103-50-4Relevant articles and documents
Cobalt-Catalyzed Secondary Alkylation of Arenes and Olefins with Alkyl Ethers through the Cleavage of C(sp2)-H and C(sp3)-O Bonds
Dong, Xunqing,Li, Qun,Li, Guigen,Lu, Hongjian
, p. 13402 - 13413 (2018)
A novel cobalt-catalyzed C-H alkylation of arenes and olefins is achieved with (pyridin-2-yl)isopropyl amine as an N,N-bidentate directing group. Different linear, branched, and cyclic alkyl ethers were used as practical secondary alkylating reagents through cleavage of C(sp3)-O bond, providing an efficient approach to the synthesis of verstile o-alkylated arylamides and tetrasubstituted acrylamides. Mechanistic studies indicate that cleavage of the inert C(sp3)-O bond involves a cobalt-promoted radical process and that cleavage of the inert C(sp2)-H bond by a cobalt catalyst is a rate-limiting step.
Post-synthesis deposition of mesoporous niobic acid with improved thermal stability by kinetically controlled sol-gel overcoating
Du, Yuan-Peng,Héroguel, Florent,Nguyen, Xuan Trung,Luterbacher, Jeremy S.
, p. 23803 - 23811 (2019)
Niobia is a well-known solid acid catalyst owing to its intrinsic Br?nsted and Lewis acidity. However, catalyst development with this oxide has been limited by our ability to control its pore structure and thermal stability. Here we report a novel post-synthetic approach for preparing mesoporous niobia catalysts. This method relies on controlling the kinetics of niobium(v) ethoxide to deposit conformal Nb2O5 overcoats on SBA-15 in a typical St?ber solution. Full Nb2O5 coverage over the mesopores of SBA-15 was achieved by adding 4 monolayer equivalents of precursor (4Nb2O5?SBA-15), which was verified by X-ray photoelectron spectroscopy. This overcoated SBA-15 had a high surface area and retained a narrow as well as ordered pore size distribution. Importantly, the typical structural transition from the amorphous to pseudo-hexagonal Nb2O5 phase did not occur with the overcoat after calcination at 773 K. Limiting this crystallization imparts an unprecedented thermal stability to our niobia overcoat, which enables the acid sites to be well preserved after catalyst regeneration. Furthermore, 4Nb2O5?SBA-15 showed higher yields than commercial niobia (HY-340) and lab-synthesized bulk niobia in two probe reactions: xylose dehydration to furfural and Friedel-Crafts alkylation. In both cases, the improvement could be explained by the unique structural features of the niobia overcoat, including a favorable ratio of Br?nsted and Lewis acid sites in the case of xylose dehydration and a high proportion of isolated Nb-OH groups for the alkylation reaction. Such structural features and unprecedented thermal stability provide additional tools for synthetizing unique solid acid catalysts using a simple post-synthesis deposition method.
Sulfonated polypyrene (S-PPR) as efficient catalyst for esterification of carboxylic acids with equimolar amounts of alcohols without removing water
Tanemura, Kiyoshi,Suzuki, Tsuneo
, p. 1972 - 1975 (2013)
Sulfonated polypyrene (S-PPR) efficiently catalyzed the reactions between carboxylic acids and equimolar amounts of alcohols with and without heptane to give the corresponding esters in good to excellent yields. Esterification was carried out at 110 °C without removing water. Transesterification of carboxylic esters with a slight excess of alcohols smoothly proceeded without heptane to give the corresponding esters in good yields. For these reactions, S-PPR was recycled without significant loss of activities.
Iodine induced transformations of alcohols under solvent-free conditions
Stavber, Gaj,Zupan, Marko,Stavber, Stojan
, p. 8463 - 8466 (2006)
Iodine has been shown to be an efficient catalyst for transformations of alcohols under solvent-free conditions. In the presence of 5% of iodine, tertiary alcohols underwent dehydration forming the corresponding alkenes, while in the case of 2-phenylpropane-2-ol cyclodimerisation to 1,1,3-trimethyl-3-phenylindane took place. Secondary and primary benzyl alcohols under the same conditions gave the corresponding ethers.
Spontaneous water release inducing nucleation during the nonaqueous synthesis of TiO2 nanoparticles
Zimmermann, Mandy,Garnweitner, Georg
, p. 8562 - 8568 (2012)
The formation of anatase nanoparticles by reaction of titanium(iv) isopropoxide in benzyl alcohol was studied. In contrast to previous reports on the nonaqueous synthesis, in this system the particle formation occurs within a very limited time span in the course of the synthesis, concurrently to a fast step-type pressure increase within the closed reaction system. By Karl Fischer titration and 1H NMR spectroscopy of both the liquid and the gaseous phase at different stages of the reaction, it is shown that water formation occurs during the pressure increase due to catalytic ether formation from benzyl alcohol. The generated water leads to instant nucleation and fast growth of crystalline nanoparticles, which is traced by powder X-ray diffraction as well as small-angle X-ray scattering and thereby shown to play a crucial role in the particle formation process. The Royal Society of Chemistry.
