Iron‐Promoted Radical Reactions: Current Status and Perspectives

Abstract

Catalysis based on precious metals has reached an incredible level of sophistication and has found widespread use and application,b oth in academia andi ni ndustry.H owever,o wing to the environmental impact, cost, and low abundance, catalysis based on inexpensive, abundant,a nd environmentally benign first-row transition metals has become av aluable alternative to traditional reactions promoted by their less-abundantc ounterparts. From economic and ecological perspectives, iron salts and iron metal complexes are highly promising candidates to replace costly and toxic metals. In recent years, iron complexes have been used to promote the formation of radicals. Photoredox chemistry is av aluablem ethod for the generation of radical species under mild conditions, but it often relies on rare-earth-metal complexes.T he employment of iron complexes for the generation of radicals is attractive for the development of sustainable, simple, and effective procedures.I nt his Focus Review,w eh ighlight and summarize recent radicalr eactions promoted by iron complexes and their application in organic reactions.

Radical Cyclization of Alkene‐Tethered Ketones Initiated by Hydrogen‐Atom Transfer

“…With optimum reaction conditions in hand, we evaluated this iron‐triggered radical cyclization in related substrates, which were either of synthetic or mechanistic interest (Table ). The related compound 3 a , with an endocyclic double bond also gave 2 .…”

Diorganyl Dichalcogenides and Copper/Iron Salts: Versatile Cyclization System To Achieve Carbo- and Heterocycles from Alkynes

“…Iron-mediated protocols have been successfully employed for the synthesis of different organic substances through carbon-carbon and carbon-heteroatom bond formation. 10,29,32 Particularly, iron-promoted cyclization reactions of alkynyl substrates in the presence of diorganyl dichalcogenides consist of an important synthetic advancement concerning the preparation of functionalized hetero-and carbocyclic nucleus. Usually, the reaction pathway related to these protocols involves the interaction of the iron salt with the diorganyl dichalcogenide to generate electrophilic ironchalcogen species IX which coordinates with the carbon-carbon triple bond leading to the three-membered cyclic chalcogenonium cation X.…”

“…7,8 More specifically, iron and copper have been efficiently applied in cyclization reactions for the synthesis of a variety of cyclic substances. 9,10 Concomitantly, the chemistry of organochalcogen-containing carbo-and heterocycles has grown considerably, in particular, due to their biological and pharmacological properties 11,12 as well as their vast synthetic applications. 13,14 In this sense, organochalcogen-derived cyclic substances have received attention by the scientific community as potential pharmacological agents due to their wide range activities such as anticancer, antidepressant-like, and antioxidant.…”

Radical Transformations towards the Synthesis of Quinoline: A Review

“…[37] Although these methods provided unlimited access to compound libraries with several advantages, but most of them suffer from some limitations, such as acid or hazardous catalyst reactions, harsh reaction conditions, and tedious workup. [38] Thus, in the past few years, radical-mediated reactions blossomed and emerged as much efficient tool to construct heterocycles with several advantages over traditional methods, [39] mainly the radical cascade reactions focused on electrocatalysis, transition metal-mediated, [40] and photoredox catalysis using oxidants, [41] metal salts, [42] visible-light (Blue LED) photocatalysis [43] and so forth. [44] In addition, radical-mediated or cyclization reactions bloomed in the synthesis of a great number of heteroarenes along with Quinoline with multiple advantages, including mild reaction conditions, readily available starting substrates, high atom-and step-economy, which avoid time and cost consumption.…”