An efficient multicomponent and stereoselective synthesis of new spiro[indeno[1,2‐b]quinoxaline‐11,2′‐pyrrolidine] derivatives

New spiro[indeno[1,2‐b]quinoxaline‐11,2′‐pyrrolidine] derivatives were prepared in high yield stereoselectively from an efficient multicomponent 1,3‐dipolar cycloaddition reaction between ninhydrin, phenylenediamine, sarcosine, and chalcones. The regiochemistry and stereochemistry of resultant cycloadducts have been determined by several 2D NMR spectroscopic techniques and X‐ray single crystal diffraction. J. Heterocyclic Chem., (2012).     

A redox series of aluminum complexes: characterization of four oxidation states including a ligand biradical state stabilized via exchange coupling

Electrophilic activation and subsequent reduction of substrates is in general not possible because highly Lewis acidic metals lack access to multiple redox states. Herein, we demonstrate that transition metal-like redox processes and electronic structure and magnetic properties can be imparted to aluminum(III). Bis(iminopyridine) complexes containing neutral, monoanionic, and dianionic iminopyridine ligands (IP) have been characterized structurally and electronically; yellow (IP)AlCl(3) (1), deep green (IP(-))(2)AlCl (2) and (IP(-))(2)Al(CF(3)SO(3)) (3), and deep purple [(IP(2-))Al](-) (5) are presented. The mixed-valent, monoradical complex (IP(-))(IP(2-))Al is unstable toward C-C coupling, and [(IP(2-))Al](2-)(μ-IP-IP)(2-) (4) has been isolated. Variable-temperature magnetic susceptibility and EPR spectroscopy measurements indicate that the biradical character of the ligand-based triplet in 2 is stabilized by strong antiferromagnetic exchange coupling mediated by aluminum(III): J = -230 cm(-1) for ? = -2J(?(L(1))·?(L(2))). Coordination geometry-dependent (IP(-))-(IP(-)) communication through aluminum(III) is observed electrochemically. The cyclic voltammogram of trigonal bipyramidal 2 displays successive ligand-based oxidation events for the two IP(1-/0) processes, at -0.86 and -1.20 V vs SCE. The 0.34 V spacing between redox couples corresponds to a conproportionation constant of K(c) = 10(5.8) for the process (IP(-))(2)AlCl + (IP)(2)AlCl → 2(IP(-))(IP)AlCl consistent with Robin and Day Class II mixed-valent behavior. Tetrahedral 5 displays localized, Class I behavior as indicated by closely spaced redox couples. Furthermore, CV's of 2 and 5 indicate that changes in the coordination environment of the aluminum center shift the potentials for the IP(1-/0) and IP(2-/1-) redox couples by up to 0.9 V.     

Photocatalytic reforming of biomass-derived feedstock to hydrogen production

Research on Chemical Intermediates - Worldwide energy and environmental issues are forcing researchers to develop a green approach to produce a clean energy. However, traditional methods in...     

三溴化聚乙烯吡咯烷酮高效催化醇和酚的乙酰化反应(英文)

An efficient and versatile procedure for the acetylation of alcohols and phenols using acetic anhydride in the presence of a catalytic amount of polyvinylpolypyrrolidoniume tribromide has been successfully developed.Primary,secondary,and tertiary alcohols,as well as a selection of the phenolic compounds,have been successfully acetylated according to this procedure,with good to high yields being achieved over short reaction times.     

A Facile and Efficient Synthesis of Arylsulfonamido‐Substituted 1,5‐Benzodiazepines and N‐[2‐(3‐Benzoylthioureido)aryl]‐3‐oxobutanamide Derivatives

A facile and efficient synthesis of 1,5‐benzodiazepines with an arylsulfonamido substituent at C(3) is described. 1,5‐Benzodiazepine, derived from the condensation of benzene‐1,2‐diamine and diketene, reacts with an arylsulfonyl isocyanate via an enamine intermediate to produce the title compounds of potential synthetic and pharmacological interest in good yields (Scheme 1). In addition, reaction of benzene‐1,2‐diamine and diketene in the presence of benzoyl isothiocyanate leads to N‐[2‐(3‐benzoylthioureido)aryl]‐3‐oxobutanamide derivatives (Scheme 2). This reaction proceeds via an imine intermediate and ring opening of diazepine. The structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme 3).     

Correction to: Linear formulations and valid inequalities for a classic location problem with congestion: a robust optimization application

Optimization Letters - In the original publication of the article, the name of the corresponding author was incorrectly published as “Amir Ahamdi”.     

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.     

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.     

Investigation of kinetic and mechanism of triphenylphosphine addition to para‐naphthoquinone

This work reports the results of a kinetic and mechanistic investigations of the addition reaction of triphenylphosphine to para‐naphtoquinone in 1,2‐dichloromethane as solvent. The order of reaction with respect to the reactants was determined using initial rate method, and the rate constant was obtained on the basis of pseudo‐first‐order method. Variable time method using Uv–Vis spectrophotometry (at 400 nm) was utilized for monitoring this addition reaction, for which the following Arrhenius equation was obtained: The resulting activation parameters E_a, ΔH^#, ΔG^#, and ΔS^# at 300 K were 13.63, 14.42, 18.75 kcal mol^?1, and ?14.54 cal mol^?1K^?1, respectively. The results suggest that the reaction is first order with respect to both triphenylphosphine and para‐naphthoquinone. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 427–433, 2005