Supramolecular porphyrin assemblies through amidinium-carboxylate salt bridges and fast intra-ensemble excited energy transfer

Well‐defined supramolecular assemblies of Zn and free‐base porphyrins are constructed through the formation of amidinium–carboxylate salt bridges. A one‐to‐one donor–acceptor pair and a four‐to‐one antenna‐type assembly are investigated. The steady‐state and time‐resolved fluorescence measurements unequivocally showed that efficient singlet–singlet excited energy transfer from the Zn–porphyrin complex to the free‐base porphyrin takes place in these assemblies. Indeed, the observed energy‐transfer rates in both types of assemblies are much faster than those the Förster mechanism would suggest, implying the involvement of an intermolecular through‐bond mechanism.     

Palladium-catalyzed nucleophilic benzylic substitutions of benzylic esters

A palladium complex generated in situ from [Pd(eta3-C3H5)(cod)]BF4 and DPPF is a good catalyst for benzylic alkylation of benzyl methyl carbonate with the carbanion of dimethyl malonates. The catalytic reaction is applicable to a wide range of the benzylations of benzylic esters with malonates. The catalytic activity was heavily affected by the bite angle of the bidentate phosphine ligand on palladium. DPEphos ligand is superior to DPPF in the case of palladium-catalyzed benzylic amination of benzylic esters.     

[IrCl(cod)]2-catalyzed direct oxidative esterification of aldehydes with alcohols

[IrCl(cod)]₂ catalyzed the oxidative esterification of a variety of aldehydes with methanol as a solvent in combination with K₂CO₃ under mild conditions (rt, 12 h). The oxidative esterification reaction of aliphatic aldehydes also took place with olefinic alcohols as reagents in toluene under similar conditions.     

Efficient oxidation of alcohols electrochemically mediated by azabicyclo-N-oxyls

Preparation of azabicyclo-N-oxyls and the electrochemical oxidation of alcohols using them as mediators have been exploited. This oxidation was applicable to a transformation of sterically hindered secondary alcohols into the corresponding ketones in high yields.     

Effective procedure for selective ammonolysis of monosubstituted oxiranes: application to E7389 synthesis

A highly effective procedure is reported to synthesize 1,2-aminoalcohols by regio- and chemo-selective ammonolysis of mono-substituted epoxides. Additive- and concentration-effects were studied, revealing that (1) methanesulfonic acid is most effective among the additives tested and (2) formation of bis-adducts is practically eliminated at [C] ? 40 mM. The optimum condition thus identified was successfully applied to the final step of the synthesis of potent anti-tumor compound E7389.     

Stabilization effects of carboxylate on pyrotechnic compositions including Mg powder in water

Magnesium powder is a common fuel in the field of pyrotechnics. The metal corrodes easily under wet conditions. This can lead to problems such as spontaneous ignition and deterioration of combustion performance when the powder is used in humid areas. For pyrotechnic compositions containing magnesium, harmful stabilizers are often used. In this study, we researched a less harmful replacement for the stabilizer and selected linseed oil, which is used as cooking oil. Experiments were conducted to examine linseed oil’s stabilization effects against magnesium corrosion when it is in contact with an oxidizer under humid conditions by coating magnesium powder and soaking it in aqueous oxidizer solutions. The oxidation of linseed oil led to its polymerization, because of which the stabilizing effect of linseed oil was lost. Stearic acid, which is a saturated fatty acid, was also examined for its stabilizing effects. Melted stearic acid was mixed with magnesium, and coating of stearic acid on magnesium particles was confirmed. The effect of stearic acid coating is more prominent than that of simple mixing of stearic acid with Mg. The stabilization effect of linseed oil and stearic acid coating shows that unharmful organic stabilizers can also be used in pyrotechnic compositions containing Mg.

     

Cupin Variants as a Macromolecular Ligand Library for Stereoselective Michael Addition of Nitroalkanes

Cupin superfamily proteins (TM1459) work as a macromolecular ligand framework with a double‐stranded β‐barrel structure ligating to a Cu ion through histidine side chains. Variegating the first coordination sphere of TM1459 revealed that H52A and H54A/H58A mutants effectively catalyzed the diastereo‐ and enantioselective Michael addition reaction of nitroalkanes to an α,β‐unsaturated ketone. Moreover, calculated substrate docking signified C106N and F104W single‐point mutations, which inverted the diastereoselectivity of H52A and further improved the stereoselectivity of H54A/H58A, respectively.