Visible-Light-Catalyzed C–C Bond Difunctionalization of Methylenecyclopropanes with Sulfonyl Chlorides for the Synthesis of 3-Sulfonyl-1,2-dihydronaphthalenes

A General Platform for Visible Light Sulfonylation Reactions Enabled by Catalytic Triarylamine EDA Complexes

Catalytic electron donor-acceptor (EDA) complexes have recently emerged as a powerful and sustainable alternative to iridium- and ruthenium-based photoredox synthetic methods. Yet, these complexes remain underexplored and reliant on the use of meticulously designed acceptors that require previous installation. Herein, we report a novel EDA complex employing tris(4-methoxyphenyl) amine as a catalytic donor for the sulfonylation of alkenes using inexpensive and readily available sulfonyl chlorides. Applying this operationally simple, visible-light-mediated general platform, we report both the redox-neutral and net-reductive functionalization of more than 60 substrates, encompassing vinylic or allylic sulfonylation, hydrosulfonylation, and sulfamoylation of activated and unactivated alkenes and alkynes.

Visible-Light-Mediated Dual Functionalization of Allenes: Regio- and Stereoselective Synthesis of Vinylsulfone Azides

A gentle and effective method for the photocatalytic dual functionalization of allenes with high regio- and stereoselectivity using a nonmetallic catalyst is described. Inexpensive and easily available sulfinates and TMSN3 were employed as sulfone and azido sources, respectively. The method is characterized by satisfactory substrate compatibility and tolerance toward functional groups. The straightforward initial mechanistic experiments suggested that the reaction could follow a radical pathway. The synthesis of vinylsulfone azide derivatives presented here offers a promising scaffold for the future development of vinyl sulfone-based drugs and functional bioorthogonal reagents.

Visible-Light-Induced Intramolecular Tandem Cyclization of Unactivated Indoloalkynes for the Synthesis of Sulfonylated and Selenylated Indolo[1,2-a]quinolines

A convenient and efficient visible-light-induced method has been developed for the construction of sulfonated and selenylated indolo[1,2-a]quinolines through sulfonyl or selenyl radical-initiated tandem cyclization of unactivated alkynes with sodium sulfinates or diaryl diselenides under mild conditions. This protocol, which simply utilizes visible light as the safe and eco-friendly energy source and an inexpensive and nontoxic organic dye as a photocatalyst without the aid of an external photocatalyst, provides various sulfonyl- and selenyl-containing indolo[1,2-a]quinolines in moderate to good yields.

Photoredox-Catalyzed Synthesis of 3-Sulfonylated Pyrrolin-2-ones via a Regioselective Tandem Sulfonylation Cyclization of 1,5-Dienes

A mild, visible-light-induced, regioselective cascade sulfonylation-cyclization of 1,5-dienes with sulfonyl chlorides through the intermolecular radical addition/cyclization of alkenes C(sp²)-H was developed. This procedure proceeds well and affords a mild and efficient route to a range of monosulfonylated pyrrolin-2-ones at room temperatures.

Visible-light-induced reactions of methylenecyclopropanes (MCPs)

Diverse, visible-light-induced transformations of methylenecyclopropanes (MCPs) have been reported in recent years, attracting significant attention from synthetic chemists. As readily accessible strained molecules, MCPs have sufficient reactivity to selectively generate different target products, through reactions with various radical species upon visible-light irradiation under regulated reaction conditions. These transformations can be classified into three subcategories of reaction pathway, forming ring-opened products, cyclopropane derivatives, and alkynes. These products include pharmaceutical intermediates and polycyclic/heterocyclic compounds that are challenging to obtain using traditional methods. This review summarizes the recent advancements in this field.

