Current Organic Chemistry - Volume 25, Issue 16, 2021

Aliphatic secondary and tertiary amines are widely used in the production of pharmaceuticals, agrochemicals, dyes, surfactants and rubber chemicals. Most traditional synthetic methods are often unsuitable for large-scale production due to poor selectivity, harsh reaction conditions and the cost of starting materials. In this context, hydroaminomethylation (HAM) is a very attractive catalytic process with high atom economy that starts from inexpensive reagents, such as alkenes. This review aims to provide an updated overview of hydroaminomethylation as a useful tool for synthesizing aliphatic secondary and tertiary amines. Therefore, the discussion will focus on both unsaturated starting compounds and the amines obtained by this one-pot reaction.

Nowadays, boron-containing compounds have gained researchers’ attention because of the wide versatility and applicability of this element in both organic and medicinal chemistry. Since its discovery, its use in medicinal chemistry was neglected because of its possible toxic effects. However, in the past years, boron-containing compounds did not show such effects, and some drugs have already been approved by the Food and Drug Administration to treat diseases, including cancer, infections, and inflammation. Several boroncontaining compounds are used in organic and medicinal chemistry, either as a reagent or therapeutic agent. The chemical properties of this element make its use possible in organic synthesis as a reducing agent and catalyst, mainly in cross-coupling reactions. Among boroncontaining compounds, boranes, azaborines, benzoxaborole, boronic acid, and boron derivatives are most commonly described. This review article discusses the main properties of boron-containing compounds, their preparation by organic synthesis, as well as their applications in organic synthesis and medicinal chemistry fields, developing new perspectives for further investigations.

Aziridines are the saturated three-membered cyclic amines that constitute an important group of synthetic intermediates. These could act as a precursor for diverse organic compounds owing to the reactivity due to the ring strain associated with them. The outstanding property of aziridines is their high reactivity towards various nucleophilic and electrophilic reagents to acquire more stable ring-opened or ring-expanded amines that could be obtained from the release of strain energy intrinsic in a small ring. As such, aziridines could be used in the synthesis of 4-7 membered heterocycles of biological and industrial significance, such as azetidines, imidazoles, thiazoles, pyrazines, pyrimidines, benzothiazines, benzodiazepines, etc. Earlier synthesis of aziridines was considered a laborious task due to their instability. However, various synthetic approaches leading to the formation of aziridines are now available in the literature. Recently, green, cost-effective and approaches based on simpler work-up for these reactions have attracted researcher's attention. This review article deals with synthetic routes of aziridines and aziridine applications in organic synthesis.

In the last few decades, urea derivatives have gained significant importance due to its wide applications in pharmaceutical, polymer, dyes, and agriculture industries. Urea derivatives are the key starting material for the synthesis of novel bioactive heterocyclic molecules. Substituted urea derivatives are known to possess a wide array of biological activities such as herbicidal, antimicrobial, antimalarial, antivirus, anticancer, antioxidants, antiproliferative, antiatherosclerotic, anti-inflammatory, antibiotic, sedatives, anticonvulsants and as HIV-1 protease inhibitor. Herein, the synthetic approach and its herbicidal, anticonvulsant, antimicrobial, and antiproliferative activities are reviewed. This review summarizes the current updates about the syntheses and biological behavior of substituted urea.

Cyclodextrin (CD) polymers are covalently linked hollow structures that are a network of less flexible macrocycles. They can be divided into two main groups: a) soluble (CDPS); and b) insoluble (CDPIS) polymers. These two types are generally prepared in a similar reaction, and the CD/reagent ratio determines the final properties of the reaction product. Changing this ratio of the generally bifunctionalized crosslinking agent and reaction conditions can lead to CDPS or CDPIS. The classical synthetic way in solution often leads to partial reagent(s) degradation, which frequently results in poorly reproducible products. At the same CD/reagent ratio, the reaction in solution yielded soluble CD polymers, whereas the reaction under mechanochemical conditions produced insoluble CD polymers. Usually, further derivatization of CDPIS or polymerization of derivatized CDs can be difficult or even impossible. The reactivity of hydroxyl groups in methylated CDs is limited so that reactions generally require high-boiling solvents and/or a large excess of reagent. This paper presents an economical, reproducible, and well-scalable synthetic method for producing some insoluble CD polymers. The physicochemical and adsorption properties of CDPIS prepared in a planetary ball mill are also compared.