One-pot synthesis of various xanthene derivatives using ionic liquid 1, 3-disulfonic acid imidazolium hydrogen sulfate as an efficient and reusable catalyst under solvent-free conditions

In this study, 1,3-disulfonic acid imidazolium hydrogen sulfate （DSIMHS） is used as an efficient and reusable ionic liquid for the green, mild, and efficient synthesis of xanthenes under solvent-free conditions. Simple and easy work-up, low cost, green process, short reaction times and excellent yields of the products are the advantages of this procedure. Further, the catalyst can be recycled and reused at least for four times without a noticeably decrease in its catalytic activity.     

Synthesis and antibacterial evaluation of diaminomaleonitrile-based azo-Schiff bases and 8,9-dihydro-7H-purine-6-carboxamides

Research on Chemical Intermediates - Some new DAMN-based Schiff base 6a–6g were synthesized via a condensation reaction of the corresponding azo dyes with...     

Efficient one-pot synthesis of β-hydroxyphosphonates: regioselective nucleophilic ring opening reaction of epoxides with triethyl phosphite catalyzed by Al(OTf)3

A variety of β-hydroxyphosphonates were produced in high yields by ring opening reaction of different types of epoxides with di/trialkyl phosphite esters catalyzed by Al(OTf)₃. The reactions proceeded with complete chemo- and regioselectivity to give the title compounds. This method is new, simple and efficient for the one-pot synthesis of β-hydroxyphosphonates via direct C-P bond formation.     

Complexation thermodynamics of some alkali-metal cations with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane in Acetonitrile

The interaction of 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix5) with alkali-metal cations (Li⁺, Na⁺, K⁺) in aprotic medium (acetonitrile) has been investigated. Conductance measurements demonstrated that 1:1 metal cation:ligand stoichiometries are found with these cations in this solvent. ⁷Li and ²³Na NMR experiments were carried out by titration of the metal cation solutions with Kryptofix5 solution in CD₃CN + CH₃CN at 298 K. Thermodynamic parameters of complexation for this ligand and alkali-metal cations in acetonitrile at 278–308 K were derived from titration conductometry. The highest stability is found for sodium complex. The complexation sequence, based on the value of log K at 278–308 K was found to be Na⁺ > K⁺ > Li⁺.     

Synthesis and solvatochromism study of some new 4-(benzyloxy)-2-((4-aryl)diazenyl)phenols

A series of novel azo disperse dyes were synthesized by coupling reaction of 4-benzyloxyphenol with diazotized p-substituted aniline derivatives as diazo components.These compounds were characterized by spectroscopic techniques and elemental analysis. Ionization constants,pK_a,for these dyes were determined using electronic spectroscopic method.     

An Expedient Synthesis of Novel Derivatives of Pyrido[2,3‐d]pyrimidines Using Magnetically Supported ZrO2 Nanocatalyst

An efficient synthesis of pyrido[2,3‐d]pyrimidine derivatives via one‐pot multicomponent reactions of 6‐amino‐2‐(alkylthio)pyrimidin‐4(3H)‐one, 3‐cyanoacetylindole and arylaldehydes using [Fe₃O₄@ZrO₂] as magnetically recyclable nanocatalyst is reported. This protocol furnished the desired products in good to excellent yields (70–93 %) and lower reaction times. The catalyst could be easily and efficiently separated from the final product solution by an external magnet and be reused in 5 consecutive runs without any significant activity decrease.     

Basic Ionic Liquid as Catalyst and Reaction Media for the One‐pot Three‐component Regioselective Synthesis of Various Thiazol‐2‐imine Derivatives

Thiazol‐2‐imine derivatives were synthesized in an easy and efficient route from the regioselective one‐pot three‐component reaction of aryl amine, alkylisothiocyanate, and various α‐haloketones in [omim][OH] basic ionic liquid. Recyclable reaction media, catalyst free, and short reaction times are the main advantages of this protocol. This method produces the products at room temperature in excellent yields (68–96%). Furthermore, the target compound 6b was determined by X‐ray crystallographic analysis.     

Design,two-directional synthesis,DFT study of new pyrimido[5,4-d]pyrimidine-2,8-dione derivatives

A facile two-directional synthesis of new pyrimido[5,4-d]pyrimidine-2,8-dione was reported via an efficient reaction of premade bis-aldehydes and 1-(2-amino-1,2-dicyanovinyl)-3-phenylurea in the presence of triethylamine as the base and Cu (II) as catalyst. As there is controversy about the formation of two types of products, that is, purine or pyrimidine ring containing compounds in the reaction of diaminomaleonitrile with isocyanates and aldehydes, the computational model chemistry has been employed to obtain new insight about this reaction and determining the dominant pathway of the process. Using DFT model, two alternative pathways have been explored and geometrical isomerization of central double bond has been considered. Accordingly, the evaluated energy barriers affirm the formation of six-membered pyrimidine ring as the major product in the presence of CuCl₂ as the catalyst and MeOH as solvent.     

Ultrasound-promoted regio and chemoselective synthesis of pyridazinones and phthalazinones catalyzed by ionic liquid [bmim]Br/AlCl3

The first ultrasound-promoted multicomponent synthesis of pyridazinones and phthalazinones from arenes, cyclic anhydrides and ArNHNH₂ in the presence of an efficient recyclable catalyst, [bmim]Br/AlCl₃, in high yield and short reaction time is reported.     

DG and hp-DG for highly indefinite Helmholtz problems

We develop a stability and convergence theory for a Discontinuous Galerkin formulation (DG) of a highly indefinite Helmholtz problem in . We prove that the DG-method admits a unique solution under much weaker conditions than for conventional Galerkin methods. It is shown that for the case of hp-DGFEM the optimal convergence order estimate can be obtained under the conditions that is sufficiently small and the polynomial degree p is at least O(log k). (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)