Influence of Alkoxy Chain Length on the Properties of Two-Dimensionally Expanded Azulene-Core-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells

A series of two-dimensionally expanded azulene-core-based π systems have been synthesized with different alkyl chain lengths in the alkoxy moieties connected to the partially oxygen-bridged triarylamine skeletons. The thermal, photophysical, and electronic properties of each compound were evaluated to determine the influence of the alkyl chain length on their effectiveness as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). All the synthesized molecules showed promising material properties, including high solubility, the formation of flat and amorphous films, and optimal alignment of energy levels with perovskites. In particular, the derivatives with methyl and n-butyl in the side chains retained amorphous stability up to 233 and 159 °C, respectively. Such short alkoxy chains also resulted in improved electrical device properties. The PSC device fabricated with the HTM with n-butyl side chains showed the best performance with a power conversion efficiency of 18.9 %, which compares favorably with that of spiro-OMeTAD-based PSCs (spiro-OMeTAD=2,2′,7,7′-tetrakis[N,N-bis(p-methoxyphenyl)amino]-9,9′-spirobifluorene).     

Enzyme repurposing of a hydrolase as an emergent peroxidase upon metal binding

As an alternative to Darwinian evolution relying on catalytic promiscuity, a protein may acquire auxiliary function upon metal binding, thus providing it with a novel catalytic machinery. Here we show that addition of cupric ions to a 6-phosphogluconolactonase 6-PGLac bearing a putative metal binding site leads to the emergence of peroxidase activity (k_cat 7.8 × 10^–2 s^–1, K_M 1.1 × 10^–5 M). Both X-ray crystallographic and EPR data of the copper-loaded enzyme Cu·6-PGLac reveal a bis-histidine coordination site, located within a shallow binding pocket capable of accommodating the o-dianisidine substrate.     

A novel one-pot reaction involving organocopper-mediated reduction/transmetalation/asymmetric alkylation, leading to the diastereoselective synthesis of functionalized (Z)-fluoroalkene dipeptide isosteres

By a novel one-pot reaction sequence involving consecutive organocopper-mediated reduction, transmetalation and asymmetric alkylation, a highly diastereoselective synthesis of functionalized (Z)-fluoroalkene dipeptide isosteres was achieved in good to excellent yields.     

Potassium carbonate-promoted stereospecific 5-endo-trig cyclization of unactivated allenes in the absence of any transition metals

[STRUCTURE: SEE TEXT] Formation of 3-pyrrolines from simple unactivated allenes bearing a protected amino group under basic conditions is described. Treatment of alpha-amino allenes with potassium carbonate in DMF under reflux in the absence of any transition-metal catalysts gave the corresponding 3-pyrrolines in good to excellent yields, by 5-endo-trig mode cycloisomerization. The reaction of internal allenes with an axial chirality afforded the corresponding 3-pyrrolines in a stereoselective manner.     

Development of a linear type of low molecular weight CXCR4 antagonists based on T140 analogs

A linear type of several low molecular weight CXCR4 antagonists were developed based on T140 analogs, which were previously found to be strong CXCR4 antagonists that block X4-HIV-1 entry and have inhibitory activities against cancer metastasis/progression and rheumatoid arthritis.     

Stereoselective synthesis of separable amide rotamers using π-allyl-Pd catalyst and their thermodynamic behavior

Separable amide rotamers were prepared with moderate to excellent Z-selectivities by N-allylation of 2,4,6-tri-tert-butyl-NH-anilides using a π-allyl-Pd catalyst. The present allylation proceeded through a unique mechanism involving O-allylation and the subsequent O,N-allylic rearrangement. The prepared amide rotamers of Z-major changed to equilibrium mixtures of E-major when heated in toluene.     

Regio- and stereoselective synthesis of (E)-alkene trans-Xaa-Pro dipeptide mimetics utilizing organocopper-mediated anti-S(N)2' reactions

Proline dipeptides (Xaa-Pro) exist as an equilibrium mixture of cis- and trans-rotamers, which depends on the energy barriers for imide isomerization. This conformation mixture contributes to both structure and function of proline-containing peptides and proteins. Structural motifs resembling these cis- or trans-conformers have served as useful tools for elucidating contributions of proline residues in the physicochemical and biological profiles of structures which contain them. Among such motifs are alkene dipeptide isosteres which mimic cis- or trans-imide using (Z)- or (E)-alkene, respectively. In this report, the first regio- and stereoselective syntheses of (E)-alkene dipeptide isosteres (20, 31, and 35) corresponding to trans-proline dipeptides are described. Key to the synthesis of these mimetics is the anti-S(N)2' reaction of vinyl aziridines such as 15 or vinyl oxazolidinones such as 28 and 32 with organocopper reagents "RCu" (R = CH(2)SiMe(2)(Oi-Pr)). Reaction of cis-vinylaziridine 15 derived from L-serine with organocopper reagent gave a precursor of the trans-L-Ser-D-Pro type alkene isosteres 20, accompanied by an S(N)2 side product. One limitation with the use of such aziridine-mediated methodology is formation of the corresponding trans-aziridine 22, which leads to L-L type isosteres, that is unstable and obtainable only in low yield. On the other hand, both isomers of oxazolidinone derivatives can be easily obtained from N-Boc-protected amino alcohols. The reaction of trans- 28 or cis-oxazolidinone derivative 32 with organocopper reagents proceeds quantitatively with high regio- and diastereoselectivities in anti-S(N)2' fashion. Subsequent oxidative treatment of the newly introduced isopropoxydimethylsilylmethyl group yields trans-L-Ser-L-Pro 31 or trans-L-Ser-D-Pro type isosteres 35, respectively. Of note, synthesized isostere 31 can also be converted to trans-phosphoSer-Pro 42 and trans-Cys-Pro mimetics 44. The present synthetic methodology affords trans-Xaa-Pro alkene-type dipeptide isosteres in high yield with relatively simple manipulation.     

Synthesis of allenes from allylic alcohol derivatives bearing a bromine atom using a palladium(0)/diethylzinc system

A general and efficient synthesis of allenes using a palladium(0)/diethylzinc system is described. Treatment of mesylates or trichloroacetates of (E)- or (Z)-2-bromoalk-2-en-1-ols with diethylzinc in the presence of a catalytic amount of palladium(0) affords allenes bearing an aminoalkyl, alkyl, or aryl substituent(s) in good to high yields. No transfer of chirality from the stereogenic center carrying the mesyloxy group to the allene was observed.     

Geochemical Conditions Enhancing the Solubilization of Arsenic into Groundwater in Japan

The geochemical behavior of arsenic-bearing groundwaters from four areas—Fukuoka, Kumamoto, Fukui, and Takatsuki—has been reviewed and considered from the viewpoints of the chemical composition of the water, the geological setting of the host formation, and the arsenic content in sediments and rocks. In all the areas except Fukui, arsenic-bearing water is concluded to have come from a specific aquifer during water–sediment interactions. Stagnant groundwater, having reducing and alkaline properties, played a significant role in the release of arsenic from such Quaternary sediments as silt–clay layers and brownish-colored gravel beds.