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Herein, we report a mild and general protocol for chemoselective deacetylation of mixed acetyl- and benzoyl-protected carbohydrates under mild acidic conditions. The protocol allows quick access to partially protected carbohydrates, which serve as versatile synthetic intermediates during the total synthesis of various mono- and oligosaccharide targets. The applicability of the developed protocol was successfully demonstrated on a range of carbohydrate substrates of various configurations and substitution patterns featuring functionalized aliphatic and aromatic aglycones. The protocol has shown excellent compatibility with the widely used O-anomeric protecting groups, prespacer aglycones, and thioglycoside glycosyl donors.

A silver-catalyzed protocol for the intermolecular radical umpolung cross-coupling protocol of silyl enol ethers with activated methylene compounds is disclosed. The protocol exhibits excellent functional group tolerance, enabling the expedient preparation of a variety of tricarbonyl compounds. Preliminary mechanistic investigations suggest that the reaction proceeds through a process involving free radicals in which silver oxide has a dual role, acting as both a catalyst and a base.

Herein, a straightforward synthetic approach for the construction of phenanthridin-6(5H)-one skeletons is disclosed. The developed protocol relies on palladium catalysis, providing controlled access to a range of functionalized phenanthridin-6(5H)-ones in 59–88% yields. Furthermore, plausible reaction pathways are proposed based on mechanistic experiments.

A protocol for a tandem Pd/Cu-catalyzed intermolecular cross-coupling cascade between o-bromobenzoic acids and 2-(2-bromoaryl)-1H-benzo[d]imidazoles or the corresponding imidazoles is presented. The protocol provides conceptually novel and controlled access to synthetically useful N-fused (benzo)imidazophenanthridine scaffolds with high efficiency, a broad substrate scope, and excellent functional group compatibility.

A protocol for silver-catalyzed controlled intermolecular cross-coupling of silyl enolates is disclosed. The protocol displays good functional group tolerance and allows efficient preparation of a series of synthetically useful 1,4-diketones. Preliminary mechanistic investigations suggest that the reaction proceeds through a one-electron process involving free radical species in which PhBr acts as the oxidant.

An unprecedented silver-promoted regioselective (4 + 1) annulation of isocyanoacetates with pyridinium salts is reported. The established protocol provides controlled, facile, and modular access to a range of synthetically useful N-fused heterocyclic scaffolds containing indolizines, pyrrolo[1,2-a]quinolines, pyrrolo[2,1-a]isoquinolines, and 1H-imidazo[4,5-a]indolizin-2(3H)-ones. A mechanistic pathway involving nucleophilic addition/protonation/elimination/cycloisomerization is proposed.

Fossil fuel shortage and severe climate changes due to global warming have prompted extensive research on carbon-neutral and renewable energy resources. Hydrogen gas (H2), a clean and high energy density fuel, has emerged as a potential solution for both fulfilling energy demands and diminishing the emission of greenhouse gases. Currently, water oxidation (WO) constitutes the bottleneck in the overall process of producing H2from water. As a result, the design of efficient catalysts for WO has become an intensively pursued area of research in recent years. Among all the molecular catalysts reported to date, ruthenium-based catalysts have attracted particular attention due to their robust nature and higher activity compared to catalysts based on other transition metals.

Herein is reported the first total synthesis of benzyl salicylate and benzyl gentisate glucosides present in various plant species, in particular the Salixgenus, such as Populus balsamiferaand P. trichocarpa. The method permits the synthesis of several natural phenolic acid derivatives and their glucosides starting from salicylic or gentisic acid. The divergent approach afforded access to three different acetylated glucosides from a common synthetic intermediate. The key step in the total synthesis of naturally occurring glycosides—the selective deacetylation of the sugar moiety—was achieved in the presence of a labile benzyl ester group by employing mild deacetylation conditions. The protocol permitted synthesis of trichocarpine (4 steps, 40% overall yield), isotrichocarpine (3 steps, 51% overall yield), trichoside (6 steps, 40% overall yield), and deoxytrichocarpine (3 steps, 42% overall yield) for the first time (>95% purity). Also, the optimized mild deacetylation conditions allowed synthesis of 2-O-acetylated derivatives of all four glycosides (5–17% overall yield, 90–95% purity), which are rare plant metabolites.

Herein, an organocatalytic method for photochemical C–O bond cleavage of lignin systems is reported. The use of photochemistry enabled fragmentation of the β-O-4 linkage, the primary linkage in lignin, provides the fragmentation products in good to high yields. The approach was merged with reported oxidation conditions in a one-pot, two-step platform without any intermediary purification, suggesting its high fidelity. The future utility of the organocatalytic method was illustrated by applying the visible light-mediated protocol to continuous flow processing.

A copper-catalyzed reaction between 2-bromo-benzothioamides and S8or Se involving sulfur rearrangement is reported, enabling access to benzodithioles 2and benzothiaselenoles 6in the presence of Cs2CO3. In the absence of S8or Se, the reaction affords dibenzodithiocines 7via two consecutive C(sp2)–S Ullmann couplings.

