Mini-Reviews in Organic Chemistry - Volume 15, Issue 2, 2018

Catalysis research under bromine is a well-known topic in organic synthesis. However, hazardous and toxic nature of bromine and its negative and deleterious effects on the human health has caused organic chemists to avoid working on bromine. Although, in the last decade, a category of heterogeneous bromine source catalysts (especially N-tribromides) has been introduced to overcome this problem, nevertheless, the recovery and reusability of these catalysts from the desired product or reaction mixture are often a laborious task. In recent times, catalysis research has clearly experienced a renaissance in the area of utility of bromine-containing nano-catalysts based on their ability to recovery and reusability; the activity of these bromine nano-catalysts was investigated in a category of organic reactions. In this review we summarized the obtained results under recoverable bromine-containing nano-catalysts with the goal of stimulating further progresses in this field.

Polyhydroxyalkanoates (PHAs) and other biopolymers vary in their behavior and properties, but are extremely useful in medical applications because of their biodegradability. As long-term problems arise with permanent implants, different biopolymers can be selected and blended to replace the old PHAs and other homopolymers with new, less invasive alternatives. Scaffolds and surgical meshes are not designed to fuse with regrown tissue, but are intended to both guide new tissue and degrade when they are no longer required. The mechanical properties, characteristic length, and degradation profile of scaffold biopolymers are the key concerns in their medical application. Although the PHA and other biopolymers have excessively long degradation times, blending tough polymers with less durable polymers may alleviate the problems. The hydrophobic polymers must be balanced with their cytotoxicity; therefore, additional focus is being placed on changing the surface properties through grafting.

Naratriptan 1 is a selective serotonin 5-hydroxytryptamine 5-HT1 receptor subtype agonist used for the treatment of acute attacks of migraine headaches and for cluster headaches. Since its discovery in 1998 by GlaxoSmithKline, a number of synthetic methods have been reported up till now. This review aims to focus soberly the various synthetic key routes used for the synthesis of naratriptan 1 in high yields. An effort has been carried out to provide an overview of practical, safe and scalable methods for the preparation of naratriptan, describing various Pd-catalyzed Heck reactions, Matsuda– Heck coupling, Fischer indolizations, Sonogashira coupling, Japp-Klingemann reaction and TiCl4- mediated indolization. Moreover, the precursors utilized in the synthesis have been described briefly.

Template polymerization refers to the synthesis of cationic polyacrylamide (CPAM) with microblock structures. The definition of template polymerization and the reaction mechanism of synthesizing CPAM are presented in this paper. The selection of a template for template polymerization is discussed along with the related kinetic problems and the sequence structure of CPAM that is synthesized via template polymerization. The applications of CPAM are also introduced to provide an important basis for future research on its template polymerization.

Background: It is known that squaramides are able to form up to four hydrogen bonds, in which the remarkably rigid four-membered ring system serves as an ideal hydrogen bond donor/ acceptor unit. Because of the unique physical and chemical properties of squaramides, design and synthesis of squaramide-based functional receptors have become a hot topic in recent years. Objective: This paper reviews the recent advance in the synthesis of squaramide derivatives and their applications in the field of anion recognition and transmembrane transport. In addition, the prospects of squaramide derivatives are also briefly described. Conclusion: Potent anion recognition and high anionophoric activity may be achieved due to the strong hydrogen bonding interactions of anions with pre-organized donor hosts.

A generally accepted classification distinguishes semiconductor photocatalysis in type A and type B. The first class comprehends reactions where the primary redox products (radical anions and cations) further evolve giving rise to the final reduced and oxidized species. Type B reactions occur when the primary redox products undergo intermolecular bond formation to addition products. Recently, some photocatalytic reactions have been reported wherein the photocatalytically produced compounds are not the final products. In fact, they react in the solution bulk or catalytically on the surface of the semiconductor with other species thus producing the target compounds. These reactions, hereby reviewed, make explicit the complexity of photocatalysis and remind scientists that, by investigating and proposing mechanistic insights, the concepts of photocatalysis and catalysis or reactions in bulk solution or in adsorbed phase may often overlap and it is useful to analyze them according to an interdisciplinary overview. For the sake of completeness, various examples of type A and B reactions have also been reviewed.