Letters in Organic Chemistry - Volume 16, Issue 11, 2019

Today, the chicken egg is consumed worldwide with an annual production on the order of tons. However, in spite of its importance, problems include the generation of waste due to its shell, which is composed of calcium carbonate (CaCO3). The application of eggshell waste can be utilized in different fields, such as chemistry, due to its potential possibilities in different types of chemical reactions. In this context, the aim of this review is to demonstrate the versatility and applications of this waste over the last five years in different kinds of chemical reactions.

A novel copper(I)-mediated trifluoroacetylation of anilines with ethyl trifluoropyruvate as a trifluoroacetylating reagent has been developed. Although this protocol could provide good yields in most cases, the reaction exhibited the obvious electronic and steric effects of substituents. The trace amount of products was only obtained for the substrates with ortho-substituted or electron-deficient groups.

A recyclable, eco-friendly, efficient method of synthesis has been developed for the biologically active heterocycles pyranoquinolines and furanoquinolines via inverse electron demand Diels- Alder reaction mediated by choline chloride: zinc chloride ionic liquid as a catalyst and medium. The methodology offers the advantages such as mild reaction conditions, simple work-up procedure, highly efficient reaction, recyclable and eco-friendly catalyst etc. All the products were thoroughly characterized by FT-IR, 1H-NMR, 13C-NMR, Mass spectral and Elemental analysis.

The paper describes the synthesis of quinoline-4-carboxylic acid derivatives employing completely green methods such as the use of water as solvent and of microwave irradiation for heating. The prepared molecules were examined for bactericidal and antifungal behavior and two of the tested compounds showed reasonably good antimicrobial activity. The biological activity results were further corroborated by fluorescence microscopy and by evaluating their time-dependent bactericidal behavior. Two of the most potent compounds were then subjected to docking against DNA gyrase protein (PDB ID: 2XCT) showing possible interactions responsible for the potency of these compounds. Also, an SAR analysis was proposed based on the results obtained.

Novel aza-heterocyclic substituted dehydroepiandrosterone derivatives were synthesized through a three-step reaction sequence. Some new O-alkylated 4-hydroxybenzaldehydes were synthesized from the reaction of substituted benzaldehydes with dihalogen compounds which have different chain lengths. 16-Arylidene steroids were synthesized from the base-catalyzed aldol condensation of O-alkylated 4-hydroxybenzaldehydes and dehydroepiandrosterone. New indolyl and benzimidazolyl substituted steroid derivatives as hybrid molecules were obtained from the reaction of 16-arylidene steroids with indole or benzimidazole.

Synthesis of pyrazole-3-carboxylic acid was progressed via two different protocols, one of which is solid state. Pyrazole-3-carboxylic acid was converted into different derivatives such as ester, urea, amide and nitrile. The amide compound was converted to nitrile using SOCl2 and DMF. Solid state heating of carboxylic acid gave decarboxylated product. Cyclization of tetra-substituted pyrazole with hydrazines resulted in pyrazolopyridazinones. The antimicrobial activities of the synthesized pyrazole derivatives against Bacillus cereus, Escherichia coli, Micrococcus luteus, Staphylococcus aureus, and Saccharomyces cerevisiae were evaluated. One of the pyrazole derivatives which possess nitro group showed antimicrobial activity in only B. cereus, a Gram-positive bacteria, with an MIC of 128 μg/mL.

Quinazoline is the six-membered heterocyclic ring system reported for its versatile biological activities. This characteristic feature of quinazoline makes it a good template for a lead generation library. Ring opening is one of the major concerns in the synthesis of quinazolin-4(3H)-one that results in diamide formation. Here, alternative fusion strategy is reported, which is a time-saving and costeffective method to overcome the ring opening problem associated with the synthesis of benzo[ d][1,3]oxazin-4-one and quinazolin-4(3H)-one.

A new series of benzamido alkyl naphthols were synthesized from the multi-component reaction of 4-(3′-methylthioureido)benzamide, aromatic aldehydes and 2-naphthol. Molten tetrabutyl ammonium bromide was used as a very efficient medium for this reaction while the use of common organic solvents gave no or poor yields. This method is an interesting instance of using molten salt as a medium in multicomponent reactions.

This study introduces a concise and efficient method for preparing diacetoxyiodoarenes from the corresponding iodoarenes. In the presence of acetic anhydride, iodoarenes were oxidized to diacetoxyiodoarenes by sodium perborate in acetic acid under argon protection at 55°C in ideal yields. Through this method, 10 diacetoxyiodoarenes were obtained smoothly.

Pyridopyrimidines represent a highly important class of compounds which exhibit a wide spectrum of biological properties. Nanoscale metal oxide catalysts have been extensively studied for their application in organic reactions owing to their special features such as high surface area and pore sizes as supports. Titanium dioxide nanoparticles (TiO2 NPs) are an attractive candidate for readily available cheap nanocatalysts, due to their unique properties such as being non-toxic, moisture stable and reusable catalyst. 7-amino-2,4-dioxo-5-aryl-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-6-carbonitriles were synthesized through the reaction of 4(6)-aminouracil, aromatic aldehydes, and malononitrile using calcined TiO2-SiO2 nanocomposite as a reusable catalyst in water at ambient temperature. All the synthesized compounds were well characterized by their elemental analyses, IR, 1H and 13C NMR spectroscopy. The synthesized catalyst was fully characterized by the powder X-ray diffraction (XRD), the scanning electron microcopy (SEM), the transmission electron microscopy (TEM), and the x-ray fluorescence (XRF) techniques. The reaction proceeded through calcined TiO2-SiO2 nanocomposite catalyzed three-component reaction affording twelve target compounds in high yields. This method introduced a novel protocol to provide 7-amino-2,4-dioxo-5-aryl-1,2,3,4-tetrahydropyrido[2,3- d]pyrimidine-6-carbonitrile derivatives and offer several advantages like very simple operation, using inexpensive, recyclable and non-toxic catalyst, mild reaction conditions, high yields of products (92- 98%), short reaction times (2.5-4 h), and green aspects by avoiding toxic catalysts and hazardous solvents.

An expeditious three-component synthesis of various biologically important heterocyclic compounds 5-amino-1,3-diaryl-1H-pyrazole-4-carbonitriles by condensation of aryl aldehydes, malononitrile and phenylhydrazine derivatives is described. This greener protocol was catalyzed by L-Proline and proceeded efficiently in solvent at room temperature within 2-15 min.