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This paper presents a study on the effects of oxygen functionalities on a mesoporous and graphitized carbon support (GNP, Graphene Nanoplatelets), on the catalytic activity of Pd/GNP catalysts in hydrogenation reactions. A functionalization method in liquid phase has been employed, using different oxidants (HNO3, H2O2, KMnO4), with the aim to tune the amount and the type of introduced oxygen functionalities. Preformed Pd nanoparticles have been used as Pd‐precursor to limit differences in metal particle size and dispersion on differently functionalized carbon. The catalytic behaviour in benzaldehyde hydrogenation/hydrogenolysis to benzyl alcohol and toluene revealed that the introduction of oxygen functionalities has a generally detrimental effect. NMR relaxometry studies highlighted the weaker interaction between the carbonyl group and the functionalized Pd/GNP surface than the non–functionalized Pd/GNP demonstrating that the origin of the different catalytic activity lies on the first step of the reaction. O‐functionalities also impacted on the Pd0/Pd2+ ratio at the surface which is an established parameter correlated to the reaction rate. [ABSTRACT FROM AUTHOR]

The Cover shows a micro‐kinetic model being applied to benzylic alcohol oxidation over metal nanoparticles. In their new Full Paper, A. Savara et al. report the first micro‐kinetic modeling of liquid phase benzylic alcohol oxidation over transition metal nanoparticles. The micro‐kinetic model was applied to palladium nanoparticles and enabled applying the concept of a sticking coefficient in solution. The kinetic simulations were able to reproduce the 18 trends observed in the responses of the six products when varying the alcohol concentration, oxygen pressure, and temperature. The mechanism used was based on surface science knowledge and an earlier study published in ChemCatChem. More information can be found in the Full Paper by A. Savara et al. et al. on page 2482 in Issue 15, 2016 (DOI: 10.1002/cctc.201600368). [ABSTRACT FROM AUTHOR]

The Cover shows an industrial landscape, where Au nanoparticles are used as catalysts for oxidation reactions.In their Full Paper, L. M. D. R. de Sousa Martins et al. demonstrate an efficient single‐pot oxidative functionalization of cyclohexane and benzyl and methylbenzyl alcohols under mild conditions with high selectivity, catalyzed by reusable Au nanoparticles on Al2O3, Fe2O3, ZnO, and TiO2. Au nanoparticles on Fe2O3 led to an unusual almost exclusive formation of cyclohexanol by control of reaction time, but Au nanoparticles on TiO2 had a remarkable catalytic effect on acetophenone yield. [ABSTRACT FROM AUTHOR]

Benzyl nitrite (PhCH2ONO) was previously identified as the pivotal intermediate in the HNO3-mediated oxidation of benzyl alcohol. Its acid-catalyzed decomposition yields benzaldehyde and HNO, the precursor of undesirable N2O. Most likely, an analogous mechanism is responsible for the formation of N2O during the oxidation of cyclohexanol and cyclohexanone to adipic acid, the largest industrial source of this important greenhouse gas. In this paper, the decomposition of benzyl nitrite is studied in more detail, allowing the kinetic isotope effect and the influence of substituents to be determined. A linear Evans-Polanyi correlation between the measured Arrhenius activation energies and the computed reaction energies was established. Furthermore, the differences in the reactivities of the substituted benzyl nitrites are reflected in the oxidation of the corresponding alcohols, and also affect the rate-determining step in the overall mechanism. The results of this study corroborate the importance of the nitrite intermediate in HNO3-based oxidation technology. [ABSTRACT FROM AUTHOR]

