Selective room-temperature hydrogenation of amides to amines and alcohols catalyzed by a ruthenium pincer complex and mechanistic insight

This research was supported by the European Research Council (ERC AdG 692775). D.M. holds the Israel Matz Professorial Chair of Organic Chemistry. S.K. acknowledges the Sustainability and Energy Research Initiative (SAERI) of the Weizmann Institute of Science for a research fellowship. M.R. acknowledges the Zuckerman STEM Leadership Program for a research fellowship.We report a room-temperature protocol for the hydrogenation of various amides to produce amines and alcohols. Compared with most previous reports for this transformation, which use high temperatures (typically, 100–200 °C) and H2 pressures (10–100 bar), this system proceeds under extremely mild conditions (RT, 5–10 bar of H2). The hydrogenation is catalyzed by well-defined ruthenium-PNNH pincer complexes (0.5 mol %) with potential dual modes of metal–ligand cooperation. An unusual Ru-amidate complex was formed and crystallographically characterized. Mechanistic investigations indicate that the room-temperature hydrogenation proceeds predominantly via the Ru–N amido/amine metal–ligand cooperation.Publisher PDFPeer reviewe

Hydrogenative depolymerization of nylons

This research was supported by the European Research Council (ERC AdG 692775). D. M. holds the Israel Matz Professorial Chair of Organic Chemistry. A. K. is thankful to the Planning and Budgeting Committee of Israel and Feinberg Graduate School for a (senior) postdoctoral fellowship. Y.-Q. Z. acknowledges the Sustainability and Energy ResearchInitiative (SAERI) foundation for a research fellowship. Computations were performed using HPC resources from GENCI-CINES (Grant 2019 AP010811227).The widespread crisis of plastic pollution demands discovery of new and sustainable approaches to degrade robust plastics such as nylons. Using a green and sustainable approach based on hydrogenation, in the presence of a ruthenium pincer catalyst at 150 oC and 70 bar H2, we report here the first example of hydrogenative depolymerization of conventional, widely used nylons, and polyamides in general. Un-der the same catalytic conditions, we also demonstrate the hydrogenation of a polyurethane to produce diol, diamine and methanol. Additionally, we demonstrate an example where monomers (and oligomers) obtained from the hydrogenation process can be dehydrogenated back to a poly(oligo)amide of approximately similar molecular weight, thus completing a closed loop cycle for recycling of poly-amides. Based on the experimental and DFT studies, we propose a catalytic cycle for the process that is facilitated by metal-ligand cooperativity. Overall, this unprecedented transformation, albeit at the proof of concept level, offers a new approach towards a cleaner route to recycling nylons.Publisher PDFPeer reviewe

Nuevos datos acerca de los repertorios teatrales en el primer catálogo de «El peregrino en su patria»

En este artículo se muestra cómo los títulos que contienen los repertorios de los autores de comedias presentes en El peregrino en su patria de 1604 están dispuestos según un orden cronológico, aunque con algunos matices y no pocas excepciones. Además, se amplían los repertorios descubiertos por Thornton Wilder y se afina la fecha de composición de varias obras, prestando especial atención a textos que se han perdido, como La perdición de España, La gobernadora, La gran pintora, La bella gitana o La toma de Álora. Finalmente, el presente artículo pretende mostrar de un modo práctico cómo una base de datos digital como el Diccionario biográfico de actores del teatro clásico español (DICAT) puede resultar de gran ayuda a la hora de resolver algunos de los problemas clásicos de la filología en general y del teatro del Siglo de Oro en particular.This paper shows that the plays contained in the repertoire of the autores de comedias which appear in El peregrino en su patria (1604) are organised chronologically, although there are some nuances and exceptions. The article also expands the repertoire discovered by Thornton Wilder and sets the date of composition for some plays, paying special attention to lost texts such as La perdición de España, La gobernadora, La gran pintora, La bella gitana or La toma de Álora. Finally, this paper attempts to show in a practical way that a database such as the Diccionario biográfico de actores del teatro clásico español (DICAT) can be extremely helpful when it comes to dealing with some of the philology's classical problems in general and those of the theatre of the Golden Age in particular

Manganese catalysed hydrogenation of carbamates and urea-derivatives

We report the hydrogenation of carbamates and urea derivatives, two of the most challenging carbonyl compounds to be hydrogenated, catalyzed for the first time by a complex of an earth-abundant metal. The hydrogenation reaction of these CO2-derived compounds, catalyzed by a manganese pincer complex, yields methanol in addition to amine and alcohol, which makes this methodology a sustainable alternative route for the conversion of CO2 to methanol, involving a base-metal catalyst. Moreover, the hydrogenation proceeds under mild pressure (20 bar). Our observations support a hydrogenation mechanism involving the Mn–H complex. A plausible catalytic cycle is proposed based on informative mechanistic experiments

Direct Synthesis of Benzimidazoles by Dehydrogenative Coupling of Aromatic Diamines and Alcohols Catalyzed by Cobalt

Herein, we present the base-metal-catalyzed dehydrogenative coupling of primary alcohols and aromatic diamines to selectively form functionalized 2-substituted benzimidazoles, liberating water and hydrogen gas as the sole byproducts. The reaction is catalyzed by pincer complexes of Earth-abundant cobalt under base-free conditions

Osmium-Mediated C-H and C-C Bond Cleavage of a Phenolic Substrate: p-Quinone Methide and Methylene Arenium Pincer Complexes.

International audienceThe diphosphine 2,4,6-(CH3)3-3,5-(iPr2PCH2)2C6OH (1) reacts with [OsCl2(PPh3)3] in presence of an excess of triethylamine to yield the isomeric para-quinone methide derivatives [Os{4-(CH2)-1-(O)-2,6-(CH3)2-3,5-(iPr2PCH2)2C6}(Cl)(H)(PPh3)] (2 and 3), which differ in the positions of the mutually trans hydride and chloride ligands. Complex 2 reacts with CO to afford the dicarbonyl species [Os{1-(O)-2,4,6-(CH3)3-3,5-(iPr2PCH2)2C6}(Cl)(CO)2] (4), which results from hydride insertion into the quinonic double bond. Protonation of 2 and 3 leads to the formation of the methylene arenium derivative [Os{4-(CH2)-1-(OH)-2,6-(CH3)2-3,5-(iPr2PCH2)2C6}(Cl)(H)(PPh3)][OSO2CF3] (5 a). The diphosphine 1 reacts with [OsCl2(PPh3)3] at 100 °C under H2 to afford [Os{1-(OH)-2,6-(CH3)2-3,5-(iPr2PCH2)2C6}(Cl)(H2)(PPh3)] (6), a PCP pincer complex resulting formally from C(sp2)C(sp3) cleavage of the CCH3 group in 1. CC hydrogenolysis resulting in the same complex is achieved by heating 2 under H2 pressure. Reaction of the diphosphine substrate with [OsCl2(PPh3)3] under H2 at lower temperature allows the observation of a methylene arenium derivative resulting from CH activation, [Os{4-(CH2)-1-(OH)-2,6-(CH3)2-3,5-(iPr2PCH2)2C6}(Cl)2(H)] (7). This compound reacts with PPh3 in toluene to afford the ionic derivative [Os{4-(CH2)-1-(OH)-2,6-(CH3)2-3,5-(iPr2PCH2)2C6}(Cl)(H)(PPh3)]Cl (5 b). X-ray diffraction studies have been carried out on compounds 2, 3, 4, 5 b, 6, and 7, which allows the study of the structural variations when going from methylene arenium to quinone methide derivatives

Oxidant-Free Conversion of Cyclic Amines to Lactams and H₂ Using Water As the Oxygen Atom Source

Direct conversion of cyclic amines to lactams utilizing water as the only reagent is catalyzed by pincer complex <b>2</b>. In contrast to previously known methods of amine-to-amide conversion, this reaction occurs in the absence of oxidants and is accompanied by liberation of H₂, with water serving as a source of oxygen atom. Formation of a cyclic hemiaminal intermediate plays a key role in enabling such reactivity. This represents an unprecedented, conceptually new type of amide formation reaction directly from amines and water under oxidant-free conditions