Mini-Reviews in Organic Chemistry - Volume 14, Issue 2, 2017

Background: The canthin-4-ones are a small, yet underexplored class of natural products from Apocynaceae plants. Efficient synthetic approaches are required for exploring this class of natural products for drug discovery. Objective: In this review, the synthetic approaches towards these alkaloids, as well as synthetic analogues are summarized comprehensively. Further, the applications of canthin-4-ones as building blocks for the synthesis of alkaloids and other polycyclic compounds of pharmaceutical interest are demonstrated. Conclusion: Meanwhile, efficient and flexible approaches to the canthin-4-one scaffold are available which should foster in-depth investigation of this chemotype for drug development.

This paper describes the mechanism of nitrogen and phosphorus removal by activated sludge process, and introduces several conventional nitrogen and phosphorus bioremoval processes, namely sequencing batch reactor (SBR), anaerobic-anoxic-aerobic (AAO), oxidation ditch, and bio-doubling process (BDP). Many improved technologies were invented to compensate for the defects of conventional activated sludge process Nitrogen and phosphorus bioremoval by activated sludge process have many similarities and conflicts, including different sludge characteristics and competition for carbon sources that affect the results of the simultaneous nitrogen and phosphorus removal. Therefore, a series of countermeasures to resolve such conflicts are reviewed. Economy, sefficiency and low energy consumption will be the developing trends of wastewater treatment in the future.

Alkynes and cumulenes share the common feature of at least one sp-hybridized carbon atom in the molecule. This leads to the molecules having relatively high energy in the thermodynamic sense, but also having high stability in the kinetic sense. Enediynes, enyne-cumulenes and yne-diynes all undergo pericyclic reactions resulting in cycloaromatization to dehydrobenzenes and related products. In this review, the history, mechanism and synthetic uses of these reactions are discussed.

Recently Fe3O4@silica sulfuric acid as an efficient nanomagnetically recyclable solid acid catalyst has been synthesized and used in organic transformations. Magnetic nanoparticles were synthesized by simple co-precipitation of FeCl2.4H2O and FeCl3.6H2O in ammonia solution. Then, after addition of tetraethyl orthosilicate in ammonia solution, silica was formed on the surface of magnetite nanoparticles. Finally, the catalyst has been prepared by the functionalization of silica-coated magnetic nanoparticles (Fe3O4@SiO2) using chlorosulfonic acid. The catalyst was characterized by Fourier transform-infrared (FT-IR) spectrometry, X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating- sample magnetometry (VSM) and thermo gravimetric analyses (TGA). Nano-Fe3O4@silica sulfuric acid was easily recovered from the reaction mixtures by an external magnet and reused several times with no significant decrease in its catalytic activity. In this review, preparation, characterization and applications of this catalyst in organic synthesis has been discussed.

Recent developments of functionalization of C(sp3)-H bonds adjacent to oxygen of alcohols under metal-free conditions are summarized here. Alcohols are one of the most common and useful chemicals, so the direct functionalization of C(sp3)-H bonds adjacent to oxygen of alcohols is a promising direction in organic synthesis.

The use of microwave irradiation in organic chemistry and, in particular in 1,3-dipolar cycloaddition has recently gained much attention and great progress has been accomplished in this area in the last years. In general, the modern synthetic chemistry is benefited by microwave irradiation that provides an environmentally benign approach, reduced reaction times and a few formation of byproducts, increasing the yield. This review aims to collect recent developments on the synthesis of isoxazolidine compounds by microwave-assisted 1,3-dipolar cycloaddition, considering the absence of a recent review about this specific reaction method. Owing to the large extent of available literature, we have decided to restrict our review to the developments in the last six years, making a selection of the literature from 2010 to 2016. The discussion of several examples to construct isoxazolidines by irradiation of microwave will allow to focus on the advances in the development of microwave-assisted 1,3- dipolar cycloadditions, obtaining a broader vision of the real effects of this reaction methodology on yields, regio- and stereoselectivity of the reaction.

Barbituric acid (pyrimidine-2,4,6(1H,3H,5H)-trione) as odourless white crystals has been prepared in 1864. Due to the acidity of the CH2 group, the pyrimidine ring of barbituric acid could be stabilized via the resonance delocalization, which led it to show potential donor-acceptor properties of the heteroatoms in the molecule. Barbituric acid and its derivatives are versatile moieties in many compounds which possess interesting utility in biology, industry, and drugs. They have been utilized as sedative hypnotics, anticonvulsants, and anaesthetics. Multicomponent reactions play key role in organic and medicinal chemistry. In these types of reactions barbituric acid possess particular position, as a versatile heterocycle, due to its interesting chemical and potent-biological properties. in this report we focused on barbituric acid transformations. The review subdivided with centralization on the solvent presentation. Synthesis of different forms of these scaffolds, by a glance to the reaction media (solventfree conditions, aqueous medium, and organic solvents), have been demonstrated. Solvent-free technique is an environmentally-friendly process in the absence of volatile toxic solvents, which makes it straightly forward to green chemistry. Water as eco-friendly another reaction media with an unusual accelerating effect, which was represented as a systematic phenomenon, could be utilized as a solvent in organic reactions because of its cheapness, safety, and most non toxicity. The review describes the preparation of various heteroaromatic compounds containing barbiturates, which covering the literature relevant up to 2015.