Electrochemical generation and utilization of alkoxy radicals

Abstract

This highlight summarises electrochemical approaches for the generation and utilization of alkoxy radicals, predominantly focusing on recent advances (2012–present).

Electrochemical dehydroxymethylative functionalization of alkanols for forging C(sp3)–heteroatom bonds

“…Enabled by noble transition metal catalysis, a tandem reaction process of alcohol dehydrogenation followed by aldehyde decarbonylation was successfully employed (Scheme 1b(i)). 12 Moreover, the emergence of visible light photocatalysis has witnessed progress in the alkoxy radical-mediated cleavage of inert C–C bonds, 13 with the extrusion of formaldehyde to give carbon-centered radical intermediates. The following radical trapping process offers numerous opportunities to construct a wide variety of C(sp 3 )–C bonds with ease (Scheme 1b(ii)).…”

Tethering Three Radical Cascades for Controlled Termination of Radical Alkyne peri-Annulations: Making Phenalenyl Ketones without Oxidants

“…Due to the relatively high thermodynamic stability of the carbonyl moiety, radical fragmentation with the formation of a carbonyl group is a useful synthetic transformation (Figure a). Such transformations can proceed via fragmentations of either a C–O bond or a C–C bond and have found two notable applications: (a) to generate radical species − or (b) to make ketones. − In the first of these applications, the carbonyl group is the byproduct while, in the second type of applications, it is the target.…”

Alkoxy Radical Generation Mediated by Sulfoxide Cation Radicals for Alcohol-Directed Aliphatic C–H Functionalization

“…Given the innate reactivity of alkoxy radicals, their use as transient abstracting groups for C–H functionalization has been the subject of ongoing research. , The thermodynamics of the alkoxy radical can dictate a direct C–H abstraction of an aliphatic C–H bond given the bond dissociation energies (BDEs) exhibited by such moieties (BDE O–H ∼ 105 kcal/mol vs C–H alkyl ∼ 96–98 kcal/mol) . Furthermore, the inherent stabilization of the alkoxy radical via a β-scission manifold can be induced as a result of the strong carbonyl bond formed, typically cleaving a C–C bond and leaving a carbon-centered radical in the process . Finally, alkoxy radicals can undergo cyclization on pendant π-systems to furnish ether-type products .…”