Development of a Ru-porphyrin-based supramolecular framework catalyst for styrene epoxidation.

A new microporous supramolecular-framework Ru(II)-porphyrin catalyst containing non-covalent interactions between pyrenylphenyl moieties at the -position of the porphyrin ring is synthesised and structurally characterised. This recyclable catalyst expedites styrene epoxidation more efficiently than homogeneous Ru-porphyrin catalytic systems.

Photocatalytic Three-Component Acylcarboxylation of Alkenes with CO.

γ-Keto acid is a valuable chemical motif in a wide range of fields including organic, biological, and medicinal chemistry. However, its single-step synthesis is challenging because of the mismatch of the carbonyl polarity and low tolerance of carboxylic acids. Herein, we report the single-step syntheses of γ-keto acids using alkenes and CO.

Introducing proton/electron mediators enhances the catalytic ability of an iron porphyrin complex for photochemical CO reduction.

A novel iron porphyrin complex with hydroquinone moieties as proton/electron mediators at positions was designed and synthesised. The complex serves as an efficient catalyst for photochemical CO reduction, and its turnover frequency (TOF = 1.3 × 10 h) was the highest among those of comparable systems with sufficient durability.

Visible-Light-Driven Hydroacylation of Unactivated Alkenes Using Readily Available Acyl Donors.

Herein, we report visible-light-driven hydroacylation of unactivated alkenes. We employed benzimidazolines as new acyl donors and achieved perfect regioselectivity, high functional-group tolerance, and excellent substrate generality. We also performed mechanistic experiments to elucidate the detailed reaction mechanism.

Visible light-driven CO reduction with a Ru polypyridyl complex bearing an N-heterocyclic carbene moiety.

A novel Ru polypyridyl complex with an N-heterocyclic carbene ligand was successfully synthesised and characterised. The complex exhibited an intense absorption band in the visible-light region derived from the strong electron-donating character of the carbene ligand, and efficiently catalysed the visible light-driven CO reduction with the reaction rate of 36.7 h.

Photochemical hydrogen production based on the HCOOH/CO cycle promoted by a pentanuclear cobalt complex.

The first catalytic cycle for hydrogen production based on the photochemical two-electron reduction of carbon dioxide (CO) and the dehydrogenation of formic acid at ambient temperature was demonstrated using a pentanuclear cobalt complex (Co5). A series of mechanistic studies were performed to elucidate the mechanism responsible for the promotion of the photocatalytic cycle by Co5.

Photocatalytic redox-neutral hydroxyalkylation of -heteroaromatics with aldehydes.

Hydroxyalkylation of -heteroaromatics with aldehydes was achieved using a binary hybrid catalyst system comprising an acridinium photoredox catalyst and a thiophosphoric acid organocatalyst. The reaction proceeded through the following sequence: (1) photoredox-catalyzed single-electron oxidation of a thiophosphoric acid catalyst to generate a thiyl radical, (2) cleavage of the formyl C-H bond of the aldehyde substrates by a thiyl radical acting as a hydrogen atom transfer catalyst to generate acyl radicals, (3) Minisci-type addition of the resulting acyl radicals to -heteroaromatics, and (4) a spin-center shift, photoredox-catalyzed single-electron reduction, and protonation to produce secondary alcohol products. This metal-free hybrid catalysis proceeded under mild conditions for a wide range of substrates, including isoquinolines, quinolines, and pyridines as -heteroaromatics, as well as both aromatic and aliphatic aldehydes, and tolerated various functional groups.

Effect of metal ion substitution on the catalytic activity of a pentanuclear metal complex.

A pentanuclear cobalt complex that consists of five cobalt ions and six bpp ligands (Co5, Hbpp = 3,5-bis(2-pyridyl)pyrazole) was synthesized and crystallographically characterized. Electrochemical measurements indicate that Co5 has multielectron transfer ability. We also found that Co5 reduces CO to CO under photoirradiation in the presence of a photosensitizer.

One-pot synthesis of cyclic oligosaccharides by the polyglycosylation of monothioglycosides.

Cyclic oligosaccharides such as cyclodextrins (CyDs) have been known as excellent host molecules for the inclusion of various organic guest molecules. The development of new synthetic methods for preparing cyclic oligosaccharides from simple and readily available glycosyl donors would be highly desirable, since the current traditional synthetic routes include multiple reaction steps (glycosylation reactions and deprotections). We herein report on the synthesis of cyclic oligosaccharides by polyglycosylation of monothioglycosides, typically, 2,3,4-protected 1-thioglycosides.

Catalytic Hydrolysis of Phosphate Monoester by Supramolecular Complexes Formed by the Self-Assembly of a Hydrophobic Bis(Zn-cyclen) Complex, Copper, and Barbital Units That Are Functionalized with Amino Acids in a Two-Phase Solvent System.

We previously reported on the preparation of supramolecular complexes by the 2:2:2 assembly of a dinuclear Zn-cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) complex having a 2,2'-bipyridyl linker equipped with 0~2 long alkyl chains (ZnL~ZnL), 5,5-diethylbarbituric acid (Bar) derivatives, and a copper(II) ion (Cu) in aqueous solution and two-phase solvent systems and their phosphatase activities for the hydrolysis of mono(4-nitrophenyl) phosphate (MNP). These supermolecules contain Cu(-OH) core that mimics the active site of alkaline phosphatase (AP), and one of the ethyl groups of the barbital moiety is located in close proximity to the Cu(-OH) core. The generally accepted knowledge that the amino acids around the metal center in the active site of AP play important roles in its hydrolytic activity inspired us to modify the side chain of Bar with various functional groups in an attempt to mimic the active site of AP in the artificial system, especially in two-phase solvent system.

Catalytic Hydrolysis of Phosphate Monoester by Supramolecular Phosphatases Formed from a Monoalkylated Dizinc(II) Complex, Cyclic Diimide Units, and Copper(II) in Two-Phase Solvent System.

Design and synthesis of enzyme mimic with programmed molecular interaction among several building blocks including metal complexes and metal chelators is of intellectual and practical significance. The preparation of artificial enzymes that mimic the natural enzymes such as hydrolases, phosphatases, etc. remains a great challenge in the field of supramolecular chemistry.

Hybrid Catalysis Enabling Room-Temperature Hydrogen Gas Release from N-Heterocycles and Tetrahydronaphthalenes.

Hybrid catalyst systems to achieve acceptorless dehydrogenation of N-heterocycles and tetrahydronaphthalenes-model substrates for liquid organic hydrogen carriers-were developed. A binary hybrid catalysis comprising an acridinium photoredox catalyst and a Pd metal catalyst was effective for the dehydrogenation of N-heterocycles, whereas a ternary hybrid catalysis comprising an acridinium photoredox catalyst, a Pd metal catalyst, and a thiophosphoric imide organocatalyst achieved dehydrogenation of tetrahydronaphthalenes. These hybrid catalyst systems allowed for 2 molar equiv of H gas release from six-membered N-heterocycles and tetrahydronaphthalenes under mild conditions, i.

Catalytic asymmetric synthesis of R207910.

The first asymmetric synthesis of a very promising antituberculosis drug candidate, R207910, was achieved by developing two novel catalytic transformations; a catalytic enantioselective proton migration and a catalytic diastereoselective allylation of an intermediate alpha-chiral ketone. Using 2.5 mol % of a Y-catalyst derived from Y(HMDS)(3) and the new chiral ligand 9, 1.