Recent progress of high-power negative ion beam development for fusion plasma heating

A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D⁻ ion beam. In the preliminary experiment using one ion source, a D⁻ ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D⁻ beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/I_D⁻ < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H⁻ ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator.     

Synthesis and reactivities of 10-S-3 trithiadiazapentalene derivatives

1,3-Bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidinethiones 3a-f reacted with bromine to give trithiadiazapentalene derivatives 5a-f , bearing the exocyclic C-N double bonds, in moderate yields. The molecular structure of 5b was elucidated by the X-ray crystallographic analysis. The treatment of 5b-f with hydrochloric acid gave the ring-opening products, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazo-lidinones 9b-f , accompanied by the production of elemental sulfur. Reduction of 5b , 5d , and 5e with sodium borohydride gave the ring-opening compounds, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidines 13b , 13d , and 13e respectively.     

Palladium-catalyzed cycloheptatriene formation by [3+2+2] cocyclization of 2-substituted allylic alcohols and alkynes

Cycloheptatrienes were obtained by the reaction of 2-substituted allylic alcohols with alkynes in the presence of catalytic amounts of palladium complexes and p-toluenesulfonic acid.     

Diastereoselective preparation and characterization of ruthenium bis(bipyridine) sulfoxide complexes

A new concept in the synthesis of optically active octahedral ruthenium complexes was realized for the first time when cis- or trans-Ru(bpy)2Cl, (cis- or trans-1) was reacted with either (R)-(+)- or (S)-(-)-methyl p-tolyl sulfoxide (2 or 3); this novel asymmetric synthesis leads to the diastereoselective formation of the ruthenium bis(bipyridine) complex cis-delta-[Ru(bpy)2(2)Cl]Cl (4) (49.6% de) or cis-lambda-[Ru(bpy)2(3)Cl]Cl (5) (48.4% de), respectively. cis- or trans-Ru(dmbpy)2Cl2 (cis- or trans-6) (dmbpy = 4,4'-dimethyl-2,2'-bipyridine) also reacts with 2 or 3, leading to the diastereoselective formation of cis-delta-[Ru(dmbpy)2(2)Cl]Cl (7) (59.5% de) or cis-lambda-[Ru(dmbpy)2(3)Cl]Cl (8) (57.2% de), respectively. The diastereoselectivity of these reactions is governed solely by the chirality of the sulfoxide nucleophile. This represents the first process by which a sigma-bonded ligand occupying only a single coordination site has had such an important influence on the stereochemical outcome of a ruthenium bis(bipyridine) complex formation. These novel complexes were fully characterized by elemental analysis and IR, UV/vis, and 1H, 13C, and 2D NMR spectroscopy. An investigation into the chiroptical properties of these novel ruthenium bis(bipyridine) sulfoxide complexes has been carried out, and circular dichroism spectra are used to assign absolute stereochemistry.     

Total synthesis of merrilactone A

Merrilactone A (1) has been shown to possess neurotrophic activity and thus is expected to hold therapeutic potential in the treatment of neurodegeneration diseases. In this paper, we report the total synthesis of (+/-)-1, employing, as key steps, a novel desymmetrization protocol of meso-diketone to construct the core cis-bicyclo[3.3.0]octyl system of 1 (3 --> 2) and a radical cyclization to install the highly congested C9-quaternary carbon (16 --> 17).