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The chain–walking of terminal alkenes (also called migration or isomerization reaction) is currently carried out in industry with unselective and relatively costly processes, to give mixtures of alkenes with significant amounts of oligomerized, branched and reduced by–products. Here, it is shown that part–per–million amounts of a variety of commercially available and in–house made ruthenium compounds, supported or not, transform into an extremely active catalyst for the regioselective migration of terminal alkenes to internal positions, with yields and selectivity up to >99% and without any solvent, ligand, additive or protecting atmosphere required, but only heating at temperatures >150 °C. The resulting internal alkene can be prepared in kilogram quantities, ready to be used in nine different organic reactions without any further treatment. The chain-walking of terminal alkenes is an industrially relevant reaction. Here, the authors show that part-per-million amounts of a variety of ruthenium compounds catalyze the reaction in yields and selectivity up to >99%, without any solvent or additive.

Researchers have investigated for decades a suitable catalyst to selectively synthesize epoxides from alkenes with air. Here we show that a selective aerobic epoxidation of industrial alkyl alkenes in liquid phase occurs without any catalyst, solvent nor additive, just placing the neat alkene under 3–5 bar of O 2 and heating between 100 and 200 °C. The reaction can be performed in either an autoclave, a stirring vessel with air bubbling or even a simple open flask, provided that any metal piece is not in contact with the reaction. Alkyl epoxides are directly obtained, after air venting, in yields and selectivity up to 90%. The simplicity of the set-up (just the neat liquid alkene and air) allows to engage the epoxidation reaction with either a previous alkene formation (upstreaming) or a later epoxide opening (downstreaming) reactions, to achieve a variety of industrially-relevant organic products in one-pot. Researchers have investigated for decades a suitable catalyst to selectively synthesize epoxides from alkenes with air, in order to circumvent harsh oxidant agents. Here, the authors show that a selective aerobic epoxidation of industrial alkyl alkenes in liquid phase occurs without any catalyst, solvent nor additive, just placing the neat alkene under 3–5 bar of O2 and heating between 100 and 200 °C.

The surface of SBA‐15 mesoporous silica was modified by N‐hydroxyphthalimide (NHPI) moieties acting as immobilized active species for aerobic oxidation of alkylaromatic hydrocarbons. The incorporation was carried out by four original approaches: the grafting‐from and grafting‐onto techniques, using the presence of surface silanols enabling the formation of particularly stable O−Si−C bonds between the silica support and the organic modifier. The strategies involving the Heck coupling led to the formation of NHPI groups separated from the SiO2 surface by a vinyl linker, while one of the developed modification paths based on the grafting of an appropriate organosilane coupling agent resulted in the active phase devoid of this structural element. The successful course of the synthesis was verified by FTIR and 1H NMR measurements. Furthermore, the formed materials were examined in terms of their chemical composition (elemental analysis, thermal analysis), structure of surface groups (13C NMR, XPS), porosity (low‐temperature N2 adsorption), and tested as catalysts in the aerobic oxidation of p‐xylene at atmospheric pressure. The highest conversion and selectivity to p‐toluic acid were achieved using the catalyst with enhanced availability of non‐hydrolyzed NHPI groups in the pore system. The catalytic stability of the material was additionally confirmed in several subsequent reaction cycles. Various strategies were used to graft N‐hydroxyphthalimide groups onto the surface of SBA‐15 mesoporous silica by the formation of O−Si‐C bonds in order to activate them in the aerobic oxidation of p‐xylene.

Ultrasmall silver clusters in reduced state are difficult to synthesize since silver atoms tend to rapidly aggregate into bigger entities. Here, we show that dimers of reduced silver (Ag 2 ) are formed within the framework of a metal–organic framework provided with thioether arms in their walls (methioMOF), after reduction with NaBH 4 of the corresponding Ag + -methioMOF precursor. The resulting Ag 2 -methioMOF catalyzes the methanation reaction of carbon dioxide (CO 2 to CH 4 hydrogenation reaction) under mild reaction conditions (1 atm CO 2 , 4 atm H 2 , 140 °C), with production rates much higher than Ag on alumina and even comparable to the state-of-the-art Ru on alumina catalyst (Ru–Al 2 O 3 ) under these reaction conditions, according to literature results.

The direct utilization of metals from electronic waste (e‐waste) in catalysis is a barely explored concept that, however, should be feasible for reactions where the catalytically active species can be formed in situ from the e‐waste metal pieces. This approach circumvents any capture or isolation of particular metals, thus saving additional treatments (extractions, neutralization, separations, washings, …) and valorizing the e‐waste in its own. Here, it is shown that a metallic contact (≈1 mg) of a computer´s random‐access memory (RAM) catalyzes a variety of organic reactions in high yields. For instance, one RAM contact catalyzes the one‐pot esterification‐hydration reaction between acyl chlorides, propargyl alcohols, and water, at room temperature in 93–99% yields with turnover frequencies >0.5 million per hour. In this way, >50 kg of organic products could be prepared with just the RAM contacts discarded per year in the Institute´s recycling bin. These results open the way to directly use e‐waste in catalysis for organic synthesis. Wasted RAM contacts catalyze different organic reactions in good to excellent yields, with turnover numbers >0.5 million in some cases. The RAM contacts are used without any previous treatment and are recovered and reused. Kilograms of organic products could be produced with the RAM contacts of just five discarded laptops. These results open the way to use directly e‐waste in catalysis for organic synthesis.

