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The aerobic dehydrogenative lactonization of alkenoic acids facilitated by a cooperative nonmetallic catalyst pair is reported. The title procedure relies on the adjusted interplay of a photoredox and a selenium-π-acid catalyst, which allows for the regiocontrolled construction of five- and six-membered lactone rings in yields of up to 96%. Notable features of this method are pronounced efficiency and practicality, good functional group tolerance, and high sustainability, since ambient air and visible light are adequate for the clean conversion of alkenoic acids into their respective lactones. The title method has been used as a case study to elucidate the general mechanistic aspects of the dual selenium-π-acid/photoredox catalysis. On the basis of NMR spectroscopic, mass spectrometric, and computational investigations, a more detailed picture of the catalytic cycle is drawn and the potential role of trimeric selenonium cations as catalytically relevant species is discussed.

Herein, we present a detailed kinetic and thermodynamic analysis of the anodic allylic esterification of alkenes as well as the bulk application of the anodic amination and esterification of nonactivated alkenes catalyzed by diselenides. The electrochemical study led to a comprehensive picture of the coupled electrochemical and chemical reaction steps. Cyclic voltammetry measurements are consistent with a bimolecular step after initial electrochemical 1e − oxidation of the diphenyl diselenide catalyst, 1a, and therefore we postulate a dimerization of the cation, which reacts very rapidly with the alkene, forming the addition product, i.e. the selenolactone 2a. Subsequent electrochemical oxidation of 2a occurs at a slightly higher potential than initial oxidation of 1a. The second oxidation is also followed by a bimolecular process and we hypothesize a dimerization of the cation, which finally eliminates 1a and protons in the rate-determining step, forming the product. Electrochemical analysis of various catalysts, i.e. nonsterically demanding diaryl diselenides with electron withdrawing and donating substituents, revealed that the oxidation potential of the catalyst and the intermediate can be readily tuned by the substituents, thus, prospectively allowing for a wide application of olefinic and nucleophilic substrates. The substituent pattern at the alkene has a smaller influence on the redox potential of the adduct. Controlled potential electrolysis experiments employing different nucleophiles proved that the reaction can be run electrochemically. The functionalization of unactivated alkenes with N-and O-nucleophiles was successfully demonstrated in several bulk electrolysis experiments, and the products were isolated in good yields.

Catalytic oxidative functionalizations of simple, nonpolarized alkenes represent one of the lynchpin technologies in the realm of modern methodological chemical research. In this context, Lewis-acidic selenium species have experienced a steadily increasing scope of applications in catalytic oxidations of simple alkenes throughout recent years. In analogy to their metallic counterparts, such as cationic gold and platinum complexes, selenenium ions (i.e., RSe+) display an exceptional reactivity toward π-bonds, which allows for the highly chemoselective electrophilic functionalization of alkenes. This distinct reactivity profile enabled the development of a diverse array of catalytic bond-forming processes, such as allylic and vinylic aminations, inter- and intramolecular esterifications, halogenations, and etherifications. Remarkable features associated with such protocols are the high regiocontrol, the commonly mild reaction conditions, the operational simplicity by which selenium-catalyzed alkene oxidations can be conducted, and the exquisite functional group tolerance. These aspects make selenium-π-acid catalysis very attractive for late-stage oxidations of polyfunctionalized molecules, an asset that still remains to be fully explored. In this Perspective, the latest contributions to the field of selenium-π-acid catalysis are delineated and placed into context with indicatory insights gained from previous methodological, mechanistic, and theoretical studies.

A new selenium-catalyzed protocol for the direct, intramolecular amination of C(sp(2))-H bonds using N-fluorobenzenesulfonimide as the terminal oxidant is reported. This method enables the facile formation of a broad range of diversely functionalized indoles and azaindoles derived from easily accessible ortho-vinyl anilines and vinylated aminopyridines, respectively. The procedure exploits the pronounced carbophilicity of selenium electrophiles for the catalytic activation of alkenes and leads to the formation of C(sp(2))-N bonds in high yields and with excellent functional group tolerance.

A new metal-free catalysis protocol for the oxidative coupling of nonactivated alkenes with simple carboxylic acids has been established. This method is predicated on the cooperative interaction of a diselane and a photoredox catalyst, which allows for the use of ambient air or pure O2 as the terminal oxidant. Under the title conditions, a range of both functionalized and nonfunctionalized alkenes can be readily converted into the corresponding allylic ester products with good yields (up to 89%) and excellent regioselectivity as well as good functional group tolerance.

Oxidative Se-catalyzed C(sp3)-H bond acyloxylation has been used to construct a diverse array of isobenzofuranones from simple ortho-allyl benzoic acid derivatives. The synthetic procedure employs mild reaction conditions and gives high chemoselectivity enabled by an inexpensive organodiselane catalyst. The presented approach offers a new synthetic pathway toward the core structures of phthalide natural products.

Cooperativity has become a mainstay in the context of multicatalytic reaction design. The combination of two or more catalysts that possess mechanistically distinct activation principles within a single chemical setting can enable bond constructions that would be impossible for any of the catalysts alone. An emerging subdomain within the field of multicatalysis is characterized by single‐electron transfer processes that are sustained by the synergistic merger of sulfur or selenium organocatalysis with photoredox catalysis. From a synthetic viewpoint, such processes have tremendous value, as they can offer new and economic pathways for the concise assembly of complex molecular architectures. Thus, the aim of this Review is to highlight recent methodological progress made in this area and to contextualize representative transformations with the mechanistic underpinnings that enable these reactions.