An efficient one‐pot synthesis of pyridazinones and phthalazinones using HY‐zeolite

The first one‐pot synthesis of pyridazinones and phthalazinones from arenes, cyclic anhydrides, and ArNHNH₂ in the presence of efficient recyclable heterogeneous catalyst, HY‐zeolite, in high yield and short reaction time is reported. J. Heterocyclic Chem., (2011).     

Melamine–formaldehyde resin supported H a mild and inexpensive reagent for synthesis of coumarins under mild conditions

Melamine-formaldehyde resin supported H~+ is used as an efficient catalyst in the Pechmann condensation reaction of phenols withβ-ketoesters,in solvent-free media leading to the formation of coumarin derivatives using conventional heating and microwave irradiation in excellent yields with good purity.     

Characterizing Semigroups by Sequentially Dense Injective Acts

Sequentially dense monomorphisms and injectivity with respect to these monomorphisms were first introduced and studied by Giuli for acts over the monoid (N^∞, min). In this paper we generalize these notions to acts over a general semigroup, and study the behaviour of this notion of injectivity with respect to products, coproducts, and direct sums. As a result we give some characterizations of semigroups.     

The reaction of Wittig and Wittig–Horner reagents with dicyanomethylene derivatives of fluorenone,xanthone, and thiaxanthone. A novel synthesis of phosphoranylidenecyclobutylidene derivatives

>Wittig reagents 1a,b react with dicyanomethylene derivatives of fluorenone (3) and xanthone (4) to give the corresponding phosphoranylidenecyclobutylidene adducts 6a, 6b, 9a, and 9b. On the other hand, the reaction of Wittig–Horner reagents (2) with the same nitriles 3 and 4 afforded the respective phosphonate adduct 8 and the alkylated product 10. A mechanism that accounts for the formation of the new products is presented. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 263–269, 1999     

Effect of Non-Calcined Sugarcane Bagasse Ash as an Alternative Precursor on the Properties of Alkali-Activated Pastes

BFS-MK-based alkali-activated materials are well established as an alternative for sustainable and green construction. This work aims to collaborate and encourage the use of biomass ashes, such as sugarcane bagasse ash (SCBA), as a precursor in alkali-activated materials (AAM). This ash is a rich source of aluminosilicate, which is a primary requirement for this application. In addition, this waste is still an environmental liability, especially in developing countries, and with a large volume of annual production. Thus, in this research, alkali-activated pastes (AA) were produced using sugarcane bagasse ash (SCBA), granulated blast furnace slag (BFS) and metakaolin (MK) as precursors. In addition, environmental gains were encouraged with energy savings, with no extra reburn or calcination steps in the SCBA. Thus, the precursors were characterized by laser granulometry, X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The pastes were produced by mixing the precursors with the activator, composed of a mixture of sodium hydroxide 8 mol/L and sodium silicate. Aiming to study the incorporation of SCBA, all samples have a precursor/activator ratio and a BFS/(BFS + MK) ratio constant of 0.6. The compressive strength analysis, FTIR, XRD, TGA, SEM and isothermal calorimetry analyses pointed out the occurrence of alkaline activation in all proposed samples for curing times of 7, 28 and 91 days. The sample GM0.6-BA0 (15% SCBA) achieved the highest compressive strength among the samples proposed (117.7 MPa, at 91 days), along with a good development of strength throughout the curing days. Thus, this work presents the properties of alkaline-activated pastes using SCBA as a sustainable and alternative precursor, seeking to encourage the use of raw materials and alternative waste in civil construction.     

Highly selective and sensitive copper(II) membrane coated graphite electrode based on a recently synthesized Schiff’s base

A PVC membrane electrode based on bis-2-thiophenal propanediamine (TPDA) coated directly on graphite is described. The electrode exhibits a Nernstian response for Cu²⁺ over a very wide concentration range (1.0×10⁻¹ to 6.0×10⁻⁸ M) with a detection limit of 3.0×10⁻⁸ M (2.56 ng ml⁻¹). It has a fast response time and can be used for at least 2 months without any major deviation. The proposed sensor revealed very good selectivities for Cu²⁺ over a wide variety of other metal ions and could be used in the pH range of 3.0–7.0. It was successfully used for direct determination of copper in black tea and as an indicator electrode in potentiometric titration of copper ion.     

Elegant Synthesis of Highly Functionalized 1,2,3-Trisubstituted Cyclopentanes

The conversion of cyclic Baylis–Hillman acetates 1 into the corresponding cyano derivatives 2 was achieved using potassium cyanide in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) in aqueous medium. The obtained Michael acceptors 2 easily add primary amines in absolute ethanol to produce a new family of 1,2,3-trisubstituted cyclpentanes 3 in good yields.     

New poly(ester amide ether amide)s from a novel flexible diamine and different diacid chlorides using TMSCl for in situ silylation

A novel flexible diamine with built-in ester, amide and ether groups named terephthalic acid bis(4-{2-[2-(2-amino ethoxy)ethoxy]ethyl carbamoyl}phenyl) ester (TABE), was synthesized via two steps. Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride in the presence of NaOH yielded terephthaloyl bis (4-oxybenzoic) acid (TOBA). The diamine (TABE) was prepared via two direct and indirect methods. In the indirect method TOBA was converted to related diacid chloride and reacted with 1,8-diamino-3,6-dioxaoctane (DADO). Direct method was achieved through the reaction of TOBA with DADO via Yamazaki method. TOBA and TABE were fully characterized and TABE was used to prepare new poly(ester amide ether amide)s through polycondensation with different diacid chlorides in the presence of trimethylchlorosilane (TMSCl). The polymers were characterized using conventional methods and their physical properties including inherent viscosity, thermal behavior, thermal stability, crystallinity, and solubility were studied. The polymers showed good thermal stability and improved solubility.     

Poly(sulfone ether amide amide)s as a new generation of soluble, thermally stable polymers

A new sulfone ether amide diamine was synthesized via three steps, starting from reaction of 4-aminophenol with 4-nitrobenzoyl chloride in the presence of propylene oxide afforded N-(4-hydroxy phenyl)-4-nitrobenzamide (HPNB). In the next step, reduction of nitro group resulted in preparation of 4-amino-N-(4-hydroxy phenyl) benzamide (AHPB). Final step in the preparation of diamine was the reaction of AHPB with bis(4-chlorophenyl) sulfone in the presence of K₂CO₃. All the materials were characterized using conventional spectroscopic methods. Poly(sulfone ether amide amide)s were synthesized by polycondensation reactions of prepared diamine with different diacid chlorides (aromatic and aliphatic ones). The obtained polymers were fully characterized and their physical properties including thermal behavior, thermal stability, solubility, and inherent viscosity were studied.