2170-06-1Relevant articles and documents
Reactions of in situ generated (η2-phenyltrimethylsilylacetylene)zirconocene
Erker, Gerhard,Zwettler, Roland
, p. 179 - 188 (1991)
The five-membered metallacycle (1, R1 = SiMe3, R2 = Ph) is a suitable starting material for the in situ generation of the reactive (η2-phenyltrimethylsilylethyne)zirconocene (3).Thus, thermolysis of 1 (70 deg C) with trimethylphosphane gives Cp2Zr(Me3SiCCPh)(PMe3) (8) and free Me3SiCCPh (4).Subsequent reaction of 8 with acetophenone produces (9, R1 = SiMe3, R2 = Ph).Thermolysis of 1 in the presence of CpW(CO)3H also results in the liberation of one equivalent of 4.The reactive intermediate 3 is protonated to giveCp2Zr(CR1=CHR2)(μ-OC)W(CO)2Cp (12, R1 = SiMe3, R2 = Ph).Treatment of 1 with in acetonitrile gives the cationic (13a: R1 = SiMe3, R2 = Ph) and its regioisomer 13b (R1 and R2 exchanged).There is evidence that the complexes 13 are formed by acetonitrile addition to thermally-generated 3 to give , which is then subsequently protonated at the basic ring nitrogen.These reactions show that a readily available metallacyclopentadiene system can be used as a convenient synthetic equivalent of a very reactive (η2-alkyne)metallocene complex by thermally induced equilibration in the presence of suitable trapping reagents.
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Zakharkin et al.
, p. 881,886 (1965)
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Bimetallic nano-Pd/PdO/Cu system as a highly effective catalyst for the Sonogashira reaction
Korzec, Mateusz,Bartczak, Piotr,Niemczyk, Anna,Szade, Jacek,Kapkowski, Maciej,Zenderowska, Paulina,Balin, Katarzyna,Lelatko, Jozef,Polanski, Jaroslaw
, p. 1 - 8 (2014)
A copper-supported nanopalladium catalyst obtained by an innovative method of nanoparticle transfer from the intermediate carrier SiO2 to the target Cu carrier was a highly efficient and selective catalyst, giving as much as quantitative conver
A practical and efficient method for late-stage deuteration of terminal alkynes with silver salt as catalyst
Wu, Ding-Chuan,Bai, Jing-Wen,Guo, Lei,Hu, Guang-Qi,Liu, Kai-Hui,Sheng, Fei-Fei,Zhang, Hong-Hai,Sun, Zheng-Yi,Shen, Kang,Liu, Xiang
, (2021)
A practical and efficient H/D exchange method for selective deuteration of terminal alkynes was disclosed. The reaction was simply performed with CF3COOAg as catalyst at room temperature, affording products with high level of deuterium incorporation. The excellent site-selectivity and promising functional group tolerance of this protocol enabled deuteration of pharmaceuticals and nature product derivatives.
Formation and ligand-based reductive chemistry of bridged bis-alkylidene scandium(III) complexes
Ma, Wangyang,Yu, Chao,Chi, Yue,Chen, Tianyang,Wang, Lianjun,Yin, Jianhao,Wei, Baosheng,Xu, Ling,Zhang, Wen-Xiong,Xi, Zhenfeng
, p. 6852 - 6856 (2017)
The chemistry of rare-earth carbene and alkylidene complexes including their synthesis, structure and reaction is a challenging issue because of their high reactivity (or instability) and the lack of synthetic methods. In this work, we report the first synthesis of the bridged bis-alkylidene complexes which feature a 2-butene-1,1,4,4-tetraanion and four Sc-C(sp3) bonds by the reaction of 1,4-dilithio-1,3-butadienes with ScCl3. This reaction proceeds via two key intermediates: an isolable scandacyclopentadiene and a proposed scandacyclopropene. The scandacyclopentadiene undergoes β,β′-C-C bond cleavage to generate the scandacyclopropene, which then dimerizes to afford the bridged bis-alkylidene complex via a cooperative double metathesis reaction. Reaction chemistry study of the bridged bis-alkylidene complex reveals their ligand-based reduction reactivity towards different oxidants such as hexachloroethane, disulfide and cyclooctatetraene.
Site-Selective Csp3-Csp/Csp3-Csp2Cross-Coupling Reactions Using Frustrated Lewis Pairs
Dasgupta, Ayan,Stefkova, Katarina,Babaahmadi, Rasool,Yates, Brian F.,Buurma, Niklaas J.,Ariafard, Alireza,Richards, Emma,Melen, Rebecca L.
supporting information, p. 4451 - 4464 (2021/04/07)
The donor-acceptor ability of frustrated Lewis pairs (FLPs) has led to widespread applications in organic synthesis. Single electron transfer from a donor Lewis base to an acceptor Lewis acid can generate a frustrated radical pair (FRP) depending on the s
An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
Huang, Zhidao,Wang, Yulei,Leng, Xuebing,Huang, Zheng
supporting information, p. 4824 - 4836 (2021/04/07)
The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.