Copper-Catalyzed Aminosulfonylation of O-Homoallyl Benzimidates with Sodium Sulfinates to Access Sulfonylated 1,3-Oxazines

Visible-light-promoted cascade cyclization of N-arylacrylamides with bromomethyl sulfone: access to sulfonylmethylated phenanthridines

We present a visible-light-promoted radical cascade cyclization reaction via sulfonylmethylation, cyano insertion, and radical cyclization of unactivated alkenes bearing cyano groups. This strategy enables the rapid synthesis of sulfonylmethylated phenanthridines under mild conditions with broad substrate compatibility, operational simplicity, and mild reaction conditions. The developed approach provides a novel pathway for assembling complex polycyclic nitrogen-containing frameworks, addressing a critical synthetic challenge and expanding the toolbox of photochemical transformations in organic synthesis.

Aerobic Copper-Catalyzed Hydroxysulfonylation of Vinylarenes with Sodium Sulfinates

A novel and efficient method for the intermolecular hydroxysulfonylation of vinylarenes using sodium sulfinates has been achieved through aerobic copper catalysis. This transformation proceeded smoothly with green air as the terminal oxidant in the presence of Cu (I)/1,10-phenanthroline as an efficient catalytic system, leading to an array of β-hydroxysulfones in moderate to high yields. The significant advantages of this protocol are the mild reaction conditions, readily available starting materials, good functional-group compatibility, synthetic convenience, and practicability. Preliminary mechanistic investigation suggested that the catalytic process should undergo a cascade of radical events involving the initial generation of sulfonyl radical followed by sulfonyl radical addition across alkenes and subsequent cross-coupling with air.

Substituent-Dependent, Switchable Synthesis of Nonaromatic and Aromatic Heterocyclic Sulfones Using Visible Light

In this Letter, we described a visible-light-induced switchable synthesis of nonaromatic and aromatic sulfonyl heterocycles. The product selectivity between 2,5-dihydropyrrole and pyrrole can be tuned by altering the substituent on the N atom of 1,6-diyne. We highlight the intricacy and efficiency of this approach in constructing molecular frameworks under mild conditions with a high functional group tolerance. This study elucidates the mechanism underlying product selectivity, highlighting its potential as a compelling alternative to traditional synthetic techniques.

Sulfonyl Radical-Induced Regioselective Cyclization of Enamide-Olefin To Form Sulfonylated 6-7-Membered Cyclic Enamines

Remarkable progress has been made in the radical cascade cyclization of heteroaryl- or aryl-tethered alkenes to construct benzene-fused frameworks via the cracking of aryl C-H bonds. In contrast, the radical cascade cyclization of linear dienes through the cracking of vinyl C-H bonds to construct nonbenzene-fused ring frameworks with endocyclic double bonds has significantly lagged behind, and major advances have largely been restricted to the generation of 5-membered heterocycles, such as pyrrolinones. Herein, we report the silver-mediated regioselective sulfonylation-cyclization of linear dienes with sodium sulfinates to form sulfonylated 6- and 7-membered cyclic enamines.

Copper-Catalyzed Oxyfluorosulfonylation of β,γ-Unsaturated Oximes with Sulfur Dioxide and Selectfluor for Isoxazoline-Functionalized Aliphatic Sulfonyl Fluorides

In this report, we describe a copper-catalyzed cascade reaction involving oxygen radical-induced cyclization/SO2 insertion/fluorination of β,γ-unsaturated oximes with sulfur dioxide and Selectfluor under mild conditions for the synthesis of isoxazoline-functionalized aliphatic sulfonyl fluorides. The synthetic potential of these compounds has been evaluated through diverse SuFEx reactions.

Aerobic Copper-Catalyzed Oxysulfonylation of Vinylarenes with Sodium Sulfinates under Mild Conditions: A Modular Synthesis of β-Ketosulfones

An aerobic copper-catalyzed oxysulfonylation of vinylarenes with sodium sulfinates is described. This protocol features mild reaction conditions, convenient operation, and broad substrate scope with respect to vinylarenes and sodium sulfinates. Notably, the protocol demonstrates excellent tolerance of functional groups such as chloro, bromo, ester, cyano, and nitro groups. Mechanistic investigations indicated that the reaction should undergo radical cascades involving a sulfonyl radical generated from sodium sulfinate with air as the terminal oxidant, addition across alkene to deliver a benzylic radical, and subsequent cross-coupling with air.

Electrochemical Ring-Opening of Cyclopropylamides with Alcohols toward the Synthesis of 1,3-Oxazines

An electrochemical method is presented to construct 1,3-oxazines by the oxidative ring-opening of cyclopropylamides with alcohols. This method avoids the use of external oxidants and thus shows good functional group tolerance. The substrate scope covers primary, secondary, and tertiary alcohols as well as (hetero)aryl amide-substituted cyclopropanes.

