization of alternative paths (catalytic cycles) for the formation of these products. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 85–90, March–April, 2007.     

Polynuclear mixed-ligand NiII complexes containing pivalate and hexafluoroacetylacetonate ligands: a new single-molecule magnet

The reaction of NiCl₂ with excess potassium pivalate (KPiv) in ethanol affords the chainpolymeric compound KNi₄(Piv)₇(OH)₂(EtOH)₆. In the solid compound, the tetranuclear nickel fragments alternate with potassium atoms. The use of KNi₄(Piv)₇(OH)₂(EtOH)₆ in the reaction with Ni(hfac)₂ (hfac is the hexafluoroacetylacetonate anion) gave the first polynuclear mixed-ligand complexes [K₂Ni₆(Piv)₇(hfac)₃(OH)₄(HPiv)₂(Me₂CO)₂]·1.5C₇H₁₆, [Ni₆(Piv)₄(hfac)₄(OH)₄(Me₂CO)₄], [K₂Ni₈(Piv)₈(hfac)₄(OH)₆(H₂O)₂(Me₂CO)₆], [Ni₈(Piv)₁₀(hfac)₂(OH)₂(MeO)₂(MeOH)₂(HPiv)₂]·C₆H₁₄, and [Ni₁₆(Piv)₁₀(hfac)₆(OH)₁₀(MeO)₆(MeOH)₈(H₂O)₆]·C₆H₁₄ containing both Piv and hfac as the anionic ligands. The molecular and crystal structures of all these compounds were established, and their magnetic properties were studied. All solids containing simultaneously Piv and hfac ligands tend to undergo ferromagnetic ordering with decreasing temperature. The solid [Ni₈(Piv)₁₀(hfac)₂(OH)₂(MeO)₂(MeOH)₂(HPiv)₂]·C₆H₁₄ undergoes cooperative magnetic ordering below T _c (2.5 K). Dedicated to the 90th anniversary of the L. Ya. Karpov Institute of Physical Chemistry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1175–1182, June, 2008.     

Preparation of Solid Polyfunctional Alkynylzinc Pivalates with Enhanced Air and Moisture Stability for Organic Synthesis

We report the preparation of solid and air-stable polyfunctionalized alkynylzinc pivalates from the corresponding alkynes using TMPZnOPiv (TMP=2,2,6,6-tetramethylpiperidyl) as base. These organozinc pivalates are obtained as powders under mild conditions in excellent yields and can be manipulated in air for several hours without significant decomposition. These zinc reagents show an excellent reactivity in various carbon–carbon bond- forming reactions and 1,3-dipolar cycloadditions. An alkynylzinc pivalate has been used to prepare a carboxyamidotriazole with potential antineoplastic activity in eight steps and 38 % overall yield.     

Theoretical prediction on the synthesis of 2,3‐dihydropyridines through Co(III)‐catalysed reaction of unsaturated oximes with alkenes

Cobalt‐based catalysts can replace the homologous group‐9 rhodium‐based ones. Herein, we used density functional theory (DFT) calculations to predict the synthesis of 2,3‐dihydropyridines using α,β‐unsaturated oxime pivalates and alkenes catalysed by [Cp*CoOAc]⁺ instead of [Cp*RhOAc]⁺. The catalytic cycle involves reversible acetate‐assisted metalation‐deprotonation, migratory insertion of alkenes, and reductive elimination/N‐O cleavage. The migratory insertion of alkenes was determined to be the rate‐determining step, and the reaction is irreversible due to the strongly exergonic reductive elimination/N? O cleavage. When using the CF₃‐substituted Cp*Co(III) catalyst, the apparent activation energy indicates that the title reaction can proceed at higher temperatures. Electron‐withdrawing substituent groups on Cp* facilitate the reaction. In contrast, substituting phenyl with the electron‐deficient p‐CF₃‐phenyl at the 2‐position of α,β‐unsaturated oxime pivalate hinders the reaction, and so does the use of polarized alkenes with electron‐withdrawing substituent groups     

Influence of the nature of organic components in dinuclear copper(II) pivalates on the composition of thermal decomposition products

Tetrabridged dinuclear complexes ((2-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (2·С₆Н₆) and ((3-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (3) and the cocrystallization product ((4-NMe₂)C₅H₄N)₂Cu(η²–OOCCMe₃)₂·2((4-NMe₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (4) were synthesized by the reaction of the polymer [Cu(OOCCMe₃)₂]_n (1) with aminopyridine ligands (L) of different nature (Cu: L = 1:1) in С₆Н₆. The solid-state thermal decomposition of these compounds was studied by differential scanning calorimetry and thermogravimetry, and their electrochemical behavior was investigated by cyclic voltammetry. All newly synthesized complexes were studied by X-ray diffraction, the magnetic properties of the complexes were investigated, and ESR measurements were performed.