Recent advances in diphosphination of alkynes and alkenes

1,2-Bis(diphenylphosphino)ethenes and -ethanes (DPPEs) are among representative supporting ligands in transition metal catalysts, which can promote otherwise challenging organic transformations with high efficiency and selectivity. Such bidentately coordinating ligands are conventionally prepared by nucleophilic substitution reactions of halogenated carbon electrophiles with nucleophilic metal phosphides. However, they suffer from poor functional group compatibility and/or tedious preparation of highly functionalized starting substrates. In this context, additions of phosphines to readily available and simple alkynes and alkenes have recently received significant attention. This digest paper focuses on recent developments of diphosphination of alkynes and alkenes for the synthesis of DPPE-type ligands. The reported approaches are categorized into several types of reactions, and their scope, limitation, and mechanism are briefly summarized.     

Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

Arene‐fused cyclooctatetraenes (COTs) possess unique structural and electronic properties that originate from their saddle‐shaped π‐conjugated architectures. Considerable attention has been paid to the transition‐metal‐mediated synthesis of these cyclic compounds; however, there have been limited achievements to date in the efficient construction of heteroarene‐fused COTs. In this contribution, we report a novel Pd‐catalyzed dehydrogenative cyclodimerization of biheteroarenes through four‐fold C−H activation toward the synthesis of a series of heteroarene‐fused COTs. A set of mechanistic investigations indicated the involvement of high‐valent Pd species prior to the dimerization event in the catalytic cycle. The redox behavior of the obtained COTs is also described briefly.     

VOLATILITY AND SOLUBILIZATION OF SYNTHETIC FRAGRANCES BY PLURONIC P-85

The volatility of synthetic fragrances (benzyl formate, benzyl acetate, benzyl propionate) from pluronic P-85 aqueous solution has been investigated by the dynamic headspace method The experimental results showed that the volatility of a more hydrophobic fragrance was strongly controlled by pluronic P-85. This volatile behavior was explained by the solubilization constants of fragrances between the micelle and bulk phase by semiequilibrium dialysis method.     

Synthesis and luminescence properties of biphenyl-type firefly luciferin analogs with a new,near-infrared light-emitting bioluminophore

New firefly luciferin analogs of the 4,4′-substituted biphenyl-type were synthesized. One analog with a 4′-dimethylamino group possessed bioluminescence activity, emitting near-infrared biological window light at 675 nm suitable for deep-site bioimaging of living animals. The chemiluminescence light-emission maximum of the corresponding methyl ester of the bioluminescence active analog was 500 nm, implying that biphenyl and thiazolinone rings in the light emitter might be placed in a coplanar conformation at the polar luciferase active site.     

Low-light image enhancement based on soft-closing-based illumination estimation and noise mitigation using correlation among RGB components

Optical Review - Many low-light image enhancement methods have been proposed so far. LIME by Guo et al. (IEEE Trans. Image Process. 26(2):982–993 (2017)) is one of the sophisticated...     

Stereoselective synthesis of malyngic acid and fulgidic acid

A new stereoselective total synthesis of malyngic acid has been achieved from a known oxazolidinone derivative via eight steps involving the Evans asymmetric alkylation as the chirality-inducing step and chelation-controlled Zn(BH₄)₂ reduction of an α-hydroxy ketone intermediate for the installation of the 12,13-anti stereochemistry. Fulgidic acid, the C12-epimer of malyngic acid, has also been synthesized in eight steps from the same starting material by using syn-selective K-Selectride reduction of an α-alkoxy ketone intermediate.     

Nickel-catalyzed synthesis of 1,3,5-trisubstituted hydantoins from acrylates and isocyanates

One molecule of acrylate reacts with two molecules of isocyanate in the presence of a nickel(0)/SIPr catalyst to give a 1,3,5-trisubstituted hydantoin. Two processes operate in sequence, the first, regioselective formation of N-substituted fumaramate from acrylate and isocyanate and, the second, ring closure of the fumaramate with incorporation of another molecule of isocyanate.     

Dialkylaluminum hydride-promoted cyclodimerization of silylated 1,3-enynes via skeletal rearrangement

The dialkylaluminum hydride-promoted reaction of 1-silylalk-3-en-1-ynes gave symmetrical 1,2,3,5-tetrasubstituted benzenes as single regioisomers. The novel cyclodimerization via skeletal rearrangement can be rationalized by an unprecedented mechanism involving sequential hydroalumination, alkene isomerization, carboalumination, carbon-carbon bond cleavage, and retro-hydroalumination.     

Simultaneous concentration enrichment and electrophoretic separation of weak acids on a microchip, using in situ photopolymerized carboxylate-type polyacrylamide gels as the permselective preconcentrator

A method for the simultaneous concentration and separation of weak acids using an acidic polyacrylamide gel, fabricated in the microfluidic channel of a commercial poly(methyl methacrylate)-made microchip, is reported. This approach is based on simple photochemical copolymerization for the fabrication of a permselective preconcentrator. The intersection of the poly(methyl methacrylate)-made microchip was filled with a gel solution comprising acrylamide, N,N'-methylene-bis-acrylamide, and 2-acrylamidoglycolic acid, with riboflavin as a photocatalytic initiator. In situ polymerization, near the cross of the sample outlet channel, was performed by irradiation with an argon ion laser beam that is also used as the light source for fluorimetric detection. The electrokinetic properties, combined with electrostatic repulsion between sample components and the anionic groups on the polyacrylamide gel, enable the entrapment and concentration of weak acids at the interface of the cathodic side of the gel plug. This method displays concentration factors of up to 10(5) within 3 min. The effectiveness of the ionic preconcentrator was demonstrated by the sensitive analysis of fluorescein isothiocyanate-labeled amino acids.