Tuning the CO2 Reduction Selectivity of an Immobilized Molecular Ag Complex beyond CO.

The electrochemical reduction of carbon dioxide (CO2) to produce fuels and chemicals has garnered significant attention. However, achieving control over the selectivity of the resulting products remains a challenging task, particularly within molecular systems. In this study, we employed a molecular silver complex immobilized on graphitized mesoporous carbon (GMC) as a catalyst for converting CO2 into CO, achieving an impressive selectivity of over 90% at -1.05 V vs RHE. Notably, the newly formed silver nanoparticles emerged as the active sites responsible for this high CO selectivity rather than the molecular system. Intriguingly, the introduction of copper ions into the restructured Ag-nanoparticle-decorated carbon altered the product selectivity. At -1.1 V vs RHE in 0.1 M KCl, we achieved a high C2 selectivity of 75%. Furthermore, not only the Ag-Cu bimetallic nanoparticle but also the small-sized Ag-Cu nanocluster decorated over GMC was proposed as active sites during catalytic reactions. Our straightforward approach offers valuable insights for fine-tuning the product selectivity of immobilized molecular systems, extending beyond C1 products.

Electrochemical Synthesis of Glycine from Oxalic Acid and Nitrate.

In manufacturing C-N bond-containing compounds, it is an important challenge to alternate the conventional methodologies that utilize reactive substrates, toxic reagents, and organic solvents. In this study, we developed an electrochemical method to synthesize a C-N bond-containing molecule avoiding the use of cyanides and amines by harnessing nitrate (NO3- ) as a nitrogen source in an aqueous electrolyte. In addition, we utilized oxalic acid as a carbon source, which can be obtained from electrochemical conversion of CO2. Thus, our approach can provide a route for the utilization of anthropogenic CO2 and nitrate wastes, which cause serious environmental problems including global warming and eutrophication. Interestingly, the coreduction of oxalic acid and nitrate generated reactive intermediates, which led to C-N bond formation followed by further reduction to an amino acid, namely, glycine. By carefully controlling this multireduction process with a fabricated Cu-Hg electrode, we demonstrated the efficient production of glycine with a faradaic efficiency (F.E.) of up to 43.1 % at -1.4 V vs. Ag/AgCl (current density≈90 mA cm-2 ).

Atroposelective Total Syntheses of Naphthylisoquinoline Alkaloids with (P)-Configuration.

Asymmetric total syntheses of naphthylisoquinoline alkaloids with a (P)-configuration are described. An atroposelective Suzuki-Miyaura reaction between naphthyl pinacol boronate and an aryl iodide bearing an (S)-2-(N-acetylamino)propyl group at the ortho-position using Pd(OAc)2 in the presence of SPhos and Ba(OH)2 provided the (P)-selective biaryl product as the major product without any external chiral sources. This biaryl product was converted into naphthylisoquinoline alkaloids with a (P)-configuration via stereoselective construction of the isoquinoline framework with the appropriate oxidation state and stereochemistry.

Asymmetric Total Syntheses of Naphthylisoquinoline Alkaloids via Atroposelective Coupling Reaction Using Central Chirality as Atroposelectivity-Controlling Group.

We describe the asymmetric total syntheses of naphthylisoquinoline alkaloids. Atroposelective biaryl coupling reaction between naphthyl pinacol boronate and an aryl iodide, bearing (S)-2-aminopropyl group at the ortho-position using the existing central chirality as an atroposelectivity-controlling group, provided the desired biaryl product with high atroposelectivity, without the use of an external chiral source. From the resulting biaryl product, several naphthylisoquinoline alkaloids were prepared via the stereoselective formation of the isoquinoline framework with the appropriate oxidation state and stereochemistry.

Total Synthesis of Phenanthroquinolizidine Alkaloids Using a Building Block Strategy.

A concise and general strategy for the total synthesis of the phenanthroquinolizidine alkaloids has been developed. An iterative Suzuki-Miyaura coupling reaction between the requisite aryl boronic acid, 2-bromo-4,5-dimethoxyphenyl N-methyliminodiacetate (MIDA) boronate derived from boronic acid, and a suitable bromopyridine substrate bearing a homopropargyl alcohol at the 2-position generated the desired ortho-aza-terphenyl compounds. Hydrogenation of the triple bond followed by treatment with methanesulfonyl chloride afforded their corresponding tetrahydroquinolizinium ion intermediates, which were subsequently reacted with NaBH4 to provide the desired hexahydroquinolizine products. A final oxidative electrocyclization reaction gave the target phenanthroquinolizidine natural products. This synthetic approach only requires the use of three chromatographic separations throughout the entire synthesis.

Modular Syntheses of Phenanthroindolizidine Natural Products.

A highly concise strategy for the total synthesis of phenanthroindolizidines was developed. The one-pot iterative Suzuki-Miyaura reaction of aryl boronic acids with ortho-bromoaryl N-methyliminodiacetate (MIDA) boronate followed by a second Suzuki-Miyaura reaction with a suitable pyridyl bromide provided ortho-aza-terphenyls. Subsequent saturation of the triple bond, treatment with mesyl chloride, and reduction of the resulting dihydroindolizidinium ring afforded the hexahydroindolizines. A final vanadium-catalyzed oxidative electrocyclization provided the desired alkaloids in only three column-separation operations.

Synthesis of Optically Pure 3,3'-Disubstituted-1,1'-Bi-6-Methoxy-2-Phenol (BIPhOL) Derivatives via Diastereomeric Resolution.

A new protocol for the enantioselective synthesis of 3,3'-disubstituted-1,1'-bi-6-methoxy-2-phenol (BIPhOL) derivatives is described. Diastereomeric resolution of racemic BIPhOL boronic acid using a boronic acid moiety as a resolving group generated two diastereomers and subsequent Suzuki-Miyaura coupling reaction of the resulting diastereomers with aryl halides provided BIPhOL derivatives without any loss of enantioselectivity. In addition, the absolute stereochemistry of chiral BIPhOL was determined by comparison of the optical rotation with the reported value.