Rhodium-catalyzed arylative cyclization of alkynones induced by addition of arylboronic acids

Alkynones react with arylboronic acids in the presence of a rhodium(I) catalyst to afford four- and five-membered-ring cyclic alcohols equipped with a tetrasubstituted exocyclic olefin. The cyclic allylic alcohol skeleton is constructed by the carbon-carbon bond formation between the carbonyl group and an alkenylrhodium(I) intermediate formed by the regioselective addition of an arylrhodium(I) species across the carbon-carbon triple bond.     

Rapid oligosaccharide synthesis using a fluorous protective group

The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS.     

Polymer-Supported dicyanoketene acetal as a pi-acid catalyst: monothioacetalization and carbon-carbon bond formation of acetals

Polymeric dicyanoketene acetals (DCKA) were synthesized by copolymerization of styrene and divinylbenzene or ethylene glycol dimethacrylate. These novel polymers could be used successfully as recyclable pi-acid catalysts in monothioacetalization or carbon-carbon bond forming reaction of acetals.     

Photometric determination of micro amounts of thiosulphate by means of its cyanolysis with lanthanum(III) as catalyst

Lanthanum(III) has been found to catalyse the reaction of thiosulphate with cyanide. The effects of pH, reaction time and temperature, amount of cyanide and lanthanum, and order of addition of reagents have been investigated. Temperature has little effect in the range 10–30°, but at both 35° and 40° the rate is noticeably faster. Reaction is complete at room temperature in 1.5 hr at pH 9.3–9.6, and in 3 hr at pH 9.1–9.6. The method can be applied to the determination of 1.0 × 10⁻⁵−6.0 × 10⁻⁴M thiosulphate, with a relative standard deviation of 0.3% for 4 × 10⁻⁴M thiosulphate.     

Evaluation of the radioactivity in concrete from accelerator facilities

For evaluation of radioactivity induced in the concrete samples from accelerator facilities, the residual radioactivity in concrete sample, collected from seven accelerator facilities, was determined by γ-ray spectrometry. The tritium was extracted by the heating method using an IR furnace, and measured with a liquid scintillation counter. It was found that the major radioisotopes activated mainly by neutrons in the concrete samples were ¹⁵²Eu, ⁶⁰Co, ¹³⁴Cs and ³H. The concentrations of radioactivities induced by thermal neutron capture are the highest at a depth of 10 cm in the concrete wall. The correlation between tritium, ⁶⁰Co and ¹⁵²Eu activity was investigated by measuring many concrete samples for seven accelerator facilities. The results indicate that their activities are strongly correlated with each other. So it would also be concluded that the total activity in shielding concrete could be estimated on the basis of the activities of ⁶⁰Co and ¹⁵²Eu.     

Novel ring transformation reactions of xanthine derivatives

The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed.