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41.
Dr. Yutaka Ishida Sui Hasegawa Prof. Dr. Hiroyuki Kawaguchi 《Angewandte Chemie (International ed. in English)》2023,62(31):e202304700
Here we show that a tridentate bis(aryloxide)anilide-ligated titanium/potassium scaffold promotes functionalization of coordinated N2 with CO2 and CS2 through formation of N−C bonds. Treatment of a naphthalene complex with N2 gave an end-on bridging dinitrogen complex featuring a [Ti2K2N2] core. The dinitrogen complex underwent insertion of CO2 into each Ti−NN bond to afford an N,N′-dicarboxylated hydrazido complex. Stepwise nitrogen-carbon bond formation at coordinated N2 proceeded to afford an unsymmetric hydrazido complex upon sequentially treating the dinitrogen complex with CS2 and CO2. Addition of Me3SiCl to the dicarboxylated hydrazido complex resulted in partial silylation of the carboxylate groups but did not lead to removal of the functionalized N2 unit from the metal centers. However, reduction of the dicarboxylated hydrazido complex with potassium naphthalenide afforded an oxo-bridged dinuclear complex along with release of free potassium cyanate. 相似文献
42.
Tim van Lingen Dr. Valentina Bragoni Dr. Marco Dyga Dr. Benjamin Exner Daniel Schick Dr. Christoph Held Prof. Dr. Gabriele Sadowski Prof. Dr. Lukas J. Gooßen 《Angewandte Chemie (International ed. in English)》2023,62(27):e202303882
The inherent formation of salt waste in C−H carboxylations is a key obstacle precluding the utilization of CO2 as C1 building block in the industrial synthesis of base chemicals. This challenge is addressed in a circular process for the production of the C4 base chemical dimethyl succinate from CO2 and acetylene. At moderate CO2 pressures, acetylene is doubly carboxylated in the presence of cesium carbonate. Hydrogenation of the C−C triple bond stabilizes the product against decarboxylation. By increasing the CO2 pressure to 70 bar, the medium is reversibly acidified, allowing an esterification of the succinate salt with methanol. The cesium base and the hydrogenation catalyst are regenerated and can be reused. This provides the proof of concept for a salt-free route to C4 chemicals from biogas (CH4/CO2). The origin of this reversible acidity switch and the critical roles of the cesium base and the NMP/MeOH solvents were elucidated by thermodynamic modeling. 相似文献
43.
Peng-Zi Wang Prof. Dr. Wen-Jing Xiao Prof. Dr. Jia-Rong Chen 《Angewandte Chemie (International ed. in English)》2023,62(21):e202302227
Catalytic and switchable C−H functionalization of N-heteroarenes under easily tunable conditions is a robust but challenging tool for the construction of biologically relevant compounds. Recently, a general electrochemical strategy has been developed for the direct C−H carboxylation of N-heteroarenes with CO2, and by simply choosing different types of cell setups, carboxylated products are furnished with excellent and tunable site selectivity. This study also paves the way for regulating the reactivity modes in electrochemical synthesis. 相似文献
44.
Lin Chen Quan Qu Chuan-Kun Ran Wei Wang Dr. Wei Zhang Yi He Dr. Li-Li Liao Prof. Dr. Jian-Heng Ye Prof. Dr. Da-Gang Yu 《Angewandte Chemie (International ed. in English)》2023,62(11):e202217918
Visible-light photocatalytic carboxylation with CO2 is highly important. However, it still remains challenging for reluctant substrates with low reduction potentials. Herein, we report a novel photocatalytic carboxylation of C−N bonds in cyclic amines with CO2 via consecutive photo-induced electron transfer (ConPET). It is also the first photocatalytic reductive ring-opening reaction of azetidines, pyrrolidines and piperidines. This strategy is practical to transform a variety of easily available cyclic amines to valuable β-, γ-, δ- and ϵ-amino acids in moderate-to-excellent yields. Moreover, the method also features mild and transition-metal-free conditions, high selectivity, good functional-group tolerance, facile scalability and product derivations. Mechanistic studies indicate that the ConPET might be the key to generating highly reactive photocatalysts, which enable the reductive activation of cyclic amines to generate carbon radicals and carbanions as the key intermediates. 相似文献
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