Oxidative functionalization of alkylidenecyclopropanes and alkylidenecyclobutanes: a versatile platform to access nitrated cyclopropanes and cyclobutanes

A divergent radical nitration of alkylidenecyclopropanes (ACPs) and alkylidenecyclobutanes (ACBs) with Fe(NO₃)₃·9H₂O or AgNO₂ has been achieved, affording three categories of products including β-nitro alcohol, α-nitro ketone and nitro nitratosation products with yields up to 90%. Particularly, the cyclopropyl and cyclobutyl rings were conserved in the products. The applicability of this method was demonstrated by the scale-up experiment and reduction of the nitro into an amino group. Preliminary mechanistic studies suggested that the nitro radical was involved in the reaction process.

Visible-light-induced acylation/cyclization of active alkenes: facile access to acylated isoquinolinones

Nitrogen heterocycles, especially polycyclic compounds, are significant skeletons in valuable molecules. Herein, we developed an efficient and practical visible-light-induced acylation/cyclization of active alkenes with acyl oxime derivatives for constructing acylated indolo/benzimidazo-[2,1,a]isoquinolin-6(5H) ones. This reaction was compatible with various functional groups and a series of fused indole/imidazole skeletons were prepared in up to 95% yield at room temperature.

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.

Organic-photoredox-catalyzed three-component sulfonylative pyridylation of styrenes

An efficient, metal-free protocol for the three-component sulfonylative pyridylation of styrenes via organic-photoredox catalysis is described. This metal-free process enables the direct and selective installation of sulfonyl and heteroaryl motifs and tolerates a wide array of functional groups as well as complex molecular scaffolds, that could complement previous methods and would be of interest in pharmaceutical research.

An efficient, metal-free protocol for the three-component sulfonylative pyridylation of alkenes via organic-photoredox catalysis is described.

Visible-light-induced radical cascade cyclization of 1-(allyloxy)-2-(1-arylvinyl)benzenes with sulfonyl chlorides for the synthesis of sulfonated benzoxepines

A visible light photocatalyzed cascade sulfonylation/cyclization of 1-(allyloxy)-2-(1-arylvinyl)benzenes with sulfonyl chlorides for the construction of sulfonated benzoxepines is developed.

Intramolecular difunctionalization of methylenecyclopropanes tethered with carboxylic acid by visible-light photoredox catalysis

We have developed a visible-light photoredox catalyzed intramolecular difunctionalization of MCPs to access spiro[cyclopropane-1,2-indan]one from easily prepared methylenecyclopropanes tethered with carboxylic acid.

Construction of polysubstituted spiro[2.3] or [3.3] cyclic frameworks fused with a tosylated pyrrolidine promoted by visible-light-induced photosensitization

A novel visible-light-induced intramolecular [2 + 2] cycloaddition of methylenecyclopropanes (MCPs) for the rapid construction of polysubstituted spiro[2.3] or [3.3] cyclic frameworks fused with a tosylated pyrrolidine.

Sulfonyl radical-induced regioselective cyclization of 3-aza-1,5-enynes with sulfonyl chlorides to produce 1,2-dihydropyridines by copper catalysis

A Cu-catalyzed regioselective cyclization of 3-aza-1,5-enynes with sulfonyl chlorides for the synthesis of 1,2-dihydropyridines is described.

Recent Advances on Synthetic Methodology Merging C-H Functionalization and C-C Cleavage

The functionalization of C-H bonds has become a major thread of research in organic synthesis that can be assessed from different angles, for instance depending on the type of catalyst employed or the overall transformation that is carried out. This review compiles recent progress in synthetic methodology that merges the functionalization of C-H bonds along with the cleavage of C-C bonds, either in intra- or intermolecular fashion. The manuscript is organized in two main sections according to the type of substrate in which the cleavage of the C-C bond takes place, basically attending to the scission of strained or unstrained C-C bonds. Furthermore, the related research works have been grouped on the basis of the mechanistic aspects of the different transformations that are carried out, i.e.,: (a) classic transition metal catalysis where organometallic intermediates are involved; (b) processes occurring via radical intermediates generated through the use of radical initiators or photochemically; and (c) reactions that are catalyzed or mediated by suitable Lewis or Brønsted acid or bases, where molecular rearrangements take place. Thus, throughout the review a wide range of synthetic approaches show that the combination of C-H and C-C cleavage in single synthetic operations can serve as a platform to achieve complex molecular skeletons in a straightforward manner, among them interesting carbo- and heterocyclic scaffolds.

