Recent Progresses in the Preparation of Chlorinated Molecules: Electrocatalysis and Photoredox Catalysis in the Spotlight

Abstract

Among halogenated molecules, those containing chlorine atoms are fundamental in many areas such as pharmaceuticals, polymers, agrochemicals and natural metabolites. Despite the fact that many reactions have been developed to install chlorine on organic molecules, most of them rely on toxic and hazardous chlorinating reagents as well as harsh conditions. In an attempt to move towards more sustainable approaches, photoredox catalysis and electrocatalysis have emerged as powerful alternatives to traditional methods. In this review, we collect the most recent and significant examples of visible-light- or current-mediated chlorination published in the last five years.

Synthesis of a Bench-Stable Manganese(III) Chloride Compound: Coordination Chemistry and Alkene Dichlorination

“…Now, nearly half a century later, our serendipitous rediscovery led us to the current study. The importance of 1 is found in the simple fact that it enables access to MnCl 3 , which itself is not thermally stable. , The lack of Mn­(III) starting materials (Chart ) is unfortunate since it is synthetically useful in a variety of applications including alkene dichlorination, and the Mn 3+ ion is biologically important …”

“…To summarize, these observations support a radical mechanism involving stepwise Cl-atom transfer(s) from 1 , as opposed to nucleophilic chloride or electrophilic chloronium transfer (SI). , …”

Photoinduced Chloroamination Cyclization Cascade with N-Chlorosuccinimide: From N-(Allenyl)sulfonylamides to 2-(1-Chlorovinyl)pyrrolidines

“…Similar substrates have already been subjected to haloamination with a brominating reagent (LiBr, NBS or 1-bromopyrrolidin-2-one) in combination with transition metal catalysis, − or with iodine alone . As demonstrated by the recent blooming of chlorination protocols exploiting photoredox catalysis, we envisioned that a light mediated process could have been an ideal approach to tackle this chloroamino cyclization. Therefore, we selected a tosyl protected allenylamine ( 1a ) as our model substrate.…”

Iron Photocatalysis Applied to Oxidative Amidation of Aldehydes with NaCl

“…All of these reagents are prepared from Cl 2 and lead to the formation of significant amounts of organic waste (Scheme 1). [7] Among chlorinated compounds, acyl chlorides are versatile and reactive molecules. They are used as synthetic intermediates for the preparation of many useful organic moieties as carboxylic anhydrides, esters, hydroxamic acids and amides.…”

“…All of these reagents are prepared from Cl 2 and lead to the formation of significant amounts of organic waste (Scheme 1). [7] …”