The best activity of bimetallic AuPd nanoparticles for alcohol oxidation reaction is usually achieved by adjusting the Au/Pd molar ratio. Herein, alloy AuPd nanoparticles of ∼2.5–3.5 nm, ranging from Au‐rich to Pd‐rich compositions, were synthesized through a sol‐immobilization method. A calcination step under air conditions caused an increase in size up to 5.5 nm, but also driven the segregation of Pd to the surface, which generated an Au rich core with Pd on the shell. At high Pd content, the shell structure is formed by PdO. The catalytic activity of Pd‐rich samples (1 : 1, 1 : 2 and 1 : 4 Au : Pd) for benzyl alcohol oxidation increased ∼4‐fold after calcination. Upon reduction with H2, surface PdO motifs are reduced to Pd that did not dissolve back into the AuPd alloy core, maintaining the metallic Pd shell. The catalytic activity decreased. Therefore, restructuring alloyed AuPd nanoparticles into core‐shell like structures with PdO in the shell is beneficial to the catalytic activity, but reduction of PdO layer was detrimental. These results provide new insights on the optimization of AuPd catalysts, considering not only the Au/Pd molar ratio, but also the importance of PdO, which was not anticipated in the previous literature. [ABSTRACT FROM AUTHOR]

Selective photooxidation of aromatic alcohols to corresponding aldehydes is a widely used model reaction for evaluation of performance of heterogeneous photocatalysts. A top example is the photocatalytic production of hydrogen peroxide via reduction of dioxygen with concomitant photooxidation of benzyl alcohol to benzaldehyde. Herein we demonstrate the ability of benzaldehyde to promote the auto‐photocatalytic oxidation of benzyl alcohol and produce large quantities of H2O2 in solvent‐free (no water) or biphasic (with water) systems even under nominally visible (>420 nm cut‐off filter) light irradiation. These results shed critical light on the plethora of research reports on photocatalytic H2O2 production in which benzyl alcohol was employed as electron donor. Since the autocatalytic pathway based on the photocatalytic activity of benzaldehyde formed during photocatalysis under such conditions cannot be neglected, the interpretations of photocatalytic performance are likely contentious and distorted in such reports. The use of benzyl alcohol as a model electron donor in photocatalytic studies should be therefore definitely discouraged. On the other hand, as we found that benzaldehyde‐mediated photocatalysis of H2O2 production proceeds also using alternative electron donors (e. g. ethanol), our results highlight the possible prospects for a more general use of benzaldehyde and other aromatic aldehydes in visible light‐driven photocatalysis. [ABSTRACT FROM AUTHOR]

Cover Feature: Au-Pd Selectivity-switchable Alcohol-oxidation Catalyst: Controlling the Duality of the Mechanism using a Multivariate Approach (ChemCatChem 13/2019) Keywords: SrCO3; Au-Pd nanoparticles; alcohol oxidation; factorial design SrCO3, Au-Pd nanoparticles, alcohol oxidation, factorial design. [Extracted from the article]

The Cover Feature shows a highly active Au‐Pd/Ti‐NT catalyst that has been produced by using colloidal synthesis and immobilization on essentially sodium‐free Ti‐nanotubes (NTs). In their Full Paper, M. Khawaji and D. Chadwick describe a new catalyst with excellent performance in the selective oxidation of benzyl alcohol. The superior catalytic activity of the catalyst is shown to be a result of the high metal dispersion on the external surfaces of Ti‐NTs, the narrow particle size distribution and the consistent formation of Au‐Pd mixed alloy nanoparticles in close to a 1:1 weight ratio. More information can be found in the Full Paper by M. Khawaji and D. Chadwick on page 4353 in Issue 23, 2017 (DOI: 10.1002/cctc.201700851). [ABSTRACT FROM AUTHOR]

A chemoselective method for the carbonylation of allylic substrates CH2=CHCH2X (X=OAc, OC(O)CH2CN, OPh, OEt, OC(O)OPh, OC(O)OiBu, N(H)C(O)Ph, N(Ph)C(O)Ph, N(H)Boc, N(Ph)Boc, Ph, CO2Bn, CN), leading to alkyl succinates with preservation of the X group, under Pd(II)‐catalyzed oxidative carbonylation conditions, has been developed. Our method shows a completely different inverse chemoselectivity with respect to the "classical" substitutive carbonylation of the allyl compounds, which is known to provide β,γ‐unsaturated carbonyl derivatives through the formation of a π‐allylpalladium intermediate. An accurate study, carried out using allyl acetate as model substrate, allowed to maximize the selectivity in the envisioned 2‐CH2X substituted succinates. The best catalyst is generated in situ by mixing Pd(TFA)2 (TFA=trifluoroacetate) and the N,N′‐di(anthracen‐9‐yl)butane‐2,3‐diimine ligand. p‐Benzoquinone was used as oxidant in presence of benzyl alcohol, which acts as a nucleophile and as a solvent, under 4 bar of CO at 20 °C. A combined effect of the ligand and the nucleophile, rationalized through DFT calculations, has been observed both in promoting the bis‐alkoxycarbonylation process and in preventing π‐allylpalladium‐mediated side reactions, allowing the attainment of succinate derivatives with moderate to good yields. [ABSTRACT FROM AUTHOR]