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.

Rapid construction of cyclopenta[b]naphthalene frameworks from propargylic alcohol tethered methylenecyclopropanes

We have developed a new synthetic methodology for the rapid construction of cyclopenta[b]naphthalene frameworks from the reaction of propargylic alcohol tethered methylenecyclopropanes with mesyl chloride in the presence of triethylamine through cascade cyclization. The reaction can be performed under mild conditions without the use of transition metals, affording the target products in moderate to good yields, and this cyclization reaction process can be scaled up to a gram-scale synthesis.

Electrochemical Synthesis of β-Ketosulfones from Switchable Starting Materials

A synthesis of β-ketosulfones via sulfination of aryl methyl ketones and aryl acetylenes with sodium sulfinates under mild electrochemical conditions, in moderate to good chemical yields, is described. In particular, an electrochemical sulfination reaction of alkynes with sulfinate salts has never been explored. An environmentally friendly characteristic of this reaction is that it uses electricity as a valuable energy source for electrochemical synthesis of β-ketosulfones. This strategy is more convenient and practical compared to previous approaches.

A highly efficient method for the construction of cyclopropane-containing dihydroindole derivatives from indolemethylenecyclopropanes with DIAD and DEAD

A highly efficient method for the construction of cyclopropane-containing dihydroindole derivatives from indolemethylenecyclopropanes with DIAD and DEAD has been disclosed. The transformation could occur under catalyst-free conditions at ambient temperature to afford dihyroindole derivatives in good yields. It has been proved that the strained moiety of methylenecyclopropane in the substrate of indolemethylenecyclopropane is critical and DFT calculations reveal that the reaction proceeds through a two-step pathway.

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.

Lewis or Brønsted acid-catalysed reaction of propargylic alcohol-tethered alkylidenecyclopropanes with indoles and pyrroles for the preparation of polycyclic compounds tethered with indole or pyrrole motif

We developed a facile synthetic method to access the cyclopenta[b]naphthalene skeleton from Lewis or Brønsted acid-catalysed propargylic alcohol-tethered alkylidenecyclopropanes with indole and pyrrole derivatives.

Copper/B2pin2-Catalyzed Difluoroalkylation of Methylenecyclopropanes with Bromodifluorinated Acetates and Acetamides: One-Pot Synthesis of CF2-Containing Dihydronaphthalene Derivatives

Novel copper/B₂pin₂-catalyzed difluoroalkylation of methylenecyclopropanes with bromodifluorinated acetates and acetamides via a tandem radical process involving ring-opening/intramolecular cyclization has been reported. This protocol is not only tolerated to a diverse range of substrates but also applicable to the synthesis of useful difluoromethylated compounds. Moreover, the reaction could be performed on a gram scale with a high yield, which opens up the possibility for practical applications.

Visible-light-promoted hydroxysulfonylation of alkylidenecyclopropanes: synthesis of cyclopropane-containing β-hydroxysulfones

Cyclopropane-containing β-hydroxysulfones and cyclopropyl styrenes have been synthesised from readily available ACPs and sulfuryl chloride via visible-light photoredox catalysis.

Visible-light-mediated difunctionalization of vinylcyclopropanes for the synthesis of 1-sulfonylmethyl-3,4-dihydronaphthalenes

An efficient method for the visible-light-mediated sulfonylation/arylation of the C–C σ-bond in vinylcyclopropanes with sulfonyl chlorides to synthesize 1-sulfonylmethyl-substituted 3,4-dihydronaphalenes has been developed.

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.

Visible-light promoted one-pot synthesis of sulfonated spiro[4,5]trienones from propiolamides, anilines and sulfur dioxide under transition metal-free conditions

A novel visible-light promoted sulfonylation/ipso-cyclization of N-arylpropiolamides with aromatic amines and DABCO·(SO₂)₂ to synthesize various sulfonated spiro[4,5]trienones is reported.