Microwave-assisted efficient, one-pot, three-component synthesis of 3,5-disubstituted 1,2,4-oxadiazoles under solvent-free conditions

A novel synthesis of 1,2,4-oxadiazoles is described from a one-pot, three-component reaction between nitriles, hydroxylamine, and aldehydes under microwave irradiation and solvent-free conditions in excellent yields.     

The preparation of quinolines and related fused-ring heterocycles from the dianions of benzoylacetone,certain cyclic ketone oximes,or certain substituted hydrazones

C(α),O-Dilithiooximes, C(α),N-dilithiobenzoylhydrazones, or C(α),N-dilithiocarboalkoxyhydrazones were prepared in an excess of lithium diisopropylamide (LDA) and condensed with 2-aminobenzophenones, or isatoic anhydrides to give intermediates that were treated with aqueous acid, which caused their hydrolysis, cyclodehydration and/or linear dehydration to give products which were substituted quinolines or related fused-ring heterocycles (e.g., cycloheptaquinolines). Dilithiobenzoylacetone was condensed with 2-aminobenzophenones, which was followed by acid cyclodehydration to substituted 2-phenacylquinolines.     

INTERACTION BETWEEN ADSORPTION LAYERS OF MACROMOLECULES

Stability and rheological properties of concentrated emulsions (including those for manufacture of vitamin microcapsules) can be related to elementary coalescence acts and adhesion of emulsion drops interacting through thin layers (microscopic emulsion films) of a dispersion medium

A new procedure was used for measuring the adhesion force f_a between two drops of n-heptane in polymer solutions and lifetime τ of the drops in the contacts depending on the volume concentration C of the polymer, time of formation t_f of adsorption layers, temperature T, capillary pressure P_c in the film, surface area S of the film, and on addition of acetone and tannin. The molecular mechanism of the interaction between adsorption layers of polymers and of the process of film destruction is discussed on the basis of the relationships obtained for interaction free energy Δ F_a, activation energy E, destruction activation volume δ and physico-chemical parameters.     

A peptide bromoiodinane approach for asymmetric bromolactonization

A series of 37 peptides containing an iodo-aryl amide active site were generated by means of both solid phase and conventional synthesis. These peptides were screened for asymmetric induction in the bromolactonization of 4-phenyl-4-pentenoic acid based on the generation of chiral bromoiodinane bromenium sources. The study culminated in the discovery of a tri-peptide iodo-aryl amide that effected the desired bromolactonization in quantitative conversion with 24% ee. The experiments disclosed herein provided valuable insight that ultimately facilitated the development of more synthetically useful enantioselective halocyclization methodology.     

A photocatalytic green system for chemoselective reduction of nitroarenes

A highly efficient photocatalytic reduction of nitroarenes using TiO₂/polyethylene glycol 400-water (TiO₂/PEG–H₂O) is reported. This system at deoxygenated and illuminated (sunlight or violet LED) conditions efficiently reduced nitroarenes using oxalic acid or ammonium formate as a sacrificial electron donor. Reducible functional groups such as chloro, hydroxy, flouro, bromo and carbonyl were intact under the optimized reaction conditions. The 0.1 and 0.5–1 mmol amount of nitroarenes was used under sunlight and violet LED (400 nm) irradiation, respectively. Reusability of the nanotitania was successfully carried out four times. The analyses of the recovered catalyst after five runs including TEM, XRD, TGA and CHN were done and results showed that PEG is located on TiO₂; no change in morphology, crystallinity and particle sizes was observed.     

Investigation of Aqueous Diethanolamine Performance in Prediction of Hydrogen Sulfide and Carbonyl Sulfide Removal from Liquefied Propane

Journal of Solution Chemistry - Hydrogen sulfide and carbonyl sulfide represent undesirable impurities in a variety of industrial gas streams such as natural gas, liquefied natural gas and...     

A note on infinite aS-groups

Let G be a group. If every nontrivial subgroup of G has a proper supplement, then G is called an aS-group. We study some properties of aS-groups. For instance, it is shown that a nilpotent group G is an aS-group if and only if G is a subdirect product of cyclic groups of prime orders. We prove that if G is an aS-group which satisfies the descending chain condition on subgroups, then G is finite. Among other results, we characterize all abelian groups for which every nontrivial quotient group is an aS-group. Finally, it is shown that if G is an aS-group and |G| ≠ pq, p, where p and q are primes, then G has a triple factorization.     

A minimalist NMR approach for the structural revision of mucoxin

In an attempt to revise the structural assignment of mucoxin, and faced with 64 diastereomeric possibilities, we resorted to the synthesis of truncated structures that contained the core stereochemical sites. Twelve stereochemical analogues were synthesized, their (1)H and (13)C NMR spectra were analyzed and four recurring stereochemical trends were distilled from the data. Applying the observed trends to the diastereomeric population pared the possible choices for the correct structure of mucoxin from 64 to 4. Synthesis of these analogues led to the identification of the correct structure of mucoxin.