ChemCatChem

The cover picture shows furfuryl alcohol polymerization, an important reaction during the mineral acid treatment in aqueous solution. The identities of molecular intermediates and reaction mechanisms during the polymerization were investigated by Raman spectroscopy and density functional theory calculations. Detailed thermochemistry of protonation of furfuryl alcohol, initiation of polymerization, and formation of conjugated dienes and diketonic species were predicted using computational methods. In the Full Paper on p. 1451 ff., Taejin Kim, Rajeev S. Assary et al. report that a strong aliphatic CC band in the measured and calculated Raman spectra support the formation of conjugated diene structure, as a result of acid catalyzed furfuryl alcohol polymerization, compared to diketone structure. This combined experimental and theoretical investigation provides a detailed molecular understanding of polymerization during the conversion of biomass to platform chemicals for alternative fuels and industrial chemicals. The initials IACT stand for the Institute for Atom-efficient Chemical Transformations, an Energy Frontier Research Center funded by the U.S. Department of Energy.

More to this than meets the eye: The concept of terpyridine complexes and catalysis is reviewed critically with respect to applications in conventional organometallic catalysis, as well as in electro- and photcatalytic processes.

Getting fresh with iridium: Water is the solvent of choice in the N-alkylation of amines with iridium catalysts. Numerous secondary and tertiary amines can be assembled with excellent yields and chemoselectivity.

The first cut is the deepest: Hydrogenolysis is now applicable to the inert C(aryl)O bonds in aryl ethers by using a soluble nickel complex ligated by N-heterocyclic carbenes. The protocol is potentially useful in the depolymerization of aryl ether-based biopolymers, such as lignin and coal. COD: 1,5-cyclooctadiene.

Defects beat faces: It is proposed that, for soluble metal nanoparticles, ideally the turnover number (TON) is determined by using the titrated number of active catalytic sites. However, in the absence of reliable titration methods, the TON figures should be reported as the number of moles of reactants consumed per mol of soluble metal nanoparticle and the figures should also be corrected by the number of exposed surface atoms by using the metal atom's magic number approach.

Multiple talents: A coordinatively unsaturated rhodium-hydride (RhH) species is formed from [Rh(OH)(cod)]₂ without any additional hydride sources. The formation of the RhH species is confirmed by using ¹H NMR analysis and hydride transfer reactions using deuterated olefins. This RhH species displays excellent catalytic performances in the isomerization of olefins.

Reduction for oxidation: After preliminary treatment with molecular hydrogen, Au/TiO₂ and Au/Al₂O₃ catalysts were able to induce O₂ isotope exchange at mild conditions (−15 °C), which is believed to proceed through highly reactive surface oxygen species. However, the relative intensity of such an exchange is markedly different (see picture) and is in accordance with the diverse profiles of ethanol oxidation over gold nanoparticles supported on TiO₂, Al₂O₃, and SiO₂ matrixes.

Al₂O₃-supported copper nanoparticles prepared from cetyltrimethylammonium bromide (CTAB) capped copper nanoparticles are effective water-gas shift catalysts. High activity can be explained by the presence of well-dispersed Cu nanoparticles on the alumina support due to strong interaction between CTAB and the Cu nanoparticles.

It doesn′t cost a dime: A nickel-based system that catalyzes the aromatic amination of aryl chlorides is presented. Starting from a simple Ni(II) salt, aliphatic phosphonium-based ionic liquids (ILs) were found to stabilize the nickel nanoparticles formed in situ during the reaction. The IL also enables successful recycling of the system after the reaction.

Tungstate turnpike: Mesoporous polymer-supported polyoxotungstate acts as an effective heterogeneous catalyst in the liquid-phase olefin epoxidation using H₂O₂. The effectiveness is attributed to the optimized hydrophobic/hydrophilic balance within the uniform mesoporous environment. Furthermore, the catalyst can be recycled without significant loss of activity.

Adamant about this: A variety of aryl and heteroaryl propargyl ethers are obtained in good to excellent yields from activated and non-activated aryl bromides and chlorides in the presence of a sterically hindered, air-stable ligand by using a general palladium-catalyzed synthesis. Our protocol complements the known syntheses for alkynyl aryl ethers and 2H-1-benzopyrans and should find further applications in organic synthesis.

Simple as that: A novel crystalline microporous titanosilicate (Ti-COE-4) with functionalized hydroxyl groups and medium micropore size (0.55 nm) is successfully synthesized through dimethylsilylation and calcination. The synergism of hydroxyl groups with active Ti sites in Ti-COE-4 significantly improves its catalytic activities in oxidation reactions.

Elite selection: The selective oxidation of allylic and benzylic compounds to the corresponding carbonyl compounds (enones), using H₂O₂ as oxidant and methanol as solvent over chromiumincorporated mesoporous zirconium phosphate, is evaluated.

I′m with the band: The strong aliphatic CC band (1654 cm⁻¹) observed in the measured Raman spectra is crucial evidence to understand the polymerization reaction mechanism (see figure). The formation of a conjugated diene structure instead of a diketone structure is involved in the furfuryl alcohol polymerization reaction. The B3LYP level of theory also indicates that the formation of diene is preferred over the formation of diketone.

The Lewis acid makes the difference! Different spectroscopic methods (UV/vis, ATR-IR, and Raman) were applied in situ as well as ex situ to elucidate the mode of action of different Lewis acids in the [3+3] cyclization reaction of a 1,3-bis(silyloxy)-1,3-butadiene with a ketenacetale. The different interaction of two different Lewis acids with the ketenacetale was spectroscopically characterized and identified as the crucial step, which influences the subsequent reaction pathways.

Rest, then have a go: The oxidation of (1R,2S)-1-phenyl-1,2-propanediol [(1S,2R)-1] using Baker's yeast gives (S)-1-phenyl-2-hydroxy-1-propanone (2) in 64 % yield and 93 % ee. Cells resting time and acetone (5 vol %) are used to improve the bio-oxidation. The oxidation is probably realized by an oxidase, which depends on molecular oxygen. A kinetic resolution experiment gave (1S,2R)-1 in>99 % ee from (±)-anti-1.

A catalyst to keep you from cracking up: The hydrocracking of anthracene was catalyzed by NiFe/HZSM-5 to produce ethyl biphenyl in yields as high as 34 % in the presence of water. Water in the reaction system could enhance CC bond breakage and promote the isomerization and hydrogen transfer reactions. The liquid product yields in the hydrocracking of the Daqing residue oil could also increase in the presence of water, which is consistent with the hydrocracking of anthracene.

Potassium is the answer: Adding potassium to the MoS₂ catalyst is necessary to achieve a high activity and selectivity from CH₃SH from H₂S-containing syngas. Acting as adsorption centers, the surface potassium cations promote the disproportionation of carbonyl sulfide to CO₂ and CS₂, but hinder the OC and CS bond cleavage, which is the preferred reaction on the sulfur vacancies of MoS₂.

The BIMINAP ligand makes it possible! 5-vinyl-2-pyrazolines were obtained from C-homoallylhydrazones through Pd catalyzed intramolecular CH oxidative allylic amination by using the atropochiral electron-poor BIMINAP ligand. BIMINAP=formal contraction of the acronyms BIMIP=2,2′-bis(diphenylphosphino)-1,1′-bibenzimidazole and BINAP=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl.

Control your children without being harsh: Herein we present a simple system for the otherwise difficult hydrogenolysis of nitriles, imines, and amines. This system can achieve high yields without using harsh conditions. Investigations into the mechanics of this system aid our understanding of what has been thought to be a simple process.

Straight on through to the other side: Catalytic membrane reactors based on solid-state oxygen conductors enabled us to achieve high ethylene productivity through the oxidative dehydrogenation of ethane. The selectivity is maximized by preventing the direct contact of molecular oxygen and hydrocarbons, by properly selecting the temperature and inlet gas flow rates, and by using methane as a diluting agent.