Vicinal diamines are a common structural motif in bioactive natural products, therapeutic agents, and molecular catalysts, motivating the continuing development of efficient, selective, and sustainable technologies for their preparation. We report an operationally simple and environmentally friendly protocol that converts alkenes and sodium azide-both readily available feedstocks-to 1,2-diazides. Powered by electricity and catalyzed by Earth-abundant manganese, this transformation proceeds under mild conditions and exhibits exceptional substrate generality and functional group compatibility. Using standard protocols, the resultant 1,2-diazides can be smoothly reduced to vicinal diamines in a single step, with high chemoselectivity. Mechanistic studies are consistent with metal-mediated azidyl radical transfer as the predominant pathway, enabling dual carbon-nitrogen bond formation.
Given its many distinct characteristics, electrochemistry represents an attractive approach to meet the prevailing trends in organic synthesis. In particular, electrocatalysisa process that integrates electrochemistry and small-molecule catalysishas the potential to substantially improve the scope of synthetic electrochemistry and provide a wide range of useful transformations. Recently, we have demonstrated new catalytic approaches that combine electrochemistry and redox-metal catalysis for the oxidative difunctionalization of alkenes to access a diverse array of vicinally functionalized structures. This Perspective details our design principles underpinning the development of electrochemical diazidation, dichlorination, and halotrifluoromethylation of alkenes, which were built on foundational work by others in the areas of synthetic electrochemistry, radical chemistry, and transition-metal catalysis. The introduction of redox-active Mn catalysts allows the generation of radical intermediates from readily available reagents at low potentials under mild conditions. These transition metals also impart selectivity control over the alkene functionalization processes by functioning as radical group transfer agents. As such, our electrocatalytic difunctionalization reactions exhibit excellent chemoselectivity, broad substrate scope, and high functional group compatibility. Specifically, anodically coupled electrolysis, an approach that pairs two single-electron oxidation events in a parallel manner, enables the development of regio- and chemoselective heterodifunctionalization of alkenes. The products of the new transformations we describe in this Perspective represent pertinent structures in numerous medicinally relevant compounds. We anticipate that the design parameters presented here are general and will provide a platform for the development of electrocatalytic systems for other challenging organic redox transformations.
We report a Mn-catalyzed electrochemical dichlorination of alkenes with MgCl as the chlorine source. This method provides operationally simple, sustainable, and efficient access to a variety of vicinally dichlorinated compounds. In particular, alkenes with oxidatively labile functional groups, such as alcohols, aldehydes, sulfides, and amines, were transformed into the desired vicinal dichlorides with high chemoselectivity. Mechanistic data are consistent with metal-mediated Cl atom transfer as the predominant pathway enabling dual C-Cl bond formation and contradict an alternative pathway involving electrochemical evolution of chlorine gas followed by Cl-mediated electrophilic dichlorination.
We report a mild and efficient electrochemical protocol to access a variety of vicinally C–O and C–N difunctionalized compounds from simple alkenes. Detailed mechanistic studies revealed a distinct reaction pathway from those previously reported for TEMPO-mediated reactions. In this mechanism, electrochemically generated oxoammonium ion facilitates the formation of azidyl radical via a charge-transfer complex with azide, TEMPO–N3. DFT calculations together with spectroscopic characterization provided a tentative structural assignment of this charge-transfer complex. Kinetic and kinetic isotopic effect studies revealed that reversible dissociation of TEMPO–N3 into TEMPO• and azidyl precedes the addition of these radicals across the alkene in the rate-determining step. The resulting azidooxygenated product could then be easily manipulated for further synthetic elaborations. The discovery of this new reaction pathway mediated by the TEMPO+/TEMPO• redox couple may expand the scope of aminoxyl radical chemistry in synthetic contexts.
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.
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