Palladium-catalyzed oxidation of alcohols via their allyl carbonates under neutral conditions

Treatment of alkyl allyl carbonates derived from various alcohols with a palladium catalyst in MeCN affords ketones and aldehydes in high yields. This new method of oxidation of alcohols can be applied to various alcohols except simple primary alcohols.     

Use of allyl, 2-tetrahydrofuryl, and 2-tetrahydropyranyl ethers as useful C3-, C4-, and C5-carbon sources: palladium-catalyzed allylation of aldehydes

Palladium-diethylzinc or palladium-triethylborane catalytically promotes self-allylation of 2-(allyloxy)tetrahydrofurans, 2-(allyloxy)tetrahydropyrans, and their hydroxy derivatives on the rings (ribose, glucose, mannose, deoxyribose, deoxyglucose). All the reactions proceed at room temperature and provide polyhydroxyl products, sharing a structural motif of a homoallyl alcohol, in good to excellent yields with high levels of stereoselectivity. Useful C3-unit elongation, which makes the best use of an allyl ether as a protecting group and a nucleophilic allylation agent, is demonstrated. Mechanisms for the umpolung reaction (of an allyl ether into an allylic anion) and stereoselectivity associated with allylation of aldehydes are discussed.     

Effects of Aerosol-OT reversed micelles in carbon tetrachloride on acid-base indicator equilibria

ApparentpK _a values of thymol blue solubilized in Aerosol-OT reversed micelles in carbon tetrachloride at 25 °C were determined spectrophotometrically. The effects of the Aerosol-OT concentration and the (water)/(surfactant)R ratio were investigated. The apparentpK _a values increase as a function of increasing (R). All the measuredpK _a values are less than that in water. The decrease ranges from 1.23 units (detergent=0.4 M,R=1.39) to 0.42 units (Aerosol-OT=0.6 M,R=9,25). These results are rationalized in terms of decreased hydronium ion activity in the micellar core due to its binding to the detergent SO₃ ^? groups.     

Novel quinazoline ring synthesis by cycloaddition of N-arylketenimines with N,N-disubstituted cyanamides

The reaction of N-aryl-substituted ketenimines with N,N-disubstituted cyanamides or (MeS)2C=N-CN under high pressure afforded 4-(N,N-disubstituted amino) or 4-(MeS)2C=N-substituted quinazoline derivatives, respectively. These products were formed by [4+2] cycloaddition between the aza-diene moieties of the N-arylsubstituted ketenimines and cyano groups. A 4-(unsubstituted amino)quinazoline derivative was synthesized by hydrolysis of the latter product.     

Synthesis and analgesic activity of novel heterocycles, [1]benzothiopyrano[3,4-b]pyrrole derivatives

In order to develop analgesic compounds possessing a sulfur atom in the alicyclic ring, novel cis-fused heterocycles, [1]benzothiopyrano[3,4-b]pyrrole derivatives (II) were synthesized via a unique cyclization reaction starting from 4-(4-methoxyphenylthio)-2-butanone (1) or 6-methoxy-3,4-dihydro-2H-1-benzothiopyran-4-one (7). The analgesic effects of benzothiopyranopyrroles (16, 18) were measured by means of the writhing test. The phenolic derivative 18 completely inhibited the appearance of writhing at the dose of 50 mg/kg, but the methoxy derivative 16 had no analgesic effect.     

New 1,1-amino hydroperoxides from regioselective oxygenation of 4-(n-arylmethyleneamino)-2,6-di-t-butylphenols.

The oxygenation of 4-(N-arylmethyleneamino)-2,6-di-$\text{t}$-butylphenols with Co(Salpr), a five coordinate Co(II0 Schiff base complex, in CH₂Cl₂ results in the regioselective hydroperoxylation at the imino carbon to give N-(l-aryl-l-hydroperoxymethyl)-3,5-di-$\text{t}$-butyl-$\text{p}$-benzoquinone monoimines, which give exclusively the corresponding amides and 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone in an aerobic solution of KOH in 90% EtOH.     

Photochemical preparation of poly(N-vinyl-2-pyrrolidone)-stabilized platinum colloids and their deposition on titanium dioxide

Preparation processes for Pt-deposited TiO(2) (Pt/TiO(2)) by the synthesis of Pt nanoparticles and their deposition were pursued by transmission electron microscopy, extended X-ray absorption fine structure, UV-vis spectroscopy, and Fourier transform infrared spectroscopic studies. Colloidal dispersions of Pt particles stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) were photochemically synthesized in aqueous ethanol solution. The average diameter of Pt particles was estimated to be 2.0 +/- 0.5 nm, which was almost unchanged by changing the reducing agent from ethanol to methanol and 2-propanol. The PVP-stabilized Pt particles were distributed over a TiO(2) surface only by mixing the Pt colloidal dispersions and TiO(2). CO was chemically coordinated on the Pt particles on a TiO(2) surface after heat treatment was carried out in an O(2) flow at 673 K to completely remove the residual PVP on Pt/TiO(2). Hydrogen reduction at 473 K did not increase the amount of CO adsorbed on Pt sites. The Pt/TiO(2) catalyst after the oxidation treatment showed higher activity for CO photooxidation than that obtained for pure TiO(2) catalyst. The CO photooxidation rate was not unchanged by the H(2) reduction.     

Single molecular multianalyte sensor: jewel pendant ligand

[structure: see text] The jewel pendant ligand has multiple chromogenic units combined in a single molecule with the dyes linked to a semiselective binding site by three heteroatoms (O, N, S) having different HSAB characteristics, to indicate diverse response to individual transition metal ions. Using a single-molecular multianalyte sensor, multiple analytes could be determined with a minimal sensing system.     

Synthetic study of optically active 3-azabicyclo[3.3.0]octane-2,6,8-tricarboxylic acid

Synthesis of (1R,2S,5S,6R,8S)-3-azabicyclo[3.3.0]octane-2,6,8-tricarboxylic acid (2) from trans-4-hydroxy-L-proline (5) was attempted. A Diels-Alder reaction of 3,4-dehydroproline derivative 9 and cyclopentadiene afforded a single stereoisomer 11. The Diels-Alder adduct was smoothly converted to the hydrochloride of 2 (24) via RuO(4) oxidation. Although some racemization of the material or product was observed during the synthetic processes, the amino acid 24 proved to be optically pure.