Mini-Reviews in Organic Chemistry - Volume 16, Issue 4, 2019

In recent years, a very interest in the synthesis of functionalized 3-thioxo-1,2,4-triazin-5- ones and their derivatives as vital probes has been increased, due to the important, applications of the medicinal, pharmacological, and biological field as a drug, semi drug, and bioactive systems. The present work review outlines extensive recent advances literature survey on the synthesis of sulfurbearing 1,2,4-triazin-5-one derivatives has been reconsidered. Also, the behavior of these family towards electrophilic and nucleophilic reagents in different media and conditions reported. The biological evaluation of the most synthesized systems included anticancer, anti-HIV, antimicrobial as well as their enzymatic effects (cellobiase produced by fungi) have been reported. The reactivity of these systems depends on the polarity of solvent, temperature, molarity as well as a type of tautomeric present.

This review covers recent approaches to the synthesis of tertiary phosphines through the C– PR2 (R = alkyl or aryl) bond formation reactions using palladium. The methods include Pd-catalyzed additions of HPR2 to double and triple bonds, substitution and dynamic kinetic resolution of diaryl (pseudo) halide compounds, reactions of cyclopalladated complexes with MPR2 (M = Li or K) or HPR2, intramolecular phosphination, and C–P⁺ bond cleavages. Together these methods allow for the preparation of diversely functionalized achiral or enantiopure tertiary phosphines for use in organo- and transition metal catalysis among other important applications.

With the development of industry, urbanization, increasingly stringent environmental protection requirements, and strengthening of people’s environmental awareness, green treatment of pollutants has become a research hotspot in the field of environmental protection. Accordingly, the study on natural non-toxic polymers has received increasing attention from researchers. This paper aims to provide the present research progress of natural polymers in environmental engineering, including the striking characteristics and modification methods of the most well-known natural polymers, as well as their applications in environmental protection field. Concluding remarks and future trends are also pointed out.

Lignin is a natural polymer composed primarily of phenylpropanoid structures with an abundance of reactive groups: aliphatic and aromatic hydroxyls, phenols, and carbonyls. Considering the large quantity of hydroxyl groups, lignin has significant potential as a replacement for petroleum-based polyols in polyurethane (PU) synthesis and as a value-added, renewable raw material for this purpose. Several methods of lignin-based polyurethane synthesis are reviewed in this paper for reactive and thermoplastic systems: direct lignin incorporation, chemical lignin modification and depolymerization. Despite the unmodified lignin low reactivity towards diisocyanates, its direct incorporation as polyol generates highly brittle PUs, but with proper performance when applied as adhesive for wood. PU brittleness can be reduced employing polyols obtained from lignin/chain extender blends, in which glass transition temperature (Tg), mechanical properties and PU homogeneity are strongly affected by lignin content. The potential applications of lignin can be enhanced by lignin chemical modifications, including oxyalkylation and depolymerization, improving polyurethanes properties. Another PU category, lignin- based thermoplastic polyurethane (LTPU) synthesis, emerges as a sustainable alternative and is also presented in this work.

This review article represents a survey of the synthetic strategies leading to pyrazolyl quinolines. The synthetic methods are divided into two main groups based on the type of starting reagents: 1) From quinoline ring onto a pyrazole scaffold, 2) From pyrazole ring onto a quinoline scaffold. Also, some medical applications of pyrazolyl quinoline derivatives are mentioned such as anticancer, cell proliferative disorder, glucose transport inhibitors, anti-inflammatory, and inhibitors of leukotriene production for the treatment of cardiovascular. The main purpose of this review is to present a survey of the literature on the synthetic approaches of pyrazolyl quinolines and provide useful and up-to-date data for organic and medicinal chemist since such compound has not been previously reviewed.

Propargylamines are prominent components strikethrough as precursors for the synthesis of miscellaneous nitrogen-containing compounds, such as allylamines, pyrrolidines, pyrroles and oxazoles or as intermediates in the preparation of a various natural product, biologically active and pharmaceutical compounds. The catalytic coupling of the aldehyde–alkyne–amine (A3 coupling) has shown great utility in the simple and rapid preparation of propargylamines in broadly tolerant and highly tunable reaction conditions. In this respect, various catalytic systems using transition metal catalysts have been developed. Based on a literature survey, Cu catalysts have promoted this field substantially via development of new methods for the synthesis of propargylamines. This review will cover copper-based catalyst system reported for the synthesis of propargylamine derivatives until 2017.

Industrial effluents containing heavy metals can have harmful effects on organisms and the ecosystem. Silver is a waste from textile, galvanic and photographic industries, and when released into the environment, it can harm human health and cause biological modification. Removal of metals, such as silver, has been traditionally carried out using physicochemical methods that produce a high concentration of sludge and expend a significant amount of energy. Researchers are seeking innovative technologies for more efficient removal of silver or for using this heavy metal to obtain new products. The use of microalgae is a promising alternative to traditional remediation methods because several species can absorb and assimilate heavy metals. When exposed to toxic substances, microalgae excrete molecules in the medium that induce the reduction of silver particles to nanoparticles. Biosynthesized silver nanoparticles (AgNPs) can be used in medicine, food packaging, the production of cosmetics and pharmaceuticals, civil engineering, sensors and water purification. Thus, microalgal biosynthesis of metal nanoparticles has the capacity to bioremediate metals and subsequently convert them into non-toxic forms in the cell. In this context, this review addresses the use of microalgal biotechnology for industrial waste remediation of silver, which includes the simultaneous biosynthesis of AgNPs. We also discuss the potential applications of these nanoparticles.

Flavonoids constitute a large group of polyphenolic compounds that are known to have antioxidant properties, through their free radical scavenging abilities. They possess a chromone (γ- benzopyrone) moiety, responsible for eliciting many pharmacological activities. Even though, natural flavonoids are highly potent, owing to their poor solubility, they are less used. Therefore, attempts have been made to improve their stability, solubility, efficacy and kinetics by introducing various substituents on the flavone ring. For nearly the last two decades, flavones were synthesized in our laboratory by simple, convenient and cost-effective methods, with the knowledge of both synthetic and semi-synthetic chemistry. In this direction, it was considered worthwhile to present an overview on the synthesized flavonoids. This review creates a platform for highlighting various modifications done on the flavone system along with their biological activity.

Optically pure 1,1′-bi-2-naphthol (BINOL) and its derivatives are among the most widely used chiral ligands and auxiliaries for asymmetric synthesis. These molecules also occur as scaffolds for various biologically active compounds. Direct oxidative coupling of 2-naphthols in the presence of chiral catalysts provides a powerful strategy for the synthesis of optically pure 1,1′-bi-2-naphthols (BINOLS). In 1978, Wynberg with co-workers discovered that a copper salt with chiral auxiliary mediates the oxidative coupling of 2-naphthols, which can be taken as the starting point for further progress in this area. Over the last decades, a number of efficient and stereoselective catalyst systems have been developed. This mini-review surveys the aerobic asymmetric oxidative coupling of 2-naphthols catalyzed by transition metal complexes reported since 1995.

A review of the technological principles of the production of alkyd resins modified with vegetable oils has been presented. Reactions and transformations occurring during the crosslinking in the presence of unsaturated fatty acids and mono-, di- and triglycerides have been described. Influence of the addition of other resins to modified glyptals and pentaphthalates have been presented. Research trends indicate the growing importance of nanomaterials in the preparation of alkyd coatings with improved properties.