Effect of initial substrate concentration of the Belousov-Zhabotinsky reaction on self-oscillation for microgel system

Self-oscillation for the microgel particles ( approximately 200 nm in diameter) was studied by changing initial substrate concentrations (i.e., malonic acid, sodium bromate, and nitric acid) of the Belousov-Zhabotinsky (BZ) reaction that is used for chemical energy for the self-oscillation. The cross-linked microgels are composed of N-isopropylacrylamide and ruthenium tris(2,2'-bipyridine), Ru(bpy) 3, which is a catalyst for the BZ reaction. Comparing with the homogeneous, stirred solution of the bulk solution for the BZ reaction, swelling/deswelling oscillation of the microgels showed longer induction period, different dependence of initial substrate concentrations on oscillation period, and different oscillation rhythm. The change in oscillation for the microgels can be understood by considering the microgel network effect.     

Suzuki-Miyaura coupling catalyzed by polymer-incarcerated palladium, a highly active, recoverable, and reusable Pd catalyst

[reaction: see text] Suzuki-Miyaura coupling using a highly efficient and reusable polymer-incarcerated palladium (PI Pd) is described. Various coupling reactions proceeded smoothly using PI Pd with phosphine ligands, and the catalyst could be recovered by simple filtration and reused several times without loss of activity.     

Size‐Selective Complexation and Extraction of Endohedral Metallofullerenes with Cycloparaphenylene

A new strategy for the non‐chromatographic extraction of metallofullerenes from solutions of arc‐processed raw soot is based on the size‐selective complexation with cycloparaphenylene (CPP). [11]CPP has a high affinity for M_x@C₈₂ (x=1, 2); for example, Gd@C₈₂ can be selectively extracted from a fullerene mixture by the addition of [11]CPP. This approach should open new opportunities in metallofullerene chemistry, including for the bulk extraction of metallofullerenes.     

Synthetic studies of GKK1032s: the asymmetric synthesis of the decahydrofluorene skeleton via a novel cyclization of silyl enol ether and sequential retro Diels-Alder and intramolecular Diels-Alder reactions

GKK1032s, which were isolated from the culture broth of Penicillium sp. GKK1032, exhibit antitumor activity. We constructed the fully elaborated decahydrofluorene skeleton of GKK1032s. The C-ring was constructed by intramolecular cyclization reaction between a chiral epoxide and silyl enol ether, and the dienophile moiety was introduced concurrently. In addition, the AB-rings were stereoselectively constructed using novel sequential retro Diels-Alder (DA) and intramolecular Diels-Alder (IMDA) reactions. Several further modifications of the IMDA adduct were carried out, leading to the asymmetric synthesis of the desired hydroxyester including nine stereo centers.     

Single‐Electron‐Transfer‐Induced Coupling of Arylzinc Reagents with Aryl and Alkenyl Halides

Arylzinc reagents, prepared from aryl halides/zinc powder or aryl Grignard reagents/zinc chloride, were found to undergo coupling with aryl and alkenyl halides without the aid of transition‐metal catalysis to give biaryls and styrene derivatives, respectively. In this context, we have already reported the corresponding reaction using aryl Grignard reagents instead of arylzinc reagents. Compared with the Grignard cross‐coupling, the present reaction features high functional‐group tolerance, whereby electrophilic groups such as alkoxycarbonyl and cyano groups are compatible as substituents on both the arylzinc reagents and the aryl halides. Aryl halides receive a single electron and thereby become activated as the corresponding anion radicals, which react with arylzinc reagents, thus leading to the cross‐coupling products.     

Pi-dimer formation in an oligothiophene tweezer molecule

An oligothiophene tweezer molecule, which has two quaterthiophene moieties connected to create an electrochemically activated hinge, has been synthesized. Two-electron oxidation of the tweezer molecule produces an intramolecular pi-dimer between the two oligothiophene moieties at room temperature as confirmed by UV-vis absorption, electrochemistry, and EPR experiments.     

Synthesis of poly(ester-urethane)s from hydroxytelechelic polylactide: Effect of initiators on their physical and degradation properties

A series of poly(l-lactide)-based poly(ester-urethane)s (PEUs) were synthesized by ring-opening polymerization of l-lactide using a variety of diols such as diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TetraEG), 1,5-pentanediol (PD), 1,8-octanediol (OD), isopropyl tartrate (TRAⁱPr) and benzyl tartrate (TRABn) in the presence of Sn(Oct)₂, followed by chain extension with hexamethylene diisocyanate (HMDI). The thermal, mechanical, and degradation properties of the resulting PEUs were studied. The crystallinities of the PEUs decreased with increasing diol contents and were also dependent on the kind of the diol unit. The degradabilities of the PEUs with proteinase K were effectively controlled by the kind of diol unit depending on their size and hydrophilicity. The biodegradation of the PEUs in compost also showed strong dependence on the diol units in the PEUs in spite of relatively low diol content (∼3%).