Evaluation of Photocatalytic Activity of Transparent Anatase Nanocrystals-Dispersed Silica Films Prepared by the Sol-Gel Process with Hot Water Treatment

Anatase nanocrystals were precipitated mainly at the surface of the silica-titania gel films with hot water treatment, whereas the addition of poly(ethylene glycol) (PEG) in the films led to the dispersion of anatase nanocrystals in the whole of the films after the treatment. Both films with and without PEG showed high photocatalytic activities for acetaldehyde, NO _x and stearic acid in the gas-solid system, and for methylene blue and potassium iodide in the liquid-solid system. The addition of PEG improved the photocatalytic activities of the resultant films due to the smaller anatase crystallites and the porous film structure. The residual silica under-layer of the superficially anatase-precipitated films is expected to act as a protective one for an organic polymer substrate against the photocatalytic degradation.     

Rapid ruthenium-catalyzed synthesis of pyranopyrandiones by reconstructive carbonylation of cyclopropenones involving C[bond]C bond cleavage

Pyranopyrandiones were prepared by a novel ruthenium-catalyzed carbonylative dimerization of cyclopropenones via C-C bond cleavage. For example, treatment of dipropylcyclopropenone with a catalytic amount of Ru3(CO)12 and NEt3 in THF under 15 atm of carbon monoxide at 140 degrees C for 20 h gave a novel functional monomer, 3,4,7,8-tetrapropylpyrano[6,5-e]pyran-2,6-dione, in an isolated yield of 81%. Unsymmetrically substituted pyranopyrandiones were also obtained by ruthenium-catalyzed carbonylative coupling of cyclopropenones with alkynes under similar reaction conditions.     

Gas Chromatographic Separation of Carbonyl Compounds as Their 2,4-dinitrophenylhydrazones Using Glass Capillary Columns

The gas chromatographic separation of 22 carbonyl compounds as their 2,4-dinitrophenylhydrazones was investigated using glass capillary columns. Complete separation of the 2,4-dinitrophenylhydrazones of ten aliphatic aldehydes, eight aliphatic ketones and four aromatic aldehydes was obtained, except for the derivatives of n-valeraldehyde and isobutyl methyl ketone, whose peaks overlapped, and the o- and m-tolualdehyde derivatives, which were poorly separated. The optimum conditions were as follows: stationary phase, SF-96; column size, 20 m × 0.25 mm I.D. ; column temperature, 200-240°; injection and detector temperatures, 280-290°; carrier gas flow-rate, helium 1.0-1.2 ml/min or nitrogen 1.1-1.2 ml/min. The method was applied to the analysis of aliphatic carbonyl compounds in car exhaust fumes and cigarette smoke.     

Selective reduction of tertiary alkyl,benzyl, and allyl halides to hydrocarbons using lithium 9,9-di-n-butyl-9-borabicyclo[3.3.1]nonanate

The title 9-borabicyclo[3.3.1]nonane(9-BBN) ate complex (1) brings about selective removal of tertiary alkyl, benzyl and allyl halides to give the corresponding hydrocarbons in excellent yields without concomitant attack on secondary, primary and aryl derivatives. The reduction of cis- and trans - 4 - t - butyl - 1 - methylcyclohexyl chlorides (2) with 1 gives 4 - t - butyl - 1 - methylcyclohexanes (3) with partial inversion of configuration in cyclohexane, while that in benzene gives thermodynamically stable trans-3 predominantly. The reactions of 1,1 - dimethyl - 5 - hexenyl chloride (4) and 1,7,7 - trimethylbicyclo[2.2.1]hept - 2 - yl chloride (8) with 1 proceed with the rearrangements characteristic to a carbonium ion intermediate. The reduction of 1 - ethyl - 1 - methylpentyl chloride with 1 follows a second-order rate equation.     

Cyclopalladation of the indole ring in palladium(II) complexes of 2N1O-donor ligands and its dependence on the O-donor properties

Synthetic, structural, spectroscopic, and kinetic studies have been carried out on the Pd(II) complexes of new 2N1O-donor ligands containing a pendent indole, 3-(N-2-pyridylmethyl-N-2-hydroxy-5-methoxybenzylamino)ethylindole (HMeO-iepp), 3-(N-2-pyridylmethyl-N-2-hydroxy-5-nitrobenzylamino)ethylindole (HNO2-iepp), and (N-2-pyridylmethyl-3-indolylethylamino)acetic acid (Hiepc) (H denotes a dissociable proton). [Pd(MeO-iepp)Cl] (2), [Pd(NO2-iepp)Cl] (3), and [Pd(iepc)Cl] (4) were prepared and revealed by X-ray analysis to have a pyridine nitrogen, an amine nitrogen, a phenolate or carboxylate oxygen, and a chloride ion in the coordination plane. UV absorption and 1H NMR spectral changes indicated that all the complexes could be converted to the indole-binding complexes where the O donor was replaced by the indole C2 atom by cyclopalladation in DMSO or DMF in the temperature range of 40-60 degrees C. Formation of the indole-binding complex species obeyed the first-order kinetics, from which the activation parameters were estimated. The formation rate was dependent on the properties of the O-donor group, a lower pKa value of its conjugate acid causing faster conversion to the indole-binding species in the order 2 (methoxyphenolate) < 3 (nitrophenolate) < 4 (carboxylate). On the other hand, the ratio of the indole-binding complex to the O-donor complex as a result of the conversion was greater for the complexes with a higher pKa value of the ligand OH group, the order being 2 > 3 > 4.     

Polymerization of methacrylates. I. Polymerization reactivity of picryl methacrylate

The polymerization of picryl (PMA), 2,4-dinitrophenyl (2,4-DNMA),2,6-dinitrophenyl (2,6-DNMA), 2-methyl-4,6-dinitrophenyl (MDNMA), and 2,6-dimethylphenyl methacrylates (DMMA) was carried out in benzene at 60°C. PMA, 2,6-DNMA, and MDNMA did not undergo radical homopolymerization, while 2,4-DNMA and DMMA did. The results suggest that the growing radical readily attacks the oxygen atom of the nitro group at the 2 position of the terminal phenyl group due to the steric effect of the substituent at the 6 position, resulting in chain termination. PMA formed a charge-transfer complex with 2-naphthyl methacrylate (NMA). The stoichiometric composition of this complex was shown to be 1:1 molar complex. PMA was readily copolymerized with NMA. The amount of solvent affected the composition of the copolymer obtained at a given same mole fraction in feed. The results suggest that charge-transfer interaction between the ester groups affects the copolymerization mechanism.     

PtBr2-catalyzed consecutive enyne metathesis-aromatization of 1-(1-methoxy-but-3-enyl)-2-(1-alkynyl)benzenes: dual role of the Pt catalyst

1,7-Enynes 1, connected through an aromatic ring and bearing a leaving methoxy group at the 4-position, underwent the PtBr(2)-catalyzed enyne metathesis followed by aromatization in one pot to afford vinyl naphthalenes 3 in good to acceptable yields. The cyclobutene intermediate 11a and another intermediate 2a were isolated, indicating that PtBr(2) acts as a dual role catalyst: (1) as a transition metal catalyst, it induces the enyne metathesis to produce 11a starting from 1a, and (2) as a Lewis acid catalyst, it facilitates elimination of MeOH from 2a to give the aromatized product 3a.     

Chemo-enzymatic Synthesis of Novel Oligo-N-acetyllactosamine Derivatives having a β(1-4)–β(1-6) Repeating Unit by Using Transition State Analogue Substrate

Chitinase-catalyzed hydrolytic and transglycosylating behavior of 1,2-oxazoline derivative of N-acetyllactosamine (LacNAc-oxa) 1 has been investigated. An extremely rapid hydrolysis (ring-opening of the oxazoline moiety) could be observed, suggesting that 1 behaves as a transition state analogue substrate for chitinase A1 (Bacillus circulans WL-12). This disaccharide monomer 1 was found to polymerize under basic conditions, giving rise to novel oligosaccharides having a β(1-4)–β(1-6) repeating unit in the main chain. The degree of polymerization of the resulting oligosaccharides was up to 5. This is the first example of enzymatic glycosylation reaction forming a β(1-6) bond catalyzed by chitinase.     

Cu(I) catalyst in DMF: an efficient catalytic system for the synthesis of furans from 2-(1-alkynyl)-2-alken-1-ones

The cyclization of 2-(1-alkynyl)-2-alken-1-ones 1 proceeded very smoothly in the presence of alcohols 2 with a catalytic amount of Cu(I)Br in DMF at 80 degrees C, leading to the formation of highly substituted furans 3. The catalytic system reported herein is easy to handle, compared to the previously known system wherein the reaction between 1 and 2 needed to use moisture sensitive gold(III) chloride.