A new family of phosphine free organometallic ruthenium(II) catalysts (Ru1–Ru4) supported by bidentate NN Schiff base ligands (L1–L4 where L1=N,N‐dimethyl‐4‐((2‐phenyl‐2‐(pyridin‐2‐ylmethyl)hydrazineylidene)methyl) aniline, L2=N,N‐diethyl‐4‐((2‐phenyl‐2‐(pyridin‐2‐ylmethyl)hydrazineylidene)methyl)aniline, L3=N,N‐dimethyl‐4‐((2‐phenyl‐2‐(pyridin‐2‐yl)hydrazineylidene)methyl)‐ aniline and L4=N,N‐diethyl‐4‐((2‐phenyl‐2‐(pyridin‐2‐yl)hydrazineylidene)methyl) aniline) was prepared and characterized. These half‐sandwich complexes acted as catalysts for C−C bond formation and exhibited excellent performance in the dehydrogenative coupling of ketones and amides. In the synthesis of C–C bonds, alcohols were utilized as the alkylating agent. A broad range of substrates, including sterically hindered ketones and alcohols, were well tolerated under the optimized conditions (TON up to 47000 and TOF up to 11750 h−1). This ruthenium (II) catalysts were also active towards the dehydrogenative cyclization of o‐amino benzyl alcohol for the formation of quinolines derivatives. Various polysubstituted quinolines were synthesized in moderate to excellent yields (TON up to 71000 and TOF up to 11830 h−1). Control experiments were carried out and the ruthenium hydride intermediate was characterized to support the reaction mechanism and a probable reaction pathway of dehydrogenative coupling for the C−C bond formation has been proposed. [ABSTRACT FROM AUTHOR]

Zeolite catalysts with pronounced two‐dimensional (2D) morphologies, specifically 2D MFI nanosheets composed of multilamellar stacks of MFI nanosheets, are hypothesized to offer accessibility advantages in catalytic reactions involving large, bulky molecules. The Si/Al ratio of zeolite catalysts is an important parameter determining their performance. However, the effect of Si/Al ratio on catalytic reactivity is not well understood in 2D zeolite catalysts. To provide further insight into this issue, the catalytic performance of 2D MFI nanosheet materials with different Si/Al ratios is compared using the liquid phase Friedel‐Crafts alkylation of mesitylene with benzyl alcohol & the self‐etherification of benzyl alcohol that occurs in parallel, both of which are catalyzed by Brønsted acid sites. The turnover frequency (TOF) of the catalysts is found to decrease with decreasing Si/Al ratio, with the etherification reaction being the main contributor to this trend. When the same reaction is carried out in the presence of a bulky poison, 2,6 di‐tert‐butylpyridine (DTBP), to selectively deactivate the external acid sites, only the etherification reaction of benzyl alcohol takes place in the micropores of the 2D MFI catalyst and the effectiveness factor is found to decrease with decreasing Si/Al ratio. The single component adsorption isotherms of benzyl alcohol show that the uptake normalized per acid site decreases with decreasing Si/Al ratio. Thus, increasing the density of acid sites in the micropores by decreasing the Si/Al ratio makes it more difficult for the reactant molecules to access them, as demonstrated by the decrease in TOF and the effectiveness factor. While the micropore reactions (benzene alkylation, alcohol etherification) showed a clear trend with Si/Al ratio, the reaction catalyzed on the external surface (mesitylene alkylation) did not, showing distinct differences in reactivity. [ABSTRACT FROM AUTHOR]