Photocatalytic C-C Bond Cleavage and Fluorosulfonylation of Strained Cycloalkanols for Carbonyl-Containing Aliphatic Sulfonyl Fluorides

In this report, we present a photocatalytic ring-opening fluorosulfonylation of strained cycloalkanols with sulfur dioxide and NFSI under mild conditions for the synthesis of carbonyl-containing aliphatic sulfonyl fluorides. The synthetic potential of the carbonyl-containing aliphatic sulfonyl fluoride products has been examined by diverse transformations, including SuFEx reactions and Baeyer-Villiger oxidation reactions. Mechanistic studies demonstrate that the reaction operates through a radical C-C bond cleavage/SO2 insertion/fluorination cascade process.

Photoinduced Photocatalyst-Free Cascade Cyclization of Alkynes with Sodium Sulfinates for the Synthesis of Benzothiophenes and Thioflavones

The subject of this investigation is a new method for the construction of sulfonylated heterocycles which overcomes the limitations of classical approaches using a cheap feedstock sulfonylating agent, especially under photocatalyst- and metal-free conditions.

Photocatalytic 1,2-Iminosulfonylation and Remote 1,6-Iminosulfonylation of Olefins

A new class of iminosulfonylation reagents were developed and extensively used in the 1,2-iminosulfonylation of various olefins. Olefins containing bioactive molecules, such as indomethacin, gemfibrozil, clofibrate, and fenbufen, afforded the desired iminosulfonylation products in synthetically useful yields. Furthermore, the first remote 1,6-iminosulfonylation of alkenes was realized by using oxime ester bifunctionalization reagents. Overall, more than 40 structurally diverse β-imine sulfones were obtained in moderate to excellent yields.

Switchable Regioselective 7-endo or 6-exo Iodocyclization of O-Homoallyl Benzimidates

We present a facile switchable regioselective 7-endo or 6-exo iodocyclization of O-homoallyl benzimidates here, which affords various iodo-substituted 1,3-oxazines and tetrahydro-1,3-oxazepines in a controllable manner. The products can further undergo substitution reactions to afford a series of rich functionalized target heterocyclic molecules. The developed protocol has the advantages of mild conditions, simple operation, and excellent functional group compatibility.

Electrochemically Enabled Intramolecular Amino- and Oxysulfonylation of Alkenes with Sodium Sulfinates to Access Sulfonylated Saturated Heterocycles

A practical and efficient electrochemical intramolecular amino- or oxysulfonylation of internal alkenes equipped with pendant nitrogen or oxygen-centered nucleophiles with sodium sulfinate was developed. Under undivided electrolytic cell conditions, a variety of sulfonylated N-heterocycles and O-heterocycles, such as tetrahydrofurans, tetrahydropyrans, oxepanes, tetrahydropyrroles, piperidines, δ-valerolactones, etc., were efficiently prepared from easily accessible unsaturated alcohols, carboxylic acids, and N-tosyl amines without the need for additional metal or exogenous oxidant. The robust electrochemical transformation features excellent redox economy, high diastereoselectivity, and broad substrate specificity, which provide a general and practical access to sulfone-containing heterocycles and would facilitate the related synthetic and biological studies based on this electrosynthesis.

NIS-Promoted Selective Amino-Diazidation and Amino-Iodoazidation of O-Homoallyl Benzimidates: Synthesis of Vicinal Diazido 1,3-Oxazines and Vicinal Iodoazido 1,3-Oxazines

Amines, especially those with multi-nitrogen moieties, are widespread in natural products and biologically active compounds. Thus, the development of direct and efficient methods to introduce multiple nitrogen-containing fragments into compounds in one step is highly desirable yet challenging. Herein, we report an NIS-promoted selective amino-diazidation and amino-iodoazidation of O-homoallyl benzimidates with NaN₃. By using this protocol, a variety of vicinal diazido-substituted 1,3-oxazines and vicinal iodoazido-substituted 1,3-oxazines were directly synthesized in a controllable manner. Preliminary mechanistic investigations revealed that the reaction operates through a NIS-promoted four-step cascade process. The developed method has the merits of metal-free, excellent functional group compatibility, simple operation, and mild conditions.

Palladium-Catalyzed Oxidant Dependent Switchable Aza-Wacker Cyclization and Oxidative Dimerization of Benzimidates

An oxidant dependent switchable palladium-catalyzed synthesis of 1,3-oxazines and benzohydrazonates (azines) from O-homoallyl benzimidates has been developed