14301-11-2Relevant articles and documents
Enhanced photocatalytic activity of gold nanoparticles driven by supramolecular host-guest chemistry
Padilla, Marc,Peccati, Francesca,Bourdelande, José Luis,Solans-Monfort, Xavier,Guirado, Gonzalo,Sodupe, Mariona,Hernando, Jordi
, p. 2126 - 2129 (2017)
Functionalization of gold nanoparticles with supramolecular hosts allows their plasmon-based photocatalytic activity to be enhanced. This is mainly ascribed to the formation of labile host-guest complexes with the reagent molecules on the metal surface, thus promoting nanoparticle-substrate approximation without interfering with the light-induced catalytic process.
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.
Palladium supported aminobenzamide modified silica coated superparamagnetic iron oxide as an applicable nanocatalyst for Heck cross-coupling reaction
Fatahi, Yousef,Ghaempanah, Aram,Ma?mani, Leila,Mahdavi, Mohammad,Bahadorikhalili, Saeed
, (2021/01/26)
An applicable palladium-based nanocatalyst was constructed through the immobilization of palladium onto 2-aminobenzamide functionalized silica coated superparamagnetic iron oxide magnetic nanoparticles. The nanocatalyst (named as Pd@ABA@SPIONs@SiO2) was characterized by several characterization methods, including scanning electron microscope (SEM), transmission electron microscopy (TEM), vibrating-sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS) analyses. Microscopy results showed that the nanoparticles are spherical in shape with 20–25 nm size. The size of the nanoparticles was confirmed by the DLS method. The superparamagnetic nature of the catalyst was confirmed by the VSM method. The successful functionalization of SPIONs@SiO2 was confirmed by FT-IR spectroscopy. The presence of palladium in the structure of the nanocatalyst was illustrated by XRD and EDS analysis. Also using XPS technique, the oxidation state of palladium in Pd@ABA@SPIONs@SiO2 was determined zero before and after the catalyst was applied in Mizoroki-Heck reaction. Several aryl halides and alkenes were reacted in the presence of the nanocatalyst and formed the corresponding products in high isolated yields. The nanocatalyst showed very good reusability and did not decrease its activity after 10 sequential runs. Density functional theory (DFT) calculation was performed to provide a mechanism for the reaction and confirmed the role of the palladium catalyst in the reaction function.
Stereo-controlledanti-hydromagnesiation of aryl alkynes by magnesium hydrides
Chiba, Shunsuke,Li, Yihang,Ong, Derek Yiren,Pang, Jia Hao,Takita, Ryo,Wang, Bin,Watanabe, Kohei
, p. 5267 - 5272 (2020/06/04)
A concise protocol foranti-hydromagnesiation of aryl alkynes was established using 1?:?1 molar combination of sodium hydride (NaH) and magnesium iodide (MgI2) without the aid of any transition metal catalysts. The resulting alkenylmagnesium intermediates could be trapped with a series of electrophiles, thus providing facile accesses to stereochemically well-defined functionalized alkenes. Mechanistic studies by experimental and theoretical approaches imply that polar hydride addition from magnesium hydride (MgH2) is responsible for the process.
Reductive Difunctionalization of Aryl Alkenes with Sodium Metal and Reduction-Resistant Alkoxy-Substituted Electrophiles
Fukazawa, Mizuki,Nogi, Keisuke,Sasamori, Takahiro,Takahashi, Fumiya,Yorimitsu, Hideki
supporting information, (2020/03/13)
A general method for alkali-metal-promoted reductive difunctionalization of alkenes has been developed by means of reduction-resistant alkoxy-substituted electrophiles. A series of 1,2-diboration and 1,2-dicarbofunctionalization products can be synthesize
Copper-catalysed, diboron-mediated: Cis -dideuterated semihydrogenation of alkynes with heavy water
Han, Xiaowei,Hu, Jiefeng,Chen, Cheng,Yuan, Yu,Shi, Zhuangzhi
supporting information, p. 6922 - 6925 (2019/06/18)
Methods to incorporate deuterium atoms into organic molecules are valuable for the pharmaceutical industry. Here, we found that diboron reagents can efficiently mediate the transfer of two D atoms from heavy water directly onto alkynes through copper-catalysed cis-selective semihydrogenation. Avoiding the use of costly and flammable D2 gas, this safe and practical process can proceed with excellent chemoselectivity and stereoselectivity. Utilizing the present method as the key step, the formal asymmetric total synthesis of d2-deuterium-labeled cis-combretastatin A4 is demonstrated. Mechanistic studies suggest that monoborylation of alkynes is the key step for this semihydrogenation process.
