Light-Induced Activation of C-X Bond via Carbonate-Assisted Anion-π Interactions: Applications to C-P and C-B Bond Formation

Generation and Application of Aryl Radicals Under Photoinduced Conditions

Photoinduced aryl radical generation is a powerful strategy in organic synthesis that facilitates the formation of diverse carbon-carbon and carbon-heteroatom bonds. The synthetic applications of photoinduced aryl radical formation in the synthesis of complex organic compounds, including natural products, physiologically significant molecules, and functional materials, have received immense attention. An overview of current developments in photoinduced aryl radical production methods and their uses in organic synthesis is given in this article. A generalized idea of how to choose the reagents and approach for the generation of aryl radicals is described, along with photoinduced techniques and associated mechanistic insights. Overall, this article offers a critical assessment of the mechanistic results as well as the selection of reaction parameters for specific reagents in the context of radical cascades, cross-coupling reactions, aryl radical functionalization, and selective C-H functionalization of aryl substrates.

Cobalt- or rhodium-catalyzed synthesis of 1,2-dihydrophosphete oxides via C-H activation and formal phosphoryl migration

A highly stereo- and chemoselective intermolecular coupling of diverse heterocycles with dialkynylphosphine oxides has been realized via cobalt/rhodium-catalyzed C-H bond activation. This protocol provides an efficient synthetic entry to functionalized 1,2-dihydrophosphete oxides in excellent yields via the merger of C-H bond activation and formal 1,2-migration of the phosphoryl group. Compared with traditional methods of synthesis of 1,2-dihydrophosphetes that predominantly relied on stoichiometric metal reagents, this catalytic system features high efficiency, a relatively short reaction time, atom-economy, and operational simplicity. Photophysical properties of selected 1,2-dihydrophosphete oxides are also disclosed.

Photocatalyst-free visible-light-promoted C(sp2)-P coupling: efficient synthesis of aryl phosphonates

A novel and efficient method for the synthesis of aryl phosphonates from aryl halides and trialkylphosphites via EDA complex-based photochemistry has been developed. It is demonstrated that aryl radicals, generated from the photoexcitation of the EDA complex formed by aryl halide and potassium thioacetate, could be intercepted with trialkylphosphite to produce the corresponding aryl phosphonates in moderate to good yields. It should be noted that the reaction is performed at room temperature in the absence of any transition metal catalyst, oxidant and photocatalyst, exhibiting high efficiency, high selectivity, and operational simplicity.

Catalytic π-π Interactions Triggered Photoinduced Synthesis of Biaryls

A highly regioselective photocatalytic method to access a variety of biaryl motifs under metal-free conditions has been developed. The organophotocatalyst is involved in π-π stacking interactions with the alkyne species, which promotes this photocatalytic process with thiophene. Mechanistic studies have shed light on these interactions and the overall process. Along with a broad functional-group tolerance and excellent regioselectivity, this protocol has been utilized in the late-stage functionalization of pharmaceuticals and other natural products.

Unified Approach to Diverse Heterocyclic Synthesis: Organo-Photocatalyzed Carboacylation of Alkenes and Alkynes from Feedstock Aldehydes and Alcohols

We report an organo-photocatalyzed carboacylation reaction that offers a springboard to create chemical complexity in a diversity-driven approach. The modular one-pot method uses feedstock aldehydes and alcohols as acyl surrogates and commercially available Eosin Y as the photoredox catalyst, making it simple and affordable to introduce structural diversity. Several biologically relevant skeletons have been easily synthesized under mild conditions in the presence of visible light irradiation by fostering a radical acylation/cyclization cascade. The proposed reaction mechanism was further illuminated by a number of spectroscopic studies. Furthermore, we applied this protocol for the late-stage functionalization of pharmaceuticals and blockbuster drugs.

Site-selective and metal-free C-H phosphonation of arenes via photoactivation of thianthrenium salts

Aryl phosphonates are prevalent moieties in medicinal chemistry and agrochemicals. Their chemical synthesis normally relies on the use of precious metals, harsh conditions or aryl halides as substrates. Herein, we describe a sustainable light-promoted and site-selective C-H phosphonation of arenes via thianthrenation and the formation of an electron donor-acceptor complex (EDA) as key steps. The method tolerates a wide range of functional groups including biomolecules. The use of sunlight also promotes this transformation and our mechanistic investigations support a radical chain mechanism.