Niobic acid nanosheets synthesized by a simple hydrothermal method as efficient Bronsted acid catalysts
Fan, Wenqing,Zhang, Qinghong,Deng, Weiping,Wang, Ye
, p. 3277 - 3287 (2013)
This paper reports a novel bottom-up hydrothermal route for the synthesis of niobic acid nanosheets. This route is simpler and greener than the conventional top-down and multistep route for the synthesis of hydrated metal oxide nanosheets via exfoliation of layered compounds, which typically requires the use of bulky organic cations. We have clarified that the pH of the suspension for hydrothermal treatment, the hydrothermal temperature and time, and the presence of NH4+ play roles in determining the morphology of the product. We propose that the nanosheet is formed from amorphous niobic acid nanoparticles through a dissolution-crystallization mechanism. The obtained niobic acid nanosheets are uniform with a thickness of ～2 nm and uniquely possess mainly Bronsted acid sites. As compared to the conventional amorphous niobic acid and several other typical solid acid catalysts, the niobic acid nanosheet synthesized by our bottom-up method exhibits significantly higher activity and selectivity for the Friedel-Crafts alkylation of anisole with benzyl alcohol. We have further demonstrated that our niobic acid nanosheet is a water-tolerant and efficient catalyst for the hydrolysis of inulin, a polysaccharide-based biomass, into fructose.
Preparation of a platinum nanoparticle catalyst located near photocatalyst titanium oxide and its catalytic activity to convert benzyl alcohols to the corresponding ethers
Akiyama, Toshiki,Arisawa, Mitsuiro,Harada, Kazuo,Honma, Tetsuo,Naka, Hiroshi,Saito, Susumu,Wada, Yuki
, p. 22230 - 22237 (2021)
A novel platinum nanoparticle catalyst closely located near the surface of titanium oxide, PtNP/TiO2, has been prepared. This catalyst has both the properties of a photocatalyst and a metal nanoparticle catalyst, and acquired environmentally friendly catalytic activity, which cannot be achieved by just one of these catalysts, to afford ethers from benzyl alcohols under the wavelength of 420 nm.
Versatile low-loaded mechanochemically synthesized supported iron oxide nanoparticles for continuous flow alkylations
Balu, Alina M.,Pineda, Antonio,Obermayer, David,Romero, Antonio A.,Kappe, C. Oliver,Luque, Rafael
, p. 16292 - 16295 (2013)
A novel and highly versatile mechanochemically synthesized low-loaded (0.25 wt.%) supported iron oxide nanocatalyst has been demonstrated to be highly active and selective for the production of o- and p-benzylmethylbenzene (preferentially) C-C alkylated products in the continuous flow alkylation of toluene with benzyl chloride as compared to the etherification product (dibenzyl ether) observed in the alkylation of toluene with benzyl alcohol. The low quantities of highly accessible iron oxide nanoparticles on the external surface of an aluminosilicate support provided versatile acidic sites that were able to promote both the alkylation of toluene with benzyl alcohol and benzyl chloride. ICP-MS analysis revealed that the catalyst is highly stable and does not significantly leach under the investigated conditions, providing solid evidence of an iron-catalysed heterogeneous protocol. The Royal Society of Chemistry 2013.
Zinc-catalyzed reduction of aldehydes with a hydrosilane leading to symmetric ethers and silyl ethers
Sakai, Norio,Nonomura, Yoshifumi,Ikeda, Reiko,Konakahara, Takeo
, p. 489 - 491 (2013)
The efficient reductive etherification of aromatic or aliphatic aldehydes using a reducing system that combines Zn(OTf)2 with either TMDS or Et3SiH is described. The present reducing system can also be applied to the hydrosilylation of aromatic aldehydes having either a strong electron-withdrawing group or a pyridine ring.
Novel reactions of ethylene acetals with silyl-substituted nucleophiles. A mild and efficient procedure for the synthesis of homoallyl alkyl ethers and unsymmetrical dialkyl ethers
Suzuki, Takeshi,Oriyama, Takeshi
, p. 1263 - 1269 (1999)
Efficient one-pot synthesis of homoallyl alkyl ethers and dialkyl ethers was performed by the allylation and reduction of ethylene acetals with allyltrimethylsilane and t-butyldimethylsilane, respectively, in the presence of alkoxytrimethylsilane.
