Anodically Coupled Electrolysis for the Heterodifunctionalization of Alkenes

Abstract

The emergence of new catalytic strategies that cleverly adopt concepts and techniques frequently used in areas such as photochemistry and electrochemistry has yielded a myriad of new organic reactions that would be challenging to achieve using orthodox methods. Herein, we discuss the strategic use of anodically coupled electrolysis, an electrochemical process that combines two parallel oxidative events, as a complementary approach to existing methods for redox organic transformations. Specifically, we demonstrate anodically coupled electrolysis in the regio- and chemoselective chlorotrifluoromethylation of alkenes.

Synthesis of Chlorotrifluoromethylated Pyrrolidines by Electrocatalytic Radical Ene‐Yne Cyclization

“…Using an electrochemical approach, we recently developed a method for the chlorotrifluoromethylation of alkenes using commercially available Langlois reagent (CF 3 SO 2 Na) and MgCl 2 as functional group donors and Mn(OAc) 2 as a catalyst (Scheme A) . The proposed mechanism entails the parallel oxidative generation of two open‐shell intermediates, CF 3 .…”

“…This radical is highly unstable (bond dissociation energy of an alkenyl C−H bond is approximately 110 kcal mol −1 ) and can in principle participate in a variety of side reactions. In our previous studies, we demonstrated that an sp 3 carbon‐centered radical can be efficiently captured by [Mn III ]−Cl to form a C−Cl bond . We reasoned that this Mn‐bound latent Cl radical would also react with an alkenyl radical and that the efficiency and selectivity of this atom transfer process could be controlled by tuning the ligand on the metal center.…”

“…Although these side products have not been definitely identified, we hypothesize that competing direct difunctionalization of the alkene or alkyne groups in 20 and reactions involving the labile H atom α to the O in 21 complicated the desired transformation. Indeed, in our previously reported alkene chlorotrifluoromethylation reaction, hydrogen atom abstraction was often observed with substrates bearing labile C−H bonds as evident from the formation of CF 3 H. Attempts to adopt our method in the synthesis of azapane type structures from 1,8‐enynes (e.g., 21 ) proved unsuccessful. Although the cyclization product was detected with NMR and mass spectrometry, the slow kinetics of the ring‐closure process allowed various side reactions including direct alkene difunctionalization and aromatic trifluoromethylation to plague the desired reactivity.…”

Hexafluoro‐2‐Propanol‐Promoted Electro‐Oxidative [3+2] Annulation of 1,3‐Dicarbonyl Compounds and Alkenes

“…Electrosynthesis, which can avoid the external oxidants by employing the electrons to achieve the redox reaction, is considered as a versatile and eco‐friendly synthetic strategy and has experienced remarkable renaissance in recent years . The electrochemical alkene difunctionalization is emerging as a approach to construct C−C, C−N, C−O, C−Cl and so on . We envisioned acyclic 1,3‐dicarbonyl compounds, which has interested the chemists over the years due to the high oxidation potential of acyclic 1,3‐dicarbonyl compounds, might serve as C‐radical sources and nucleophilic oxygen sources to react with alkenes, achieving the electro‐oxidative [3+2] annulation with hydrogen evolution.…”

Der “Persistent Radical Effect” in der organischen Chemie

“…Die Autoren nutzten hierzu einen elektrochemischen Ansatz mit Mn III -Chlorid als Cl-Atom-Transfer-Reagenz. [144]…”