Halogen-Induced Controllable Cyclizations as Diverse Heterocycle Synthetic Strategy

Abstract

In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties by generating halonium intermediates, followed by the attack of carbon-containing, nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to give highly functionalized carbocycles and heterocycles. New transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products, according to the difference in the size and number of halogen atoms, have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.

Visible‐Light‐Catalyzed N‐Radical‐Enabled Cyclization of Alkenes for the Synthesis of Five‐Membered N‐Heterocycles

“…[22] Halogenated molecules also have the advantage of being further functionalized. [23] In 2021, Zhang and co-workers proposed a Mn-catalyzed strategy for generating amidyl radicals from N-fluorinated sulfonamides using visible light (Scheme 4). [24] In this work, aliphatic sulfonamides were generated after intramolecular hydroaminations of alkenes with Mn 2 (CO) 10 as the precatalyst and (MeO) 3 SiH as both the Hatom donor and the F-atom acceptor.…”

Asymmetric Synthesis of Halocyclized Products by Using Various Catalysts: A State‐of‐the‐Art Review

“…Halogens improve lipophilicity, membrane permeability and absorption, and blood‐brain barrier permeability in various drug molecules [1] . The structural reorganization of organic molecules has recently piqued the interest of synthetic chemists, and cyclization reactions induced by halogen groups can be used to produce a variety of targets [2–5] . Electrophilic halogen atoms are essential for synthesizing highly functionalized carbocycles and heterocycles.…”

“…Furthermore, the halogen‐induced cyclization strategy prevents the formation of unwanted bimolecular and intermolecular side reactions. The above strategy is beneficial because the halocyclized products can be functionalized further [2] …”

Recent Developments in Enantioselective Organocatalytic Cascade Reactions for the Construction of Halogenated Ring Systems

“…The literature on reactions leading to compounds bearing chiral halogen‐containing centers has been reviewed periodically [32–35] . In 2020 Li and coworkers surveyed the literature available on methods for the asymmetric construction of cyclic molecules, involving both organocatalysis and metal‐catalyzed processes, but concentrated exclusively on those containing a halogenated tetrasubstituted stereocenter, [34a] while China, Dohi and coworkers surveyed in the same year cyclization reactions, asymmetric or not, induced by a halogen [34b] . A few enantioselective halolactonizations were described, besides some racemic cascade processes.…”