Current Organic Chemistry - Volume 24, Issue 5, 2020

Azetidin-2-ones (β-lactams) and its derivatives are an important group of heterocyclic compounds that exhibit a wide range of pharmacological properties such as antibacterial, anticancer, anti-diabetic, anti-inflammatory and anticonvulsant. Efforts have been made over the years to develop novel congeners with superior biological activities and minimal potential for undesirable side effects. The present review aimed to highlight some recent discoveries (2013-2019) on the development of novel azetidin-2-one-based compounds as potential anticancer agents.

Amidoalkyl-2-naphthol is one of the vital synthetic intermediates which occupy an imperative position in medicinal chemistry due to its amazing biological, pharmacological as well as industrial and synthetic applications. Owing to its diverse pharmaceutical activities, hundreds of scientific literature are available, signifying the efficient synthesis of this intermediate using various catalysts. Most of these literature methods suffer from low yield and harsh reaction conditions that further ignited the researcher to explore for another green catalyst and fresh methodologies. This review summarizes the last five years progress in the catalytic synthesis of 1-amidoalkyl-2-naphthols using various heterogenous, homogenous and nanocatalysts along with their mechanism of action. Various advantages like green synthesis, atom economy, clean reaction profile and catalyst recovery are discussed which facilitate the scientist to probe and stimulate the study on this scaffold. In the end, the catalysts and reactions condition are organized into the tables for swift at a glance understanding of different catalysts used with their yield and time taken for the synthesis.

Natural products have received much attention due to their importance and application. Indolizidine, categorized as an alkaloid, has several biological activities. The synthesis of natural compounds such as indolizidines has attracted much attention from many chemists’ and researchers’ perspectives. There are many areas to be explored in this subject; that is why synthesizing indolizidine 209I and (±)-indolizidine 209B as natural compounds have received much consideration. This review discloses the procedures and methodology to provide (±)-indolizidine 209I and 209B due to the importance of indolizidines.

1,2,3-triazoles are popular heterocycles employed in material sciences and medicinal chemistry as they show antiviral, antibacterial, anti-HIV, antitubercular, and antifungal activities. Triazoles are appealing due to their stability and interesting click chemistry properties. The Cu(I) catalyzed reaction between azides and alkynes affords the 1,4- disubstituted derivative exclusively becoming a useful synthetic tool. However, one of the main drawbacks of the catalyzed reaction is the need to use Cu(I), which is unstable at standard conditions and rapidly oxidizes to the non-active Cu(II). The most common approach when synthesizing 1,4-disubstituted-1,2,3-triazoles is to reduce Cu in situ employing inorganic Cu salts and a reducing agent. The resulting Cu(I) needs to be further stabilized with organic ligands for the reaction to take place. The aim of homogeneous catalysis is to produce a ligand with a dual function both in reducing and stabilizing Cu(I) without interfering in the overall reaction. Instead, heterogeneous catalysis offers more options when supporting Cu on nanoparticles, complexes, and composites yielding the desired 1,2,3-triazoles in most cases without the need of a reducing agent under green solvents such as ethanol and water. The catalytic activity of Ag, Ru, and Ce is also discussed. This review exemplifies how the use of homogeneous and heterogeneous catalysts offers new and green methodologies for the synthesis of 1,2,3-triazole derivatives. The materials supporting Cu show catalytic properties like high surface area, acid-base sites or phase transfer. Although there is no ideal catalyst, Cu remains the most effective metal since it is economical, abundant and readily available.

Organic symmetric disulfides have been broadly studied in various fields such as synthetic intermediates for various organic transformations, agro-chemicals, biochemistry, pharmacological chemistry, industrial polymers, peptidomimetics, self-assembled monolayers (SAMs), etc. Owing to versatile applications, the search and development of efficient, environmentally friendly, mild and inexpensive methods for the preparation of organic disulfides play an important role in the organic functional group transformations. Various aspects of the S–S bond formation are available in some books on organic functional group transformations, as well as two review articles that have been published in the years 2008 and 2014 highlighting the developments of disulfide bond formation using a variety of reagents. However, investigations on new catalytic methods are being regularly reported and new types of disulfides are synthesized. The present review has attempted to systematically summarize recent catalytic advances in the process of S–S bond formation with a major focus since 2014 on highlighting mechanistic considerations, scope, advantages, and limitations. This review does not include patent literature.