A new strategy for construction of angularly fused tricyclic ring systems. Transannular bond formation of bicyclic enones via photochemical intramolecular hydrogen abstraction

Tricyclic ketones 3a, b and 7a–c having angularly fused 5-6-5 or 5-7-5 ring system have been efficiently prepared by irradiation of bicyclic enones 1 and 2.     

Errata

A tunable high power subpicosecond pulse laser with a peak power of more than 1 GW, pulse width of 0.8 ps in the near IR region has been realized. Details of the characteristics of the amplified spontaneous emission and amplification of the laser light in this system are described.     

Novel formation of 1,2-dithiolane-3-thione from β-dithiolactone. Isolation of dithiolato-palladium and -platinum complexes

Sulfurization of β-dithiolactone (4) gave corresponding 1,2-dithiolane-3-thione (2a) via an ionic intermediate. Oxidation of β-dithiolactone 4 by m-CPBA afforded corresponding S-oxide (11), while dioxide (12) was obtained when 3 equiv of m-CPBA was used. Dithiolane-3-thione 2a reacted with ethylenebis(triphenylphosphine)platinum or tetrakis(triphenylphosphine)palladium to afford the corresponding dithiolato-platinum (20) and dithiolato-palladium (21) complexes in good yields.     

Reaction of selenofenchone with propiolic acid: first instance of Wagner-Meerwein rearrangement in selone

The reaction of selenofenchone (3a) with propiolic acid in refluxing chloroform produced selenodioxenone (4) along with rearranged product (5b), while 5b was obtained in almost quantitative yield under solvent-free conditions. In the presence of Lewis acid, selenofenchone 3a reacted with methyl propiolate to afford corresponding rearranged adduct (7).     

Living radical polymerizations with germanium, tin, and phosphorus catalysts--reversible chain transfer catalyzed polymerizations (RTCPs)

A novel class of living radical polymerizations with germanium, tin, and phosphorus catalysts were developed. The polymerizations are based on a new reversible activation mechanism, Reversible chain Transfer (RT) catalysis. Low-polydispersity (M(w)/M(n) approximately 1.1-1.3) polystyrene, poly(methyl methacrylate), poly(glycidyl methacrylate), and poly(2-hydroxyethyl methacrylate) with predicted molecular weight were obtained with fairly high conversion in a fairly short time. The pseudo-first-order activation rate constant kact for the styrene/GeI4 (catalyst) system was large enough, even with a small amount of GeI4, explaining why the system provides low-polydispersity polymers from an early stage of polymerization. The retardation in the polymerization rate observed for the styrene/GeI4 system was kinetically proven to be mainly due to the cross-termination between the propagating radical with GeI3*. Attractive features of the germanium, tin, and phosphorus catalysts include their high reactivity hence small amounts (1-10 mM) being required under relatively mild conditions (at 60-100 degrees C), high solubility in organic media without ligands, insensitivity to air hence sample preparation being allowed in the air, and minor color and smell. The germanium and phosphorus catalysts may also be attractive for their low toxicity. The phosphorus catalysts may also be attractive for their low cost.     

Transient diffusion and cluster formation of water molecules on Rh(111) at 20 K

The authors investigated the initial stage of water adsorption on Rh(111) at 20 K, using infrared reflection absorption spectroscopy. In this low coverage region, isolated water molecules and small water clusters are observed. Since thermal diffusion is suppressed at 20 K, the formation of water clusters at low coverage is controlled by both coverage and transient diffusion on the surface. Within a simple random walk model of the transient diffusion and clustering process, the authors estimate the mean lateral displacement from the first impact point to the final adsorption site to be 7.6 A; an incoming water molecule on Rh(111) is trapped with eight postcollision hops on the average.     

Carbocupration of 1-alkynylphosphines followed by trapping with electrophiles

Treatment of 1-alkynylphosphine with magnesium dialkylcuprate in ether results in regio- and stereoselective syn-carbocupration. The alkenylcopper intermediate reacts with electrophile, which leads to allylation, acylation, and phosphination. The phosphination offers a new route to gem-diphosphinoalkene, an interesting phosphorus-based organic structure.     

Single-molecule measurements with a single quantum dot

Recent progress of quantum dot (QD) applications in single-molecule measurements are reviewed in this paper. Bright fluorescence and anti-photobleaching properties of QDs have explored the way to conduct long-time trajectory tracking of transmembrane proteins both in vitro and in vivo. Coupled with diversities of chemical and biochemical modifications of QD surfaces, their application fields are expanding to multidiscipline fields including imaging on the basis of a single molecule. Currently, molecular interactions and conformational changes on the QD surface can be detected at a single-molecule level. These expansions of application fields also involve toxicity problems in cells since most commercially available QDs consist of cadmium selenide or cadmium telluride, which are inherently toxic. For widespread applications of QDs including in vivo and therapeutic use in place of current organic fluorophore, cytotoxicity is discussed as well in this paper. 10.1002/tcr.20128.