In this work, a highly active Au-Pd/Ti-NT catalyst has been produced by using colloidal synthesis and immobilisation on essentially sodium-free Ti-nanotubes (NTs). The new catalyst has markedly superior catalytic activity (turnover frequency>19 000 h−1) for the selective oxidation of benzyl alcohol compared with similar catalysts reported in the literature, and to Au-Pd catalysts supported on Ti-NTs prepared by adsorption, as well as conventional Au-Pd/TiO2 prepared by impregnation. The superior catalytic activity of the catalyst is shown to be a result of the high metal dispersion on the external surfaces of Ti-NTs, the narrow particle size distribution and the consistent formation of Au-Pd mixed alloy nanoparticles in close to a 1:1 weight ratio. In repeated use, the Au-Pd/Ti-NT catalyst showed only a modest fall in activity, which is shown by FTIR to be associated mainly with the irreversible adsorption of benzoic acid and benzyl benzoate by the catalyst. [ABSTRACT FROM AUTHOR]

Herein, chiral Mn-aminopyridine complexes have been shown to catalyze the oxidation of alkylarenes to enantiomerically enriched 1-arylalkanols with hydrogen peroxide. The observed enantiomeric excess values result from the direct enantioselective benzylic C−H hydroxylation, accompanied by stereoconvergent oxidative kinetic resolution of the resulting alcohol. Testing several ( S, S)-bipyrrolidine derived Mn complexes has revealed a novel catalyst ( 6) that exhibits the best kinetic resolution in the series ( krel up to 8.8), along with sufficient reactivity and efficiency (>1000 catalytic turnovers). The mechanistic study of the Mn-mediated alcohol oxidation witnesses electrophilic active species ( ρ=−1.2), with rate-limiting H abstraction ( kH/ kD=2.2), followed by oxygen rebound and dehydration of the resulting gem-diol to form the ketone. Intriguingly, while for the resolution of the relatively bulky 1,2-diphenylethanol, krel is virtually constant throughout the reaction, for less bulky alcohols, krel increases with increasing conversion, in line with the rising optical purity of the 1-arylalkanol. The latter participates in the oxidation as an auxiliary ligand, assisting the chiral recognition. This effect is related to the previously described asymmetric autocatalysis and asymmetric autoinduction, but is not identical with either of those, with the differences being discussed. To unambiguously identify this effect, the term asymmetric autoamplification ( chiral autoamplification) is proposed. [ABSTRACT FROM AUTHOR]

CuI N-heterocycle thiolate clusters efficiently catalyze the acceptorless dehydrogenation of alcohols at 70 °C. A variety of secondary/primary benzylic, allylic, and aliphatic alcohols are dehydrogenated to the corresponding ketones and aldehydes in high yields of isolated product upon release of H2. This simple catalytic system is involved in the synthesis of imines through the one-pot reaction of alcohols and amines. [ABSTRACT FROM AUTHOR]

Thin-sheet sinter-locked Ti-microfiber-supported binary-oxide-nanocomposite catalysts engineered on the micro- to macroscales were developed for the gas-phase aerobic oxidation of benzyl alcohol to benzaldehyde. The catalysts demonstrated higher activity than single-oxide and noble-metal catalysts with good stability and regenerability. The catalysts were obtained by placing transient metal (e.g., Ni, Co, Cu, Mn) nitrates onto a Ti-microfiber surface by impregnation, and the supported nitrates were subsequently in situ transformed into the binary-oxide composites in the real reaction stream at 300 °C. Among them, CoO-2.5-CuO x-2.5/Ti-fiber was found to be the best catalyst; it delivered 93.5 % conversion of benzyl alcohol (b.p. 210 °C) with 99.2 % selectivity to benzaldehyde at 230 °C. In situ induced formation of 'CoO@Cu2O' ensembles (i.e., larger CoO nanoparticles partially covered with smaller Cu2O clusters and/or nanoparticles) was identified, which by nature resulted in a large Cu2O-CoO interface and led to a significant improvement in the low-temperature activity. [ABSTRACT FROM AUTHOR]