Development of a Palladium-Catalyzed Process for the Synthesis of Z-Alkenes by Sequential Sonogashira–Hydrogenation Reaction
Hancker, S?ren,Neumann, Helfried,Beller, Matthias
supporting information, p. 5253 - 5259 (2018/09/14)
A novel and selective sequential one-pot protocol for the synthesis of Z-alkenes via Sonogashira–semihydrogenation is reported. The efficiency of the methodology is increased by utilizing PdCl2/BuPAd2 as homogeneous catalyst for the Sonogashira coupling and subsequently transforming the transition metal complex into a heterogeneous Pd hydrogenation catalyst. This methodology represents one of the rare examples directly combining homogeneous and heterogeneous catalysis.
Expedient Synthesis of N-Methyl- and N-Alkylamines by Reductive Amination using Reusable Cobalt Oxide Nanoparticles
Senthamarai, Thirusangumurugan,Murugesan, Kathiravan,Natte, Kishore,Kalevaru, Narayana V.,Neumann, Helfried,Kamer, Paul C. J.,Jagadeesh, Rajenahally V.
, p. 1235 - 1240 (2018/02/09)
N-Methyl- and N-alkylamines represent important fine and bulk chemicals that are extensively used in both academic research and industrial production. Notably, these structural motifs are found in a large number of life-science molecules and play vital roles in regulating their activities. Therefore, the development of convenient and cost-effective methods for the synthesis and functionalization of amines by using earth-abundant metal-based catalysts is of scientific interest. In this regard, herein we report an expedient reductive amination process for the selective synthesis of N-methylated and N-alkylated amines by using nitrogen-doped, graphene-activated nanoscale Co3O4-based catalysts. Starting from inexpensive and easily accessible nitroarenes or amines and aqueous formaldehyde or aldehydes in the presence of formic acid, this cost-efficient reductive amination protocol allows the synthesis of various N-methyl- and N-alkylamines, amino acid derivatives, and existing drug molecules.
Z-Stereoselective Aza-Peterson Olefinations with Bis(trimethylsilane) Reagents and Sulfinyl Imines
Das, Manas,OShea, Donal F.
supporting information, p. 336 - 339 (2016/02/03)
Highly stereoselective aza-Peterson olefinations from bench-stable α,α-bis(trimethylsilyl)toluene reagents and N-substituted imines have been achieved using TMSO-/Bu4N+ as Lewis base activator in THF. Remarkably, and for the first time, N-t-butanesulfinyl imines were utilized for the synthesis of Z-stilbenes with excellent selectivities, while N-aryl imines generated E-stilbenes under identical reaction conditions. The protocol proved general for numerous examples with low molecular weight byproducts formed. The origin of the Z-selectivity is proposed to be a result of diastereoselective addition to N-t-butanesulfinyl imines followed by syn-elimination of an in situ formed hypervalent silicate.
Donor/Acceptor-Stabilized 1-Silaketene: Reversible [2+2] Cycloaddition with Pyridine and Evolution by an Olefin Metathesis Reaction
Reyes, Morelia Lopez,Troadec, Thibault,Rodriguez, Ricardo,Baceiredo, Antoine,Saffon-Merceron, Nathalie,Branchadell, Vicen?,Kato, Tsuyoshi
, p. 10247 - 10253 (2016/07/19)
The reaction of silacyclopropylidene 1 with benzaldehyde generates a 1-silaketene complex 2 by a formal atomic silicon insertion into the C=O bond of the aldehyde. The highly reactive 1-silaketene 2 undergoes a reversible [2+2] cycloaddition with pyridine to give sila-β-lactam 3. Of particular interest, in the presence of 4-dimethylaminopyridine (DMAP), 1-silaketene complex 2 evolves through an intramolecular olefin metathesis reaction, generating a new 1-silaketene complex 8 and cis-stilbene. Theoretical studies suggest that the reaction proceeds through the formation of a transient silacyclobutanone, a four-membered-ring intermediate, similar to that proposed by Chauvin and co-workers for the transition-metal-based olefin metathesis.
