Singly and Doubly Quinoxaline-Fused BIII Subporphyrins

B-Phenyl B^III subporphyrin-α-diones prepared in a three-step reaction sequence from the parent subporphyrin were condensed with 1,2-diaminobenzenes to give the corresponding quinoxaline-fused subporphyrins in variable yields. Quinoxaline-fused B-phenyl-5,10,15-triphenyl B^III subporphyrin was transformed to the corresponding subporphyrin-α-dione in the same three-step reaction sequence, which was then condensed with 1,2-diaminobenzene to give doubly quinoxaline-fused subporphyrin. These quinoxaline-fused subporphyrins exhibit redshifted absorption and fluorescence spectra compared with the parent one. A singly quinoxaline-fused subporphyrin bearing three meso-bis(4-dimethylaminophenyl)aminophenyl substituents shows blueshifted fluorescence in less polar solvent, which has been ascribed to emission associated with charge recombination of intramolecular charge transfer (CT) state.     

Stereo-controlled anti-hydromagnesiation of aryl alkynes by magnesium hydrides

A concise protocol for anti-hydromagnesiation of aryl alkynes was established using 1 : 1 molar combination of sodium hydride (NaH) and magnesium iodide (MgI₂) without the aid of any transition metal catalysts. The resulting alkenylmagnesium intermediates could be trapped with a series of electrophiles, thus providing facile accesses to stereochemically well-defined functionalized alkenes. Mechanistic studies by experimental and theoretical approaches imply that polar hydride addition from magnesium hydride (MgH₂) is responsible for the process.

Anti-hydromagnesiation of aryl alkynes was facilitated solely by magnesium hydride. The resulting alkenylmagnesium intermediates were functionalized with various electrophiles to afford stereochemically defined tri-substituted alkenes.     

Fluorescence Response and Self-Assembly of a Tweezer-Type Synthetic Receptor Triggered by Complexation with Heme and Its Catabolites

There is increasing interest in the development and applications of synthetic receptors that recognize target biomolecules in aqueous media. We have developed a new tweezer-type synthetic receptor that gives a significant fluorescence response upon complexation with heme in aqueous solution at pH 7.4. The synthetic receptor consists of a tweezer-type heme recognition site and sulfo-Cy5 as a hydrophilic fluorophore. The receptor–heme complex exhibits a supramolecular amphiphilic character that facilitates the formation of self-assembled aggregates, and both the tweezer moiety and the sulfo-Cy5 moiety are important for this property. The synthetic receptor also exhibits significant fluorescence responses to biliverdin and bilirubin, but shows very weak fluorescence responses to flavin mononucleotide, folic acid, and nicotinamide adenine dinucleotide, which contain smaller π-scaffolds.     

Oxygen ion conductivity of yttria-niobia mixed oxide with fluoride related structure

The oxygen ion conductivity of Y₂O₃---Nb₂O₅ with a fluorite-like structure was studied. Substitutional solid solutions of Nb₂ O₅ in Y₂O₃ lattice formed the defect fluorite phase and remarkably enhanced the oxygen ion conductivity. Doping with tetravalent cations, especially Ti⁴⁺ or Ce⁴⁺, in yttria-niobia oxide is effective in enhancing the oxygen ion conductivity. Although the n-type semiconducting property appeared below P_O2 = 10⁻¹⁸ atm at 1243 K, the yttria-niobia mixed oxide doped with Ce⁴⁺, Ti⁴⁺, and Zr⁴⁺ stably exhibited oxygen-ion conduction in the wide range of oxygen partial pressures studied.     

Fluctuating Carbonaceous Networks with a Persistent Molecular Shape: A Saddle‐Shaped Geodesic Framework of 1,3,5‐Trisubstituted Benzene (Phenine)

A saddle‐shaped macromolecule has been synthesized. The molecule was designed as a geodesic saddle with 1,3,5‐trisubstituted benzene (named phenine) as the fundamental unit. The phenines were woven into a polygonal framework that was composed of 168 sp²‐hybridized carbon atoms. The saddle‐shaped structure with unique symmetry showed atypical conformational changes. The biaryl linkages in this molecule had a small energy barrier for rotation, and these structural fluctuations resulted in seven ¹H NMR resonances representing 84 aromatic hydrogen atoms. Nevertheless, the overall saddle shape of the molecule was persistent, and the “up” and “down” orientations of phenine moieties circulated to give average ¹H resonances. The structural characteristics of this molecule, including the anomalous entropy‐driven dimerization, may deepen our understanding of defect‐rich graphitic sheets.     

One‐pot Annulation for Biaryl‐fused Monocarba‐closo‐dodecaborate through Aromatic B−H Bond Disconnection

We have developed a one‐pot annulation reaction of monocarba‐closo‐dodecaborate with cyclic diaryliodonium salts to afford biaryl‐fused derivatives. Aryl functionalities are introduced at both the 1‐carbon and unreactive ortho‐boron vertices of the “σ‐aromatic” carborane cage without the need for pre‐functionalization. DFT calculations revealed that the palladium‐catalyzed C?B bond‐formation step in this process proceeds through a concerted metalation–deprotonation (CMD)‐type pathway for the B?H bond disconnection on the aromatic cage, though such bonds are generally regarded as hydridic.     

Synthesis of dl-coriolin

The total synthesis of dl-coriolin has been achieved in a stereoselective way. The key tricyclic intermediate was synthesized from dicyclopentadiene through a route which involved an S_N2 reaction at a neopentylic position.