25105-94-6Relevant articles and documents
Interfacial Control of Catalytic Activity in the Aldol Condensation: Combining the Effects of Hydrophobic Environments and Water
Singappuli-Arachchige, Dilini,Kobayashi, Takeshi,Wang, Zhuoran,Burkhow, Sadie J.,Smith, Emily A.,Pruski, Marek,Slowing, Igor I.
, p. 5574 - 5582 (2019/06/18)
Aminopropyl-functionalized mesoporous silica nanoparticles (AP-MSN) catalyze aldol condensations. The activity of AP-MSN decreases with increasing solvent polarity due to the stabilization of ion pairs formed between acidic silanol groups and the amines, which ultimately decreases the number of catalytically active amine sites. However, the reaction in water is faster than expected on the basis of polarity, because water limits the formation of Schiff bases that are also responsible for blocking active sites. In this work, we combined the action of water with a low-local-polarity environment around the catalytic sites of AP-MSN to maximize active site availability and catalyst performance. We specifically demonstrate how the local polarity of AP-MSN can be controlled by modifying its surface with varying concentrations of hexyl groups and how the dielectric constant of the silica-water interface can be determined using the solvatochromic probe Prodan. The catalytic activities of hexyl-modified AP-MSN in water were inversely proportional to their interfacial dielectric constants and were significantly higher (roughly by a factor of 4) than those of AP-MSN in anhydrous solvents of comparable polarities. Producing low-local-polarity environments in aqueous AP-MSN also enhanced the sensitivity of the aldol reaction to the electronic effects of substituents in the substrate. The enhancement of catalytic activity by low interfacial polarity was also observed in other amine-catalyzed C-C bond forming reactions such as the Henry and vinylogous aldol reactions. Overall, our results demonstrate that the catalytic activity of AP-MSN can be controlled by the synergistic action of water and a low interfacial dielectric constant.
Stabilized Ru[(H2O)6]3+ in Confined Spaces (MOFs and Zeolites) Catalyzes the Imination of Primary Alcohols under Atmospheric Conditions with Wide Scope
Mon, Marta,Adam, Rosa,Ferrando-Soria, Jesús,Corma, Avelino,Armentano, Donatella,Pardo, Emilio,Leyva-Pérez, Antonio
, p. 10401 - 10406 (2018/10/24)
Imines are ubiquitous intermediates in organic synthesis, and the metal-mediated imination of alcohols is one of the most direct and simple methods for their synthesis. However, reported protocols lack compatibility with many other functional groups since basic supports/media, pure oxygen atmospheres, and/or released hydrogen gas are required during reaction. Here we show that, in contrast to previous metal-catalyzed methods, hexa-aqueous Ru(III) catalyzes the imination of primary alcohols with very wide functional group tolerance, at slightly acid pH and under low oxygen atmospheres. The inorganic metal complex can be supported and stabilized, integrally, within either faujasite-type zeolites (Y and X) or a metal organic framework (MOF), to give a reusable heterogeneous catalyst which provides an industrially viable process well below the flammability limit of alcohols and amines.
Effective catalysis of imine metathesis by means of fast transiminations between aromatic-aromatic or aromatic-aliphatic amines
Ciaccia, Maria,Pilati, Silvia,Cacciapaglia, Roberta,Mandolini, Luigi,Di Stefano, Stefano
supporting information, p. 3282 - 3287 (2014/05/06)
This paper reports on a quantitative investigation of rates of amine-imine exchange reactions of primary amines with their benzylidene derivatives in organic solvents at room temperature. Exchange reactions involving aromatic-aromatic or aromatic-aliphati
