Acid effects on the chemical properties of metal−oxygen intermediates have attracted much attention recently, such as the enhanced reactivity of high-valent metal(IV)−oxo species by binding proton(s) or Lewis acidic metal ion(s) in redox reactions. Herein, we report for the first time the proton effects of an iron(V)−oxo complex bearing a negatively charged tetraamido macrocyclic ligand (TAML) in oxygen atom transfer (OAT) and electron-transfer (ET) reactions. First, we synthesized and characterized a mononuclear nonheme Fe(V)−oxo TAML complex (1) and its protonated iron(V)−oxo complexes binding two and three protons, which are denoted as 2 and 3, respectively. The protons were found to bind to the TAML ligand of the Fe(V)−oxo species based on spectroscopic characterization, such as resonance Raman, extended X-ray absorption fine structure (EXAFS), and electron paramagnetic resonance (EPR) measurements, along with density functional theory (DFT) calculations. The two-protons binding constant of 1 to produce 2 and the third protonation constant of 2 to produce 3 were determined to be 8.0(7) × 10 8 M −2 and 10(1) M −1 , respectively. The reactivities of the proton-bound iron(V)−oxo complexes were investigated in OAT and ET reactions, showing a dramatic increase in the rate of sulfoxidation of thioanisole derivatives, such as 10 7 times increase in reactivity when the oxidation of p-CN-thioanisole by 1 was performed in the presence of HOTf (i.e., 200 mM).The one-electron reduction potential of 2 (E red vs SCE = 0.97 V) was significantly shifted to the positive direction, compared to that of 1 (E red vs SCE = 0.33 V). Upon further addition of a proton to a solution of 2, a more positive shift of the E red value was observed with a slope of 47 mV/log ([HOTf]). The sulfoxidation of thioanisole derivatives by 2 was shown to proceed via ET from thioanisoles to 2 or direct OAT from 2 to thioanisoles, depending on the ET driving force.

3-Hydroxy-2-(trialkylsilyl)phenyl triflates are presented as new versatile hydroxyaryne precursors. These are base-activated aryne precursors induced via a C-sp-to-O 1,3-Brook rearrangement. The reaction of various arynophiles and 3-trialkylsiloxybenzyne generated from 3-hydroxy-2-(trialkylsilyl)phenyl triflate efficiently afforded highly regioselective phenol derivatives. Furthermore, through crossover experiments, the intramolecular mechanism of silyl migration was demonstrated.

A new and mild synthetic approach has been developed for the synthesis of pharmaceutically important unsymmetrical diarylpyridines via chemoselective Suzuki–Miyaura coupling reactions of bromo-2-sulfonyloxypyridines. Most reactions allow for facile access to aryl-2-sulfonyloxypyridines at room temperature in yields of 5–99% with excellent chemoselectivity in the presence of Pd­(OAc)2 (2.0 mol %) and Ad2BnP (2.4 mol %). The second arylation of the remaining tosyl or triflyl group in the monoarylpyridine derivatives obtained was successfully accomplished for the synthesis of unsymmetrical 2,3-, 2,4-, 2,5-, and 2,6-diarylpyridine derivatives. Furthermore, a one-pot synthesis of unsymmetrical diarylpyridines starting from bromo-2-sulfonyloxypyridine was accomplished to demonstrate the practical convenience. Finally, with this method, an antibacterial agent, a topoisomerase inhibitor, and etoricoxib, a nonsteroidal anti-inflammatory drug, were successfully synthesized from the corresponding bromo-2-hydroxypyridines in overall yields of 80, 86, and 49%, respectively.

The design, synthesis, and validation of 3-aminobenzyne precursors induced by C-(sp2)-to-N 1,3-aza-Brook rearrangement have been achieved, allowing access to diverse aniline derivatives. Through crossover experiments, we demonstrated the intramolecular mechanism of 1,3-C-to-N silyl transfer. To gain insight into the regioselectivity observed in the reactions, we performed density functional theory calculations. Finally, the method was applied to the synthesis of xylanigripones A in five linear steps in an overall yield of 30%.

the interface between an electrode and a photoactive layer, an interfacial layer that is capable of selectively transporting electrons or holes is required. [6][7][8][9][10][11][12] Generally, transition metal oxides such as zinc oxide (ZnO), [13] titanium dioxide (TiO 2 or TiO x ) [14] and tin oxide (SnO 2 or SnO x ) [15] are used as interlayer materials because of their optical transparency, high electron mobilities, and chemical stability. [16] Usually, these interlayer materials are deposited using vacuum deposition techniques such as atomic layer deposition, electronbeam deposition, and sputtering. [17][18][19][20][21] However, these vacuum deposition techniques can damage the organic materials in the photoactive layers.To overcome this limitation, solution processing of interfacial layers has been introduced because of its advantages over the vacuum processes, such as less destructive fabrication, large-area manufacturing, low costs, and a high output production. [22][23][24][25][26] However, solution processes mostly involve sintering for hydrolyzing the metal oxide precursors, and sintering requires high temperatures that affect the morphological and chemical stability of the organic photoactive layers. [27,28] In addition, the sintering temperatures are usually higher than the glass temperature of plastic substrates, resulting in a limited substrate selection. Therefore, it is necessary to develop a solution processable transition metal oxide nanoparticle that does not require a high-temperature hydrolysis process. [22,[29][30][31][32][33][34][35] One method is to synthesize highly dispersive metal nanoparticles in an organic solvent, and then coating these nanoparticles directly onto the photoactive layer. [36][37][38] Recently, we reported the preparation of highly dispersive titanium oxide (TiO 2 ) nanoparticles (TNPs) by bounding TiO 2 with organic ligands. [31,39] We found that combining the TNPs with an organic ligand containing a phenyl group stabilized the surface of the TNPs and formed a robust electron transporting layer (ETL), because of the strong π-π interactions between the particles. These TNPs were well dispersed in organic solvents, easily spin-coated onto a photoactive layer at room temperature and utilized as efficient ETLs in OPVs. For organic photovoltaics (OPVs), the electron transport layer (ETL) material is crucial for collecting and transporting the electrons from the active material toward the electrode. In this study, TiO 2 nanoparticles (TNPs) are functionalized with a series of catechol (CA) derivatives possessing different electrophilicities, i.e., CA; CA attached to an electron-withdrawing cyano group, 3,4-Dihydroxy benzonitrile (CA-CN); and CA attached to an electron-donating methoxy group, 4-Methoxybenzene-1,2-diol (CA-OMe), and the resulting solution-processed films are applied as ETLs. The calculated energy level shows that the lowest unoccupied molecular orbital (LUMO) is lowered by the cyano group and raised by the methoxy group, and it forms different cascade energy ...