Given its ready availability, low price and environmentally friendly character, iron is an attractive and often advantageous alternative to other transition metals in the field of catalysis. This tutorial review summarises recent progress in the development of novel and practical iron-catalysed reactions with a particular focus on those which provide access to new carbon-heteroatom and heteroatom-heteroatom linkages. It shall be of interest for both the academic as well as the industrial community.
Non‐covalent molecular interactions on the basis of halogen and chalcogen bonding represent a promising, powerful catalytic activation mode. However, these “unusual” non‐covalent interactions are typically employed in the solid state and scarcely exploited in catalysis. In recent years, an increased interest in halogen and chalcogen bonding has been awaken, as they provide profound characteristics that make them an appealing alternative to the well‐explored hydrogen bonding. Being particularly relevant in the binding of “soft” substrates, the similar strength to hydrogen bonding interactions and its higher directionality allows for solution‐phase applications with halogen and chalcogen bonding as the key interaction. In this mini‐review, the special features, state‐of‐the‐art and key examples of these so‐called σ‐hole interactions in the field of organocatalysis are presented.
The synthesis of a variety of substituted quinolines from N-alkyl anilines by a one-pot dehydrogenative Povarov/oxidation tandem reaction with mono- and 1,2-disubstituted aryl and alkyl olefins was developed. A simple protocol using cheap and benign iron(III)chloride as the Lewis acid catalyst and a TEMPO oxoammonium salt as a nontoxic, mild, efficient oxidant is reported.
Amino acids and peptides play an important role in nature, as well as in organic and pharmaceutical chemistry. Therefore, the easy, straightforward and versatile access of biogenic and unnatural derivatives is still highly demanding. This micro‐review intends to provide to the reader the current state of the art on site‐selective C–H bond functionalization technology applied on α‐amino acids and peptides, focusing on the different C–H positions that can successfully be addressed to date. It is structured in two main parts implying i) the α‐C–H functionalization at the peptide backbone and ii) the modification of the side‐chain. Herein, metal‐catalyzed C–H activation, oxidative C–H functionalization, as well as light mediated approaches, are discussed considering the challenges in reactivity and selectivity. The great potential of these transformations is also depicted with the derivatization and macrocyclization of complex peptides leading to products of pharmaceutical importance.
Helical chirality and selective anion-binding processes are key strategies used in nature to promote highly enantioselective chemical reactions. Although enormous efforts have been made to develop simple helical chiral systems and thus open new possibilities in asymmetric catalysis and synthesis, the efficient use of synthetic oligo- and polymeric helical chiral catalysts is still very challenging and rather unusual. In this work, structural unique chiral oligotriazoles have been developed as C-H bond-based anion-binding catalysts for the asymmetric dearomatization of N-heteroarenes. These rotational flexible catalysts adopt a reinforced chiral helical conformation upon binding to a chloride anion, allowing high levels of chirality transfer via a close chiral anion-pair complex with a preformed ionic substrate. This methodology offers a straightforward and potent entry to the synthesis of chiral (bioactive)heterocycles with added synthetic value from simple and abundant heteroarenes.
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