Preparation of Protected α-Alkoxyglycines

N-Carbobenzoxy-α-alkoxyglycine esters were synthesized by H₂SO₄-catalyzed O-alkylation of N-carbobenzoxy-α-hydroxyglycine and also by base treatment of N-carbobenzoxy-N-chloroglycine methyl ester in the corresponding alcohol. Saponification of the protected α-alkoxyglycines gave free acids which can be used for the synthesis of α-alkoxyglycine residue-containing peptides.     

MMPP (Magnesium Monoperoxyphthalate) in Acetonitrile; A New Approach to the Synthesis of Lactones via Baeyer-Villiger Oxidation of Cyclic Ketones

A variety of unsubstituted and mono- or di-substituted cycloalkanones can be oxidised with modest excess of magnesium monoperoxyphthalate hexahydrate in acetonitrile to produce the corresponding lactones in a facile, selective, and high yielding manner.     

Selectivity in Consecutive SNAr-Dequaternization Reactions of Chlorodiazines with Tertiary Amines

Consecutive S_NAr-dealkylation reactions of chlorodiazines such as 2-chloropyrimidine and 3, 6-dichloropyridazine with tertiary amines took place in a highly selective fashion.     

Electrochemical and Electrochromic Properties of Polymer Complex Films Composed of Polytetramethyleneviologen and Poly-[p-Styrenesulfonic Acid] Containing a Conductive Powder

The electrochemical and electrochromic properties of polymer films containing a conductive powder (SnO₂/TiO₂) have been investigated. The films are complexes of polytetramethyleneviologen and poly(p-styrenesulfonic acid). It was found that the coloration (purple) and bleaching rates of the composite films increase markedly with increasing conductive powder content(x). The coloring and bleaching of the composite film with x = 95 wt% were about 7 and 44 times faster, respectively, than those for an equivalent film without conductive powder. This increase in the rate of color change by introduction of a conductive powder was found to be correlated with the apparent diffusion coefficient (D _app) for the diffusionlike charge-transport process within the composite films which increases with increasing x. The D _app for the reduction process of the film with x = 95 wt% was larger by about 3 orders of magnitude than that for the unfilled film.     

Novel Synthesis of a Macromonomer Having Organosilyl and Amino Groups

Abstract

Reaction between dimethyldivinylsilane (1) and N,N′-diethyl-N-lithio-ethylenediamine (2a) in the presence of N,N′-diethylethylenediamine (3a) in THF at 20°C gave a monoadduct, 3,3-dimethyl-6-ethyl-3-sila-6,9-diaza-1-undecene (4a). An anionic self-polyaddition reaction of 4a in the presence of lithium diisopropylamide (LDA) proceeded to form oligomers. Each of the oligomers thus obtained was found to carry a polymerizable vinylsilane moiety at the oligomer chain terminal. As a result, a new type of macromonomer having alternating repeating units of ethylenediamine and organosilyl groups was synthesized. Acid-base titration showed the macromonomer to have unique characteristics on protonation of diamine moieties. Anionic polyaddition reactions between 1 and N-lithio-piperazine (2b) in the presence of piperazine (3b) also gave a macromonomer consisting of alternating repeating units of piperazine and organosilyl groups (4b). Radical copolymerizations of styrene with 5b gave comblike graft copolymers.     

Oligomerization of Substituted Phenyl Glycidyl Ethers with Tertiary Amine

The oligomerization of substituted phenyl glycidyl ethers was studied kinetically in the presence of dimethylbenzylamine using toluene or dioxane as a solvent. The infrared spectra of the resultant oligomers suggest that the reaction products have the internal carbon-carbon double-bond un-saturation, which is confirmed by the catalytic hydrogenation. The molecular weights of the oligomers also suggest that γ-phenoxy allyl alcohol produced by the initial reaction step, in which the γ-proton of phenyl glycidyl ether is attracted by a base, amine, reacts with other phenyl glycidyl ether and thus proceeds further, yielding the oligomer. The value of the reaction constant ρ is obtained positive for this reaction, which indicates that electron-withdrawing substituents of phenyl gylcidyl ethers increase the rate of oligomerization. A kinetic analysis shows that the proposed reaction sequence accounts for all the characteristics of the polymerization including sigmoidal shapes of monomer consumption curves, reaction rates, and induction periods.     

Copper‐Catalyzed Electrophilic Etherification of Arylboronic Esters with Isoxazolidines

A copper‐catalyzed electrophilic etherification of arylboronic esters is reported. Isoxazolidines are utilized as easily available and stable [RO]⁺ surrogates to give 1,3‐amino aryl ethers. The O‐selective arylation of isoxazolidines takes place without causing competitive N‐arylation. In contrast to previously reported anionic conditions, our copper‐catalyzed conditions are mild enough to achieve high functional group tolerance. Preliminary mechanistic studies and DFT calculations support that the reaction proceeds via a transmetalation/oxidative addition pathway, followed by a Lewis acid‐promoted reductive elimination to induce the crucial O‐selectivity.     

Temporal variation of atmospheric polycyclic aromatic hydrocarbon concentrations in PM10 from the Kathmandu Valley and their gas-particle concentrations in winter

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM) with a diameter <10 µm (PM₁₀, 50% cut off) were investigated in the Kathmandu Valley, Nepal, during 2003. In order to understand the dynamics of atmospheric PAHs in winter, the PAH concentrations in total PM and in the gaseous phase were investigated in the valley in December 2005. Total of 45 PAH compounds (∑45PAHs) were analysed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). In 2003, the ∑45PAH concentrations in PM₁₀ ranged between 4.3 and 89 ng m^?3 (annual average; 27 ± 24 ng m^?3). The average concentrations of ∑45PAHs in December 2005 were 210 ± 33 ng m^?3 in total PM and 430 ± 90 ng m^?3 in the gaseous phase. The ∑45PAH concentration in PM accounted for more than 30% of the sum of their particulate and gaseous forms. Phenanthrene (Ph) was the most predominant compound in the gaseous phase, whereas four- to seven-ring PAHs were predominant in total PM. The highest values of ∑45PAHs occurred in the winter and spring. Estimates of emission sources based on diagnostic molecular ratios showed that atmospheric PAHs in the Kathmandu Valley mainly originated from the exhaust gas of diesel engine. In the winter and spring, PAH pollution would be accelerated by the operations of brick kilns and the frequent formation of an atmospherically stable layer in the valley.     

Mononuclear Manganese–Peroxo and Bis(μ‐oxo)dimanganese Complexes Bearing a Common N‐Methylated Macrocyclic Ligand

Mononuclear Mn^III–peroxo and dinuclear bis(μ‐oxo)Mn^III₂ complexes that bear a common macrocyclic ligand were synthesized by controlling the concentration of the starting Mn^II complex in the reaction of H₂O₂ (i.e., a Mn^III–peroxo complex at a low concentration (≤1 mM ) and a bis(μ‐oxo)Mn^III₂ complex at a high concentration (≥30 mM )). These intermediates were successfully characterized by various physicochemical methods such as UV–visible spectroscopy, ESI‐MS, resonance Raman, and X‐ray analysis. The structural and spectroscopic characterization combined with density functional theory (DFT) calculations demonstrated unambiguously that the peroxo ligand is bound in a side‐on fashion in the Mn^III–peroxo complex and the Mn₂O₂ diamond core is in the bis(μ‐oxo)Mn^III₂ complex. The reactivity of these intermediates was investigated in electrophilic and nucleophilic reactions, in which only the Mn^III–peroxo complex showed a nucleophilic reactivity in the deformylation of aldehydes.