Current Organic Chemistry - Volume 22, Issue 4, 2018

2-Alkynoates are important unsaturated carbonyl compounds showing a large application as intermediates in organic synthesis. Despite wide importance of these compounds in synthetic chemistry, very few synthetic methods have been reported till date. In recent years much effort has been made to develop the carboxylative coupling of terminal alkynes, organohalides and carbon dioxide to provide the 2-alkynoate derivatives. Good yields, high atom and step economy, and readily available substrates are the key features of this page of 2-alkynoate synthesis. This review article is an attempt to survey literature describing synthetic methods for the preparation of 2-alkynoate derivatives through the three-component reaction of terminal alkynes, organohalides and CO2.

Background: This review updates the field of enantioselective organocatalytic Michael reactions performed in aqueous media, covering the literature since the beginning of 2013. Conclusion: From a green chemistry perspective, this review shows that significant efforts have been recently devoted to the development of these reactions in water and in aqueous media.

Background: For more than one hundred years, it has been known that some 2- isoxazolines can be experimentally obtained by the addition of hydroxylamine or its derivatives to α,β-unsaturated carbonyl compounds. Methodology: General methods for the formation of 2-isoxazolines have not been formulated yet. Conclusion: This review will attempt to summarize the numerous published experimental facts on the addition of hydroxylamine or its derivatives to unsaturated carbonyl compounds and analyze these facts in the hope of proposing reaction pathways compatible with the all the experimental data.

Amphiphilic co-networks are a new class of hydrogels that contain both hydrophobic and hydrophilic polymer chains in their structures. So, they have significant properties and great applications in tissue engineering, drug delivery systems, contact lenses, wound dressing, biosensor, and catalyst support. Various strategies have so been developed for the synthesis of amphiphilic co-network, such as ionic or free radical reaction of monomers, and chemical combination of prepolymers. Click combination between hydrophilic and hydrophobic prepolymers is one of the best methods because click reactions are fast, general, and high-yielded. In this paper, we have focused on Cu catalyzed Azidealkyne cycloaddition and thiol-ene reactions because they were used more than other kind of click reactions in amphiphilic co-network synthesis. Additionally, suitable reagents and solvents have been discussed for each type of reactions and ultimately, physical properties of amphiphilic co-networks such as the degree of swelling in aqueous and organic solvents and proper applications of them have also been reviewed.

Background: Phenol is one of the toxic and persistent organic pollutants, usually present in industrial wastewaters originated from petrochemical, coal, and olive mill processing industries. Dephenolization of phenol-laden industrial wastewater is a necessary requirement before discharge into open environment. Remediation using microorganisms or bioremediation is well thought-out as one of the sustainable methods for decontamination of phenol. However, high phenol concentrations rigorously lower the efficiency of microbial phenol degradation. This is due to substrate inhibition and low growth rate. Thus, there is a need of suitable microbial strain(s) which can effectively degrade such high phenol concentrations. Objective: Numerous microbial strains have been reported for phenol degradation but there are comparatively limited reports on degradation of higher phenol concentrations (>1000 mg L-1) and microbial applicability in dephenolization of real industrial wastewaters. In this review, an overview of microbial phenol degradation is presented with major emphasis on aerobic degradation using bacterial strains. Different methods for improving/enhancing the phenol degradation rate, effects of various physico-chemical factors on degradation process, and mechanisms of degradation form the core of the review. A section on applicability of microbial strains in dephenolization of industrial wastewater and major hurdles encountered during the application process is also highlighted in the study.

This review describes the chemistry of 1,2,5- and 1,4,5-thiadiazepines. The investigated heterocycles are monocyclic and fused 1,2,5- and 1,4,5-thiadiazepines. The different sections cover: structural elucidation "spectroscopy", reactivity of substituents attached to ring carbon and nitrogen atoms, synthesis of monocyclic and fused heterocycles incorporated 1,2,5- and 1,4,5-thiadiazepine moiety. Nitrogen and sulfur atoms of thiadiazepine ring system have the ability to donate the electrons pairs in order to form coordination bonds forming different complexes. The aim of this review is to discuss the chemistry of title compounds up till now. The reaction mechanisms are described and discussed, as well as, the biological applications of the target compounds.

Background: Formation of Self-assembled monolayers (SAMs) is one of the most widely used methods to modify a surface to achieve the desired property. It is a very unique, yet simple method to produce highly ordered and stable monolayer on the surface. Adsorption of alkyl thiol to gold or other metal surface is one of the most commonly used methods for the SAM preparation. Biotin is a small molecule used extensively for labeling in biochemical research including bio-assays and biosensors, due to its strong affinity to proteins avidin (Ka~10¹⁵ M^-1) and streptavidin (Ka~10¹³ M^-1). Objective: Biotin-functionalized-PEG-PE-thiol linker is particularly useful for these studies carried out on surfaces. Current methods to synthesize biotinylated PEG-alkyl thiol linker are tedious because of the different reactive intermediate compounds involved in the process. We wanted to develop an alternative high-yielding synthetic route for the synthesis. Results: Here we report a scheme with improved yield for the synthesis of biotinylated PEG-alkyl thiol using the Traceless Staudinger Ligation. The synthesis can be carried out in large scale, making the process beneficial for industrial purposes. In-situ deprotection of the acetylated thiol allows simultaneous adsorption on a gold surface, resulting in stable, coordinated biotinylated monolayer. Monolayer formation was characterized by Fourier transform infrared spectroscopy (FTIR), contact angle and thickness measurement.