19310-29-3Relevant articles and documents
Operation of the boomerang mechanism in olefin metathesis reactions promoted by the second-generation Hoveyda catalyst
Bates, Jennifer M.,Lummiss, Justin A. M.,Bailey, Gwendolyn A.,Fogg, Deryn E.
, p. 2387 - 2394 (2014)
A long-standing question in olefin metathesis centers on whether the release-return (boomerang) mechanism contributes to the productivity of Hoveyda-class catalysts. According to this mechanism, a molecule of o-isopropoxystyrene (A) is liberated during catalyst initiation, but recaptures the active catalyst following metathesis. The relevance of this pathway for the second-generation Hoveyda catalyst HII was assessed in metathesis of 1,1-and 1,2-disubstituted olefins. Crossover studies with 13C-labeled A*, as well as competition experiments involving ring-closing or cross metathesis (RCM, CM) in the presence of A (equimolar with HII) indicated rapid reuptake of styrenyl ether. The crossover studies indicated highly efficient catalyst initiation, with the entire catalyst charge being activated before metathesis was complete. In a comparative study involving CM of anethole with methyl acrylate, sustained activity was shown for HII, whereas the second-generation Grubbs catalyst GII was rapidly deactivated. These data demonstrate that the release-return mechanism is indeed operative for HII in these demanding metathesis reactions, and that facile shuttling from a protected recapture cycle into the productive metathesis cycle contributes to the superior performance of HII relative to GII.
E-senegasaponins a and b, Z-senegasaponins a and b, Z-senegins II and III, new type inhibitors of ethanol absorption in rats from Senegae Radix, the roots of Polygala senega L. Var latifolia Torrey et Gray
Yoshikawa,Murakami,Ueno,Kadoya,Matsuda,Yamahara,Murakami
, p. 350 - 352 (1995)
New inhibitors of ethanol absorption, E-senegasaponins a and b, Z-senegasaponins a and b, Z-senegins II and III, were isolated from Senegae Radix, the roots of Polygala senega L. var latifolia TORREY et GRAY, together with senegins II and III. Their chemical structures have been elucidated on the basis of chemical and physicochemical evidence, and the geometrical isomeric structures of methoxycinnamoyl moiety in each saponin were found to show tautomer-like behavior. The inhibitory effects of senegasaponins, senegins, and their related compounds have been examined, and some structure-activity relationships have been found.
Benzimidazol-2-ylidene ligated palladacyclic complexes of N,N-dimethylbenzylamine - Synthesis and application to C-C coupling reactions
Green, Kerry-Ann,Maragh, Paul T.,Abdur-Rashid, Kamaluddin,Lough, Alan J.,Dasgupta, Tara P.
, p. 38 - 43 (2016)
Palladacyclic complexes derived from N,N-dimethylbenzylamine (dmba) and the benzimidazol-2-ylidene ligands: 1,3-di(cyclohexyl)benzimidazol-2-ylidene (BzImCy), 1,3-di(tert-butyl)benzimidazol-2-ylidene (BzImtBu) and 1,3-di(1-adamantyl)benzimidazol-2-ylidene (BzImAd) were prepared. The yield for (BzImCy)Pd(Cl)dmba (2a) was 72% but yields for the more sterically encumbering analogues: (BzImAd)Pd(Cl)dmba (2b) and (BzImtBu)Pd(Cl)dmba (2c) were 34% and 38%, respectively. The complexes were obtained as off-white, moisture- and air-stable crystalline solids and were characterized by 1H NMR and 13C NMR spectroscopy, CHN analysis and IR spectroscopy. Complex 2c was further characterized by X-ray diffraction studies. The catalytic activity of all three complexes was explored for the Suzuki-Miyaura and Heck-Mizoroki coupling reactions of simple aryl bromides.
Pd-Catalyzed desulfitative arylation of olefins by: N -methoxysulfonamide
Ojha, Subhadra,Panda, Niranjan
supporting information, p. 1292 - 1298 (2022/02/19)
A novel Pd-catalyzed protocol for the desulfitative Heck-type reaction of N-methoxy aryl sulfonamides with alkenes was reported. The cross-coupling reaction was performed successfully with a variety of olefins to obtain aryl alkenes. Different substituents on the aromatic ring of N-methoxysulfonamides were also found to be compatible with the reaction conditions. Expectedly, the reaction proceeds through CuCl2-promoted generation of the nitrogen radical and subsequent desulfonylation under thermal conditions to afford the aryl radical for the Pd-catalyzed coupling reaction. N-Methoxysulfonamide was further exploited for the synthesis of symmetrical biaryls in the presence of CuCl2. This journal is
Triazine-hyperbranched polymer-modified magnetic nanoparticles-supported nano-cobalt for C–C cross-coupling reactions
Hajipour, Abdol R.,Sadeghi, Shaghayegh
, p. 3219 - 3233 (2021/08/06)
Design of hyperbranched polymers (HBPs) and crafting them in catalytic systems especially in organic chemistry are a relatively unexplored domain. This paper reports the utilization of triazine-hyperbranched polymer (THBP)-coated magnetic chitosan nanoparticles (MCs) as stabilizing matrix for cobalt nanoparticles. Cobalt nanoparticles were fabricated by coordination cobalt(II) ions with amine-terminated triazine polymer and then reduced into Co(0) using sodium borohydride in aqueous medium. The Co(0)-THBP@MCs were fully characterized by FT-IR, SEM–EDX, TEM, and TGA analyses. The presence of metallic cobalt was determined by ICP and XRD techniques. This novel hyperbranched polyaromatic polymer-encapsulated cobalt nanoparticles showed high catalytic activity in Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions. Heck and Suzuki reactions were carried out using 0.35 and 0.4?mol% of cobalt nanoparticles in which the turnover number (TON) values were calculated as 271 and 225, respectively. In addition, the produced heterogeneous catalyst could be recovered and reused without considerable loss of activity. Oxygen stability and high reusability over 7 runs with trace leaching of the cobalt into the reaction media as well as moisture stability of the immobilized cobalt nanoparticles are their considerable worthwhile advantages.
