Amides are undeniably some of the most important compounds in Nature and the chemical industry, being present in biomolecules, materials, pharmaceuticals and many other substances. Unfortunately, the traditional synthesis of amides suffers from some important drawbacks, principally the use of stoichiometric activators or the need to use highly reactive carboxylic acid derivatives. In recent years, the transamidation reaction has emerged as a valuable alternative to prepare amides. The reactivity of amides makes their direct reaction with nitrogen nucleophiles difficult; thus, the direct transamidation reaction needs a catalyst in order to activate the amide moiety and to promote the completion of the reaction because equilibrium is established. In this review, we present research on direct transamidation reactions ranging from studies of the mechanism to the recent developments of more applicable and versatile methodologies, emphasizing those reactions involving activation with metal catalysts.

Iron is an indispensable element for the development of almost all living things, and its acquisition is a key process for organisms. However, the low solubility of Fe3+ in aqueous systems causes its reduced bioavailability. Thus, organisms confronted with low iron availability have developed several iron scavenging strategies, and one of these ways is to use low molecular‐weight organic molecules, which are specific ferric ion chelators called siderophores. These compounds exhibit an extremely high affinity and specificity for Fe3+ and are produced and secreted by bacteria, fungi, and plants. Recently, siderophores have attracted much attention due to their applications in areas such as microbial ecology, specific crop production, detoxification of heavy metal‐contaminated samples, biodetection of metals, and the selective delivery of antibiotics to resistant bacterial strains. Nevertheless, the limited supply of these natural products has been an obstacle that needs to be overcome. This review provides an overview of the contemporary developments in the total synthesis of naturally occurring siderophores during the last two decades.

Herein, we describe a selective late‐stage deoxygenation of sulfoxides based on a novel application of chlorosulfonium salts and demonstrate a new process using these species generated in situ from sulfoxides as the source of electrophilic chlorine. The use of highly nucleophilic 1,3,5‐trimethoxybenzene (TMB) as the reducing agent is described for the first time and applied in the deoxygenation of simple and functionalized sulfoxides. The method is easy to handle, economic, suitable for gram‐scale operations, and readily applied for poly‐functionalized molecules, as demonstrated with more than 45 examples, including commercial medicines and analogues. We also report the results of competition experiments that define the more reactive sulfoxide and we present a mechanistic proposal based on substrate and product observations.

The competition between an unprecedented reductive chlorination and the Pummerer reaction was studied and applied to the synthesis of benzofused oxygen heterocycles including 3-aminochromanes and in the intramolecular chlorination of activated aromatic rings. The use of (COCl) 2 as a Pummerer activator showed substantial activity, producing α-chlorinated sulfides that can undergo Pummerer−Friedel−Crafts cyclization. If the aromatic ring has electron-donating groups in position three, then the reaction follows a different pathway, yielding the reductive chlorination products, where the chlorine atom comes from a sulfonium salt.

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