Merging shuttle reactions and paired electrolysis for reversible vicinal dihalogenations

Abstract

Vicinal dibromides and dichlorides are important commodity chemicals and indispensable synthetic intermediates in modern chemistry that are traditionally synthesized using hazardous elemental chlorine and bromine. Meanwhile, the environmental persistence of halogenated pollutants necessitates improved approaches to accelerate their remediation. Here, we introduce an electrochemically assisted shuttle (e-shuttle) paradigm for the facile and scalable interconversion of alkenes and vicinal dihalides, a class of reactions that can be used both to synthesize useful dihalogenated molecules from simple alkenes and to recycle waste material through retro-dihalogenation. The reaction is demonstrated using 1,2-dibromoethane, as well as 1,1,1,2-tetrachloroethane or 1,2-dichloroethane, to dibrominate or dichlorinate, respectively, a wide range of alkenes in a simple setup with inexpensive graphite electrodes. Conversely, the hexachlorinated persistent pollutant lindane could be fully dechlorinated to benzene in soil samples using simple alkene acceptors.

Cathodic Corrosion of Metal Electrodes—How to Prevent It in Electroorganic Synthesis

“… 238 − 246 After that, only a few examples of electrosyntheses have been published, wherein both electrodes are required for the same process. 1 , 247 , 248 Hartmer and Waldvogel developed a domino oxidation–reduction sequence for the conversion of aldoximes to nitriles, where the first redox process is carried out on graphite anode and lead cathode is used in the second to generate the final compounds ( Scheme 18 ). 248 In this case, they utilized MTES, which is known from previous reports to protect the lead cathode from corrosion.…”

Arene C–H Iodination Using Aryl Iodides

“…= 90.5/9.5, 6b mono ) could be achieved with 5-bromopyridin-2-ol ligand. The absolute configuration of 6a mono after removal of the directing group was determined by x-ray crystallography (7). However, higher diastereoselectivity could not be obtained at present even after extensive study and further investigation is required.…”

Taming Electron Transfers: From Breaking Bonds to Creating Molecules

“…This approach is thus not directly transposable to catalytically shuttle two functional groups at once. Importantly, together with the Waldvogel group, Morandi and co‐workers showed that dissociative electron transfer pathways can be used to overcome bottlenecks in conventional shuttle catalysis schemes [25] . In constant current electrolysis conditions, 1,2‐dichloro species were reductively cleaved to mono‐chlorinated radicals, that readily expel chloride after further reduction.…”

“… Development of an e‐shuttle catalytic scheme (two functional groups shuttling) to overcome limitations of current (hydro)functionalization shuttle catalysis [25] …”