China
Africa
Explore chapters and articles related to this topic
Catalytic Reactions on Solid Surfaces
Published in Qingmin Ji, Harald Fuchs, Soft Matters for Catalysts, 2019
Huihui Kong, Xinbang Liu, Harald Fuchs
Another possibility for C–H activation of terminal alkyne is forming organometallic covalent bonds as demonstrated by Liu et al. in 2015 [30]. Surface reactions of 2,5-diethynyl-1,4-bis(phenylethynyl)-benzene on Ag(111), Ag(110), and Ag(100) were systematically explored by using STM. On Ag(111), Glaser coupling reaction was dominant and 1D molecular wires are generated. On Ag(110) and Ag(100), however, the terminal alkynes radicals covalently bind to surface metal atoms rather than other terminal alkyne radicals, which further results in the formation of one-dimensional organometallic chains, as shown in Fig. 7.12a–d. Detailed analyses revealed that the different reaction products should be attributed to the matching degree between the periodicities of the produced molecular wires and the substrate lattice structures. In addition, Sun et al. for the first time achieved the on-surface synthesis of metalated carbyne chains by zehydrogenative coupling of ethyne molecules and copper atoms on a Cu(110) surface under ultrahigh-vacuum conditions [31]. The length of the fabricated metalated carbyne chains was found capable of extending to the submicron scale (with the longest ones up to ∼120 nm).
A new Cu3Al-layered double hydroxide heterogeneous catalyst for azide-alkyne [3 + 2] cycloaddition reaction in water
Published in Journal of Coordination Chemistry, 2022
Noura Aflak, Lekbira EL Mersly, Hicham Ben EL Ayouchia, Salah Rafqah, Hafid Anane, Miguel Julve, Salah-Eddine Stiriba
The possible mechanism for the formation of 1,4-disubstituted-1,2,3-triazoles by using the as-prepared Cu3Al-LDH catalyst is shown in Scheme 2. Based on previous studies [15,16, 33] and experimental results, the first step is the reduction of the six-coordinate Cu(II) centers to tetrahedral Cu(I) species by the action of the terminal alkyne employed in the catalytic reaction, under the conditions of the known Glaser coupling reaction. The generation of Cu(I) sites in the LDH structure facilitates the formation of a Cu(I)-acetylide intermediate [15, 33]. The organoazide can bind reversibly to the copper ion via the nitrogen atom proximal to carbon, forming the reactive complex 3. Then, the azide distal nitrogen attacks the acetylide-copper intermediate by reducing the electron density of the alkyne to afford a six-membered ring [16]. Moreover, the high concentration of the utilized terminal alkyne promotes the formation of oxidative alkynes homocoupling via Glaser coupling reaction as shown in Scheme 3 [33], resulting in a lower yield of the 1,2,3-triazole product (Figure 6).
A convenient synthesis of thiazol-2(3H)-one skeletons from a reaction involving terminal alkynes, elemental sulfur, and isocyanates
Published in Journal of Sulfur Chemistry, 2020
Fahimeh Heydari-Mokarrar, Reza Heydari, Malek-Taher Maghsoodlou, Alireza Samzadeh-Kermani
To get insight on the mechanism of the reaction, the reaction was conducted in stepwise manner and the results are shown in Scheme 1. The reaction conducted with phenylacetylene and elemental sulfur to form phenylethynylthiolate a was unsuccessful and instead the Glaser coupling product 6 or the dimeric product 7 was obtained (Scheme 1, a). As such, sodium phenylacetylide 8 was prepared in a separate step using 1a and 2 in the presence of NaH and was then reacted with isocyanate 3a. The study indicated that the presence of copper catalyst and base was necessary to form 4a (Scheme 1, b, c). Additionally, the reaction was conducted in competing mode with isocyanate 3a and isothiocyanate 9 to explore the effect of electrophilicity of the third coupling partner in reaction outcome. Control experiment indicated that the reaction proceeded almost entirely through isocyanate 3a which is most likely due to the greater potential of 3a for nucleophilic attack of phenylethynylthiolate species a (Scheme 1, d).