A facile synthesis of chromeno[3,4-c]spiropyrrolidine-oxindoles via 1,3-dipolar cycloadditions

A facile one-pot synthesis of chromene bearing novel spiropyrrolidine-oxindoles has been accomplished by the [3+‏2]-cycloaddition reaction of 3-acetyl-2H-chromen-2-ones with azomethine ylides derived in situ from isatin or N-methyl isatin with sarcosine.     

One-pot synthesis of 1,2-disubstituted pyrrolo[2,3-b]quinoxalines via palladium-catalyzed heteroannulation in water

The reaction of N-alkyl-3-chloroquinoxaline-2-amines with 1-alkynes, catalyzed by Pd-Cu, in the presence of sodium lauryl sulfate as the surfactant in water, leads to the one-pot formation of 1,2-disubstituted pyrrolo[2,3-b]quinoxalines in good-to-high yields.     

Zero divisors and units with small supports in group algebras of torsion-free groups

Kaplansky’s zero divisor conjecture (unit conjecture, respectively) states that for a torsion-free group G and a field 𝔽, the group ring 𝔽[G] has no zero divisors (has no units with supports of size greater than 1). In this paper, we study possible zero divisors and units in 𝔽[G] whose supports have size 3. For any field 𝔽 and all torsion-free groups G, we prove that if αβ = 0 for some non-zero α,β∈𝔽[G] such that |supp(α)| = 3, then |supp(β)|≥10. If 𝔽 = 𝔽₂ is the field with 2 elements, the latter result can be improved so that |supp(β)|≥20. This improves a result in Schweitzer [J. Group Theory, 16 (2013), no. 5, 667–693]. Concerning the unit conjecture, we prove that if αβ = 1 for some α,β∈𝔽[G] such that |supp(α)| = 3, then |supp(β)|≥9. The latter improves a part of a result in Dykema et al. [Exp. Math., 24 (2015), 326–338] to arbitrary fields.     

One-pot and stereoselective synthesis of 2,3-dihydro-1,5-benzodiazepin-2-one with a phosphanylidene or phosphono-succinate substituent

The one-pot synthesis of 2,3-dihydro-1,5-benzodiazepins-2-one bearing phosphanylidene (ylide) or phosphono-succinate substituent is described. In this four-component reaction, benzodiazepine derived from condensation of o-phenylenediamine and diketene is trapped with the trialkyl phosphite-dialkyl acetylenedicarboxylate zwitterion. In the presence of H₂O, the ylide functional group is hydrolyzed to the corresponding phosphonate. The configuration of the products is selective and only one of the two possible rotamers or diastereomers is formed exclusively in high yield.     

Multiple criteria facility location problems: A survey

This paper provides a review on recent efforts and development in multi-criteria location problems in three categories including bi-objective, multi-objective and multi-attribute problems and their solution methods. Also, it provides an overview on various criteria used. While there are a few chapters or sections in different location books related to this topic, we have not seen any comprehensive review papers or book chapter that can cover it. We believe this paper can be used as a complementary and updated version.     

A Straightforward Method for the Synthesis of Functionalized Trisubstituted Alkenes through Na2S/Al2O3 Catalyzed Knoevenagel Condensation

Na₂S/Al₂O₃ catalyzed the Knoevenagel condensation between an aldehyde and an active methylene compound to yield various trisubstituted alkenes.     

Quasiconvexity and uniqueness of stationary points in the multi-dimensional calculus of variations

Let be a bounded starshaped domain. In this note we consider critical points of the functional

where of class satisfies the natural growth

for some and 0$">, is suitably rank-one convex and in addition is strictly quasiconvex at . We establish uniqueness results under the extra assumption that is stationary at with respect to variations of the domain. These statements should be compared to the uniqueness result of Knops & Stuart (1984) in the smooth case and recent counterexamples to regularity produced by Müller & Sverák (2003).

     

Oxidation of Primary Alcohols to Carboxylic Acids Using Silica Supported CrO3/H5IO6 Under Microwave Irradiation in a Solvent‐Free System

Chromium trioxide/periodic acid supported onto wet silica gel oxidizes primary alcohols to the corresponding carboxylic acids in very short reaction times in very good yields.     

Thermodynamics of the solvent extraction of thorium and europium nitrates by neutral phosphorylated ligands

Solvent extraction of tetravalent thorium and trivalent europium ions from nitrate media into dichloromethane solution of triphenylphosphine oxide (TPPO) has been studied. The extractant was shown to be more efficient for europium than for thorium. A conventional log-log analysis reveals that the extraction of both metal nitrates takes place via the formation of the species with 1 : 2 metal to ligand ratio. Thermodynamic parameters i.e., ΔG°, ΔH° and ΔS° of the extraction process using 1,2-dichloroethane as diluent have been calculated based on the influence of the temperature on extraction equilibria in the range 293-313 K. While the extraction of europium is controlled by enthalpy changes, the extraction of thorium is an endothermic process and is driven by entropy changes. A comparison of these data with those obtained for the extraction of europium and thorium nitrates by two other related phosphorylated ligands, tri-n-octylphosphine oxide (TOPO) and diphenyl-N,N-dimethylcarbamoylmethylphosphine oxide (DФDMCMPO), indicates that DФDMCMPO coordinates presumably as a chelating ligand. This revised version was published online in July 2006 with corrections to the Cover Date.