Synthesis of 5-heteroarylazulenes: first selective electrophilic substitution at the 5-position of azulene

1,3-Di-tert-butylazulene reacted with highly electrophilic trifluoromethanesulfonate of N-containing heterocycles to give 5-(dihydroheteroaryl)azulene derivatives in good yield and treatment of the 5-(dihydroheteroaryl)azulene derivatives with KOH afforded 5-(heteroaryl)azulenes in excellent yield.     

Collection of mercury from artificial sea-water with activated carbon

Nanogram amounts of mercury(II) and methylmercury in artificial sea-water containing mineral acids as preserving reagents were shown to be collected quantitatively with activated carbon. Mercury concentrated on activated carbon was determined directly by combustion, trapping on gold and electrothermal atomic-absorption spectrophotometry. The activated carbon was purified by heating at 350 degrees for 2 hr. Sulphuric acid and hydrochloric acid were purified by treatment with activated carbon. Interference from iodide was eliminated by using a carbonate buffer wash before the atomic-absorption measurement. Less than 4 ng of mercury in 200-300 ml of artificial sea-water, whether acidified or not (with sulphuric, hydrochloric or nitric acid), was satisfactorily collected with 100 mg of activated carbon. Mercury was also collected quantitatively after oxidative treatment of artificial sea-water.     

Ruthenium-catalyzed carbonylative cycloaddition of alpha-keto lactones with alkenes or alkynes: the participation of an ester-carbonyl group in cycloaddition reactions as the two-atom assembling unit

The reaction of benzofuran-2,3-dione derivatives 1 with CO and alkenes (or alkynes) results in a carbonylative [2+2+1] cycloaddition in which the ester-carbonyl group is incorporated into a two-atom assembling unit to give spirolactone derivatives 2. This reaction provides the first example of an ester-carbonyl group participating in a carbonylative cycloaddition reaction.     

Photopolymerization of cyclohexene oxide by use of o-nitrobenzyl triphenylsilyl ether/aluminum compound catalyst. Dependence of catalyst activity on the structure of the silyl ether

o-Nitrobenzyl triphenylsilyl ehther/aluminum compound has been previously shown by the authors to act as catalyst in the photopolymerization of epoxides. The dependence of the structure of the silyl ether on the catalyst activity was examined. There were two steps in the photopolymerization. The first step (“Step 1”) is photodecomposition of the silyl ether to silanol. The second step (“Step 2”) is the initiation of polymerization by silanol and the aluminum compound. The introduction of an electron withdrawing group, Cl, CF₃, on the benzene ring bonded to Si made the quantum yield of Step 1 low, however, the rate of Step 2 was increased. The low quantum yield of Step 1 was explained in terms of the rate of electron transfer that is controlled by the relative electron density between the CH₂ and NO₂ in the o-nitrobenzyl group. The acceleration of Step 2 was explained in terms of an increase in silanol acidity that was promoted by the introduction of an electron withdrawing group. The overall rate of the photopolymerizatiol depends to a greater degree on the rate of Step 2 than on that of Step 1.     

Investigation of the detection limit for the determination,by pyrolysis-capillary GC,of the thickness of ultra thin PMMA layers coated on to PET film

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.     

Spectrophotometric determination of zirconium, uranium, thorium and rare earths with arsenazo III after extractions with thenoyltrifluoroacetone and tri-n-octylamine

A method is described for the spectrophotometric determination of microgram amounts of zirconium, uranium(VI), thorium and rare earths with Arsenazo III after systematic separation by extraction. First zirconium is extracted into a xylene solution of thenoyltrifluoroacetone (TTA) from about 4M hydrochloric acid. Uranium(VI) is then extracted into a xylene solution of tri-n-octy lamine from about 4M hydrochloric acid. Thorium is next extracted into TTA solution at pH about 1.5, and finally rare earths are extracted into TTA solution at pH about 4.7. Each metal is back-extracted from the organic phase before determination.     

Iron‐ and Bismuth‐Catalyzed Asymmetric Mukaiyama Aldol Reactions in Aqueous Media

We have developed asymmetric Mukaiyama aldol reactions of silicon enolates with aldehydes catalyzed by chiral Fe^II and Bi^III complexes. Although previous reactions often required relatively harsh conditions, such as strictly anhydrous conditions, very low temperatures (?78 °C), etc., the reactions reported herein proceeded in the presence of water at 0 °C. To find appropriate chiral water‐compatible Lewis acids for the Mukaiyama aldol reaction, many Lewis acids were screened in combination with chiral bipyridine L1 , which had previously been found to be a suitable chiral ligand in aqueous media. Three types of chiral catalysts that consisted of a Fe^II or Bi^III metal salt, a chiral ligand ( L1 ), and an additive have been discovered and a wide variety of substrates (silicon enolates and aldehydes) reacted to afford the desired aldol products in high yields with high diastereo‐ and enantioselectivities through an appropriate selection of one of the three catalytic systems. Mechanistic studies elucidated the coordination environments around the Fe^II and Bi^III centers and the effect of additives on the chiral catalysis. Notably, both Brønsted acids and bases worked as efficient additives in the Fe^II‐catalyzed reactions. The assumed catalytic cycle and transition states indicated important roles of water in these efficient asymmetric Mukaiyama aldol reactions in aqueous media with the broadly applicable and versatile catalytic systems.