A silver-assisted method for [3 + 2] annulation of nitrones with isocyanides has been developed. The developed protocol allows access to a variety of 2,3,4-trisubstituted 1,2,4-oxadiazolidin-5-one derivatives as single diastereomers in good to excellent yields using silver oxide as the catalyst and molecular oxygen as the terminal oxidant. A plausible mechanism involving a nucleophilic addition/cyclization/protodeargentation/oxidation pathway is proposed on the basis of experimental results.

A silver-mediated reaction between 2-ethynyl-3-(1-hydroxyprop-2-yn-1-yl)phenols or 2-ethynyl-3-(1-hydroxyprop-2-yn-1-yl)anilines and methylene isocyanides has been developed. A sequential 5-endo-digcyclization and [3 + 2] cycloaddition process is proposed. This synthetic strategy is atom- and step-efficient and applicable to a broad scope of substrates, allowing the synthesis of valuable substituted benzofuran- and indole-pyrroles in moderate to high yields.

Catalysts for oxidation of water to molecular oxygen are essential in solar-driven water splitting. In order to develop more efficient catalysts for this oxidatively demanding reaction, it is vital to have mechanistic insight in order to understand how the catalysts operate. Herein, we report the mechanistic details associated with the two Ru catalysts 1and 2. Insight into the mechanistic landscape of water oxidation catalyzed by the two single-site Ru catalysts was revealed by the use of a combination of experimental techniques and quantum chemical calculations. On the basis of the obtained results, detailed mechanisms for oxidation of water by complexes 1and 2are proposed. Although the two complexes are structurally related, two deviating mechanistic scenarios are proposed with metal–ligand cooperation being an important feature in both processes. The proposed mechanistic platforms provide insight for the activation of water or related small molecules through nontraditional and previously unexplored routes.

Lignin is a recalcitrant and underexploited natural feedstock for aromatic commodity chemicals, and its degradation generally requires the use of high temperatures and harsh reaction conditions. Herein we present an ambient temperature one-pot process for the controlled oxidation and depolymerization of this potent resource. Harnessing the potential of electrocatalytic oxidation in conjugation with our photocatalytic cleavage methodology, we have developed an operationally simple procedure for selective fragmentation of β-O-4 bonds with excellent mass recovery, which provides a unique opportunity to expand the existing lignin usage from energy source to commodity chemicals and synthetic building block source.

The development of efficient and robust catalysts for H2O oxidation is an essential element in solar water splitting. The reaction mechanism for a previously reported dinuclear Ru water oxidation catalyst (1) has been investigated in detail through quantum chemical calculations. The predicted mechanism starts from a Ru2III,IIIcomplex with two aqua ligands. After three sequential oxidations, O–O bond formation occurs at a formal Ru2IV,Vstate viathe direct coupling of two adjacent oxo moieties while the water nucleophilic attack mechanism was found to be associated with a higher energy barrier. Two H2O molecules are then inserted with subsequent release of O2, which was found to be the rate-limiting step with a barrier of 22.7 kcal mol−1. In a previous work, it was revealed that the ligand scaffold in the studied Ru complex has a non-innocent function. Here, we further highlight this behavior, where the ligand was shown to mediate proton transfer events and accept/donate electrons during the catalytic cycle, which can significantly decrease the redox potentials and facilitate the access to high-valent redox states. This study provides further insight into the H2O oxidation mechanism and principles for designing improved catalysts for activation of small molecules, such as H2O.

Robust catalysts that mediate H2O oxidation are of fundamental importance for the development of novel carbon-neutral energy technologies. Herein we report the synthesis of a group of single-site Ru complexes. Structure–activity studies revealed that the individual steps in the oxidation of H2O depended differently on the electronic properties of the introduced ligand substituents. The mechanistic details associated with these complexes were investigated experimentally along with quantum chemical calculations. It was found that O–O bond formation for the developed Ru complexes proceeds viahigh-valent RuVIspecies, where the capability of accessing this species is derived from the non-innocent ligand architecture. This cooperative catalytic involvement and the ability of accessing RuVIare intriguing and distinguish these Ru catalysts from a majority of previously reported complexes, and might generate unexplored reaction pathways for activation of small molecules such as H2O.

Die Metallzentreneines zweikernigen Mangankatalysators sind an ein zentrales Phenolat, je ein Imidazol sowie an Carboxylate koordiniert – sämtlich wichtige Funktionalitäten des natürlichen Sauerstoff entwickelnden Komplexes. Der Komplex katalysiert die Umwandlung von Wasser in Sauerstoff durch das Einelektronenoxidans [Ru(bpy)3]3+(siehe Bild: bpy=2,2′‐Bipyridin, A=Akzeptor).

Manganificent potential: A dinuclear manganese catalyst contains metal centers that are coordinated by a central phenolate, with adjoining imidazole and carboxylate groups, which are all important functionalities in the natural oxygen‐evolving center. The complex catalyzes the conversion of water to oxygen in the presence of a single‐electron oxidant [Ru(bpy)3]3+(see picture, bpy=2,2′‐bipyridine, A=acceptor).

The new Ru complex 8containing the bio‐inspired ligand 7was successfully synthesized and characterized. Complex 8efficiently catalyzes water oxidation using CeIVand RuIIIas chemical oxidants. More importantly, this complex has a sufficiently low overpotential to utilize ruthenium polypyridyl‐type complexes as photosensitizers.