Metal individual atoms and few-atom clusters show extraordinary catalytic properties for a variety of organic reactions, however, their implementation in total synthesis of complex organic molecules is still to be determined. Here we show a 11-step linear synthesis of the natural product (±)-Licarin B, where individual Pd atoms (Pd 1 ) catalyze the direct aerobic oxidation of an alcohol to the carboxylic acid (steps 1 and 6), Cu 2-7 clusters catalyze carbon-oxygen cross couplings (steps 3 and 8), Pd 3-4 clusters catalyze a Sonogashira coupling (step 4) and Pt 3-5 clusters catalyze a Markovnikov hydrosylilation of alkynes (step 5), as key reactions during the synthetic route. In addition, the new synthesis of Licarin B showcases an unexpected selective alkene hydrogenation with metal-free NaBH 4 and an acid-catalyzed intermolecular carbonyl-olefin metathesis as the last step, to forge a trans -alkene group. These results, together, open new avenues in the use of metal individual atoms and clusters in organic synthesis, and confirm their exceptional catalytic activity in late stages during complex synthetic programmes. Individual metal atoms and few-atom metal clusters have shown promising catalytic activities, however, their exploitation in the total synthesis of complex organic molecules remains underexplored. Here, the authors develop a total synthesis of the bioactive natural product (±)-Licarin B involving key steps catalyzed by soluble individual Pd atoms and Cu/Pd/Pt clusters, achieving an 11-step linear synthesis and overall yield of 13.1%.

The development of catalysts able to assist industrially important chemical processes is a topic of high importance. In view of the catalytic capabilities of small metal clusters, research efforts are being focused on the synthesis of novel catalysts bearing such active sites. Here we report a heterogeneous catalyst consisting of Pd 4 clusters with mixed-valence 0/+1 oxidation states, stabilized and homogeneously organized within the walls of a metal–organic framework (MOF). The resulting solid catalyst outperforms state-of-the-art metal catalysts in carbene-mediated reactions of diazoacetates, with high yields (>90%) and turnover numbers (up to 100,000). In addition, the MOF-supported Pd 4 clusters retain their catalytic activity in repeated batch and flow reactions (>20 cycles). Our findings demonstrate how this synthetic approach may now instruct the future design of heterogeneous catalysts with advantageous reaction capabilities for other important processes. Mixed-valence clusters of Pd 4 organized within a metal–organic framework exhibit robust catalytic capacities during carbene-mediated chemical reactions.

The removal of acetylene from ethylene streams is key in industry for manufacturing polyethylene. Here we show that a well-defined Pd 1 –Au 1 dimer, anchored to the walls of a metal–organic framework (MOF), catalyses the selective semihydrogenation of acetylene to ethylene with ≥99.99% conversion (≤1 ppm of acetylene) and >90% selectivity in extremely rich ethylene streams (1% acetylene, 89% ethylene, 10% H 2 , simulated industrial front-end reaction conditions). The reaction proceeds with an apparent activation energy of ∼1 kcal mol –1 , working even at 35 °C, and with operational windows (>100 °C) and weight hourly space velocities ( 66 , 000 ml g cat − 1 h − 1 ) within industrial specifications. A combined experimental and computational mechanistic study shows the cooperativity between both atoms, and between atoms and support, to enable the barrierless semihydrogenation of acetylene. The semihydrogenation of acetylene is an important industrial reaction generally targeted with alloy catalysts and more recently with single-atom catalysts. Here, the authors report a MOF-supported Pd 1 –Au 1 dimeric system that, by merging such approaches, results in high performance levels under simulated front-end industrial conditions.

The oxidative addition–reductive elimination (OARE) mechanism of reactive molecules on metal atoms is a cornerstone of modern chemistry. However, the complementary reductive addition–oxidative elimination (RAOE) mechanism is barely considered, despite a first reduction reaction between metal atoms and the incoming organic reactant makes chemical sense in a plethora of processes. Here we show, in a chronological order, early precedents in the literature which indicated the possibility of a general RAOE mechanism, the few systems explicitly reported so far (including a catalytic system) and some other reactions where a RAOE mechanism would satisfactorily explain the mechanistic evidences found. These examples, together, strongly suggest that researchers should consider the RAOE mechanism during their investigations, and not simply adjust their conclusions to the omnipresent OARE mechanism. This new line of thinking might open new avenues in the design of chemical reactions, particularly catalytic ones. The reductive addition–oxidative elimination (RAOE) mechanism is proposed here as an alternative to the omnipresent oxidative addition–reductive elimination (OARE) mechanism. Opposite to the latter, the RAOE mechanism occurs over reducible rather than oxidable metal species, enabling different pathways in catalysis, materials design and organic synthesis.

The benzyl cation is an iconic intermediate in organic chemistry which has not been isolated yet. Here, we show that the incorporation of tropylium cations in commercially available sodium zeolites, after cation exchange, plausibly triggers the spontaneous formation of benzyl cations inside the zeolite pores at room temperature. The zeolite plays a bifunctional role as a host. First, the unimolecular rearrangement reaction occurs by the ability of the zeolite to isolate tropylium molecules and achieve the required energy to transform tropylium into benzyl cations. Then, the compartmentalized nature of the zeolite framework avoids the quenching of the so–formed benzyl cations with each other, or any other nucleophile, allowing lifetimes of weeks for the benzyl cations under ambient conditions. In this way, a customary organic characterization of the zeolite–embedded benzyl cation by absorption ultraviolet–visible spectrophotometry and 13C nuclear magnetic resonance (13C NMR) has now been possible. Transient absorption spectroscopy and reactivity studies, together with molecular dynamic calculations, further support the formation of the benzyl cation inside the zeolite. These results bring this fundamental carbocation intermediate to our laboratories as a manageable organic compound. The benzyl cation is plausibly formed inside zeolites after rearrangement of individually isolated tropylium cations at room temperature. The benzyl cation–entrapped zeolite is stable for weeks without any storage precaution, and a solid–state 13C nuclear magnetic resonance spectrum of this iconic carbocation could be recorded.