Mini-Reviews in Organic Chemistry - Volume 17, Issue 1, 2020

This mini-review will present the recent applications of Tert-Butyl Nitrite (TBN) in organic synthesis. Due to its unique structural feature and wide application, TBN holds a prominent and great potential in organic synthesis. The applications of TBN in three areas viz. aerobic oxidation, annulation, and diazotization were reviewed recently; now, the current mini-review will describe the studies carried out to date in areas such as nitration of alkane, alkene, alkyne, and aromatic compounds, nitrosylation and sequential nitrosylation reactions, using TBN as source of oxygen and nitrogen. The mechanisms of these transformations will be briefly described in this mini-review.

Aryl-aryl bond formation is one of the most important tools in modern organic synthesis. Therefore, there is a high level of interest to develop green, effective reaction system to obtain biaryls. This review summarized the recent advances in the metal-catalyzed Ullmann reaction in which the aryl-aryl bond was formed directly. Furthermore, different types of catalytic mechanisms, especially the surface reaction, have been summarized to help the design of the catalyst.

Dimethylformamide acetals and Bredereck’s reagent (tert-butoxy-bis(dimethylamino) methane) are versatile C1 building blocks due to their ability to undergo condensation reactions with CH-acidic methyl and methylene moieties. Subsequent modulation of the resulting condensation products enables the preparation of open-chain products like aldehydes, ketones, enones, enol ethers, methyl groups, and, most important in alkaloid total synthesis, the annulation of heterocyclic rings like pyridines, pyridine-N-oxides, bromopyridines, aminopyridines, aminopyrimidines, pyrroles and chromenones. In certain cases, these reagents can act as alkylating agents. The applications of these building blocks in natural products total synthesis are reviewed here.

MaxiPostTM is an interesting 3-fluorooxindole derivative, discovered in the late nineties of the last century as potassium channel opener. Since then, two different research fields were discovered: the discovery of new synthetic methods, especially asymmetric ones, and the in vitro and in vivo tests for its use as a drug for different diseases. This mini-review aims to summarize the state of art in both fields.

A variety of processes were reported for efficient removing of heavy metal from wastewater, including but not limited to ion exchange, reverse osmosis, membrane filtration, flotation, coagulation, chemical precipitation, solvent extraction, electrochemical treatments, evaporation, oxidation, adsorption, and biosorption. Among the aforementioned techniques, adsorption/ion exchange has been known as a most important method for removing heavy metal ions and organic pollutants due to great removal performance, simple and easy process, cost-effectiveness and the considerable choice of adsorbent materials. Nanotechnology and its applications have been developed in most branches of science and technology. Extensive studies have been conducted to remove heavy metal ions from wastewater by preparation and applications of various nanomaterials. Nanomaterials offer advantages in comparison to other materials including an extremely high specific surface area, low-temperature modification, short intraparticle diffusion distance, numerous associated sorption sites, tunable surface chemistry, and pore size. In order to evaluate an adsorbent, two key parameters are: the adsorption capacity and the desorption property. The adsorption parameters including the absorbent loading, pH and temperature, concentration of heavy metal ion, ionic strength, and competition among metal ions are often studied and optimized. Several reviews have been published on the application of Graphene (G), Graphene Oxide (GO) in water treatment. In this minireview, we attempted to summarize the recent research advances in water treatment and remediation process by graphene-based materials and provide intensive knowledge of the removal of pollutants in batch and flow systems. Finally, future applicability perspectives are offered to encourage more interesting developments in this promising field. This minireview does not include patent literature.

Beer, one of the most commonly consumed alcoholic beverages, is rich in polyphenols and is the main dietary source of xanthohumol and related prenylflavonoids. However, to avoid haze formation caused by the interaction between polyphenols and proteins, most phenolic compounds are removed from beer and lost in the brewery waste stream via polyvinylpolypyrrolidone (PVPP) adsorption. This waste stream contains several polyphenols with high antioxidant capacity and pharmacological effects; that waste could be used as a rich, low-cost source of these compounds, though little is known about its composition and potential attributes. This work aims to review the polyphenols present in this brewery waste stream, as well as the health benefits associated with their consumption.

Solanesol has antibacterial, anticancer, anti-inflammatory and antiulcer biological activities, and is a key intermediate in the synthesis of coenzyme Q10, vitamin K2, and the anticancer synergist N-solanesyl-N,N'-bis(3,4-dimethoxy-benzyl)ethylenediamine (SDB) and other ubiquinone drugs. Due to its unique chemical structure, the chemical synthesis of solanesol is difficult, so solanesol is currently mainly isolated from solanaceous plants. Tobacco (Nicotiana tabacum) has the highest content of solanesol compared to other solanaceous plants. Currently, the research on the extraction of solanesol from tobacco focuses on its extraction and purification. This article reviews the extraction methods, saponification, separation and purification methods of solanesol, as well as the research progress on tobacco solanesol, in China and abroad in recent years. Studies show that the organic solvent extraction method is time-consuming and has a low extraction rate. Modern technology- assisted extraction methods, such as ultrasound-assisted extraction, microwave-assisted extraction, and supercritical carbon dioxide (CO2) extraction not only can improve the extraction rate but also can effectively shorten the extraction time. The separation and purification of solanesol from the extracting solution are critical steps to meet the purity requirements of synthetic drugs, and are also key in limiting the large-scale industrial production of high-purity solanesol. Molecular Imprinting Technology (MIT) has the advantages of small investment, simple operation and ease of large scale production compared to chromatographic methods. Solanesol separated by MIT can meet the requirements for synthesizing coenzyme Q10. Nowadays, the synthesis of molecularly-imprinted solanesol polymers with better adsorption efficiency is one of the important directions in the future research of solanesol purification.