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Jonghoon Choi Yunho Lee 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7012-7016
A three‐coordinate low‐spin cobalt(I) complex generated using a pincer ligand is presented. Since an empty orbital is sterically exposed at the site trans to the N donor of an acridane moiety, the cobalt(I) center accepts the coordination of various donors such as H2 and PhSiH3 revealing σ‐complex formation. At this low‐spin cobalt(I) site, homolysis of H–H and Si?H bonds preferentially occurs via bimolecular hydrogen atom transfer instead of two‐electron oxidative addition. When the resulting CoII–H species was exposed to N2, H2 evolution readily occurs at ambient conditions. These results suggest single‐electron processes are favored at the structurally rigidified cobalt center. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(13):3564-3569
Metal‐superoxo species are involved in a variety of enzymatic oxidation reactions, and multi‐electron oxidation of substrates is frequently observed in those enzymatic reactions. A CrIII‐superoxo complex, [CrIII(O2)(TMC)(Cl)]+ ( 1 ; TMC=1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane), is described that acts as a novel three‐electron oxidant in the oxidation of dihydronicotinamide adenine dinucleotide (NADH) analogues. In the reactions of 1 with NADH analogues, a CrIV‐oxo complex, [CrIV(O)(TMC)(Cl)]+ ( 2 ), is formed by a heterolytic O−O bond cleavage of a putative CrII‐hydroperoxo complex, [CrII(OOH)(TMC)(Cl)], which is generated by hydride transfer from NADH analogues to 1 . The comparison of the reactivity of NADH analogues with 1 and p ‐chloranil (Cl4Q) indicates that oxidation of NADH analogues by 1 proceeds by proton‐coupled electron transfer with a very large tunneling effect (for example, with a kinetic isotope effect of 470 at 233 K), followed by rapid electron transfer. 相似文献
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Wan‐Lei Yu Yong‐Chun Luo Lei Yan Dan Liu Zhu‐Yin Wang Peng‐Fei Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11057-11061
A synergistic catalytic method combining photoredox catalysis, hydrogen‐atom transfer, and proton‐reduction catalysis for the dehydrogenative silylation of alkenes was developed. With this approach, a highly concise route to substituted allylsilanes has been achieved under very mild reaction conditions without using oxidants. This transformation features good to excellent yields, operational simplicity, and high atom economy. Based on control experiments, a possible reaction mechanism is proposed. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(50):16195-16199
Dicobalt complexes supported by flexible macrocyclic ligands were used to target the generation of the bridging nitrido species [(n PDI2)Co2(μ‐N)(PMe3)2]3+ (PDI=2,6‐pyridyldiimine; n =2, 3, corresponding to the number of catenated methylene units between imino nitrogen atoms). Depending on the size of the macrocycle and the reaction conditions (solution versus solid‐state), the thermolysis of azide precursors yielded bridging phosphinimido [(2PDI2)Co2(μ‐NPMe3)(PMe3)2]3+, amido [(n PDI2)Co2(μ‐NH2)(PMe3)2]3+ (n =2, 3), and C−H amination [(3PDI2*‐μ‐NH)Co2(PMe3)2]3+ products. All results are consistent with the initial formation of [(n PDI2)Co2(μ‐N)(PMe3)2]3+, followed by 1) PMe3 attack on the nitride, 2) net hydrogen‐atom transfer to form N−H bonds, or 3) C−H amination of the alkyl linker of the n PDI2 ligand. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(19):5467-5471
The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation method for the selective functionalization of alcohol α‐hydroxy C−H bonds. This approach employs zinc‐mediated alcohol deprotonation to activate α‐hydroxy C−H bonds while simultaneously suppressing C−O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn‐based Lewis acids also deactivates other hydridic bonds such as α‐amino and α‐oxy C−H bonds. This approach facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3‐step synthesis of the drug Prozac exemplifies the utility of this new method. 相似文献