Visible-Light-Promoted Decarboxylative Alkylation/Cyclization of Vinylcycloalkanes

An efficient strategy for visible-light-promoted decarboxylative alkylation of vinylcyclopropanes with alkyl N-(acyloxy)phthalimide esters through the dual C-C bond and single N-O bond cleavage, employing triphenylphosphine and lithium iodide as the photoredox system to synthesize 2-alkylated 3,4-dihydronaphthalenes, has been established. This alkylation/cyclization involves a radical process and undergoes a sequence of N-(acyloxy)phthalimide ester single-electron reduction, N-O bond cleavage, decarboxylative, alkyl radical addition, C-C bond cleavage, and intramolecular cyclization. Moreover, using the photocatalyst Na₂-Eosin Y instead of triphenylphosphine and lithium iodide, the vinyl transfer products are acquired when vinylcyclobutanes or vinylcyclopentanes are utilized as alkyl radical receptors.

Lighting Up the Organochalcogen Synthesis: A Concise Update of Recent Photocatalyzed Approaches

This review describes the recent advances in photocatalyzed reactions to form new carbon–sulfur and carbon–selenium bonds. With a total of 136 references, of which 81 articles are presented, the authors introduce in five sections an updated picture of the state of the art in the light-promoted synthesis of organochalcogen compounds (from 2019 to present). The light-promoted synthesis of sulfides by direct sulfenylation of C–C π-bonds; synthesis of sulfones; the activation of Csp2–N bond in the formation of Csp2–S bonds; synthesis of thiol ester, thioether and thioacetal; and the synthesis of organoselenium compounds are discussed, with detailed reaction conditions and selected examples for each protocol.

Visible-Light-Mediated Three-Component Cascade Sulfonylative Annulation

Visible-light-promoted cascade radical cyclization for the synthesis of sulfonylated benzimidazo/indolo[2,1-a]iso-quinolin-6(5H)-ones has been reported. The reaction provides transition-metal-free and expeditious access to sulfonylated polyaromatics. The use of sodium metabisulfite as a SO₂ surrogate and the rapid generation of molecular complexity using a three-component photochemical protocol are the salient features of this reaction manifold.

Visible-Light-Induced Decarboxylative Alkylation/Ring Opening and Esterification of Vinylcyclopropanes

A visible-light-induced four-component reaction of vinylcyclopropanes, N-(acyloxy)phthalimide esters, N,N-dimethylformamide (DMF), and H₂O through an oxidative ring opening of cyclopropane is presented. This procedure provides a new and effective way to construct formate esters. DMF is employed as both a solvent and the source of CHO. This difunctionalization of vinylcyclopropanes shows good functional group tolerance under room temperature. A radical pathway is involved, and carbonyl oxygen of ester originated from water in this transformation.

Alkylation/Ipso-cyclization of Active Alkynes Leading to 3-Alkylated Aza- and Oxa-spiro[4,5]-trienones

A method for the preparation of 3-alkylated spiro[4.5]trienones via alkylation/ipso-cyclization of activated alkynes with 4-alkyl-DHPs under transition-metal-free conditions is proposed. This alkylation successively undergoes the generation of alkyl radicals, addition of alkyl radicals to the alkynes, and intramolecular ipso-cyclization. The mechanism studies suggest that the alkylation/ipso-cyclization involves a radical process. This ipso-cyclization procedure shows a series of advantages, such as accessibility, mild conditions, high efficiency, greater safety, and an environmentally friendly method.

Visible-Light-Induced Dual Acylation of Alkenes for the Construction of 3-Substituted Chroman-4-ones

Heterocyclic compounds, especially oxygen-containing heterocyclic compounds, are crucial moieties in bioactive compounds and drug leads. Substituted chroman-4-ones are a kind of the most significant structural skeletons. Herein, we report a visible-light-induced dual acylation of alkenes for constructing 3-substituted chroman-4-ones, which undergoes a radical tandem cyclization reaction through carbon-carbon bond cleavage of oxime esters by a nitrogen-centered radical strategy. A series of 3-substituted chroman-4-ones were prepared with up to 86% yield.

The visible-light-induced acylation/cyclization of alkynoates with acyl oximes for the construction of 3-acylcoumarins

A nitrogen-centered radical-mediated carbon-carbon bond cleavage strategy is described to synthesize functionalized 3-acylcoumarins. The strategy is enabled by the visible-light-induced acylation/cyclization of alkynoates with various acyl oxime compounds in acetonitrile. The difunctionalization of carbon-carbon triple bonds precedes the generation of iminyl radicals, which is followed by the formation of acyl radicals. The acyl radicals then attack the carbon-carbon triple bonds, followed by 5-exo-trig cyclization and 1,2-ester migration. This strategy has wide substrate adaptability and good substituent tolerance.

In Situ Prepared Solar Light-Driven Flexible Actuated Carbon Cloth-Based Nanorod Photocatalyst for Selective Radical-Radical Coupling to Vinyl Sulfides

A global challenge faced by light harvesting photocatalyst is how to promote the selective organic transformation, such as C-S bond formation via radical-radical coupling under solar light. Here, we report a two-dimensional covalent organic frameworks (2D-COFs), poly (perylene-imide-benzoquinone) nanorod through in situ condensation on flexible activated carbon cloth (PPIBNR-FACC) to function as a light harvester material for highly selective radical-radical coupling to vinyl sulfides (i.e. C-S bond activation). Such a structure supports charge transfer from PPIBNR to FACC, which is essential for the selective radical-radical coupling. Hence, organic transformation is attaining high yields and selectivity (~99%) under solar light using in situ prepared PPIBNR-FACC photocatalyst. The structural virtues of PPIBNR-FACC will trigger the utmost investigations into designable and versatile 2D-COFs for fine chemical synthesis.

Visible-light-mediated cascade cyanoalkylsulfonylation/cyclization of alkynoates leading to coumarins via SO2 insertion

A visible-light-mediated cascade cyanoalkylsulfonylation/cyclization of alkynoates with cycloketone oxime compounds for the preparation of 3-cyanoalkylsulfonylcoumarins via SO₂ insertion is reported.

Copper-promoted cyanoalkylation/ring-expansion of vinylcyclopropanes with α-C-H bonds in alkylnitriles toward 3,4-dihydronaphthalenes

A copper-promoted oxidative cyanomethylation/ring-expansion of vinylcyclopropanes with α-C(sp3)-H bonds in alkyl nitriles is established for the generation of 1-cyanoethylated 3,4-dihydronaphthalenes. This cyanomethylation/ring-expansion involves a radical pathway and proceeds via cyanomethyl radical formation, radical addition and ring-expansion. This ring-expansion strategy offers a highly atom-economical route for the construction of nitrile-containing 3,4-dihydronaphthalenes, which can be transformed into other useful products under simple conditions.

Silver-promoted oxidative sulfonylation and ring-expansion of vinylcyclopropanes with sodium sulfinates leading to dihydronaphthalene derivatives

Silver-promoted sulfonylation and ring-expansion of vinylcyclopropanes with sodium sulfinates is established for the construction of 1-sulfonylmethylated 3,4-dihydronaphthalenes. This sulfonylation process involves a radical pathway, including sulfonyl radical formation, radical addition, ring-opening and cyclization. The 1-sulfonylmethylated 3,4-dihydronaphthalenes can be converted into other useful products.

Visible-light photoredox-catalyzed dual C–C bond cleavage: synthesis of 2-cyanoalkylsulfonylated 3,4-dihydronaphthalenes through the insertion of sulfur dioxide

A novel visible-light photoredox-catalyzed dual C–C bond cleavage of methylenecyclopropanes and cycloketone oximes for accessing 2-cyanoalkylsulfonated 3,4-dihydronaphthalenes is established.

Visible-light-induced cascade sulfonylation/cyclization of N-propargylindoles with aryldiazonium tetrafluoroborates via the insertion of sulfur dioxide

A simple and efficient visible-light-catalyzed cascade sulfonylation/cyclization of N-propargylindoles with K₂S₂O₅ and aryldiazonium tetrafluoroborates for the construction of 2-sulfonyl-substituted 9H-pyrrolo[1,2-a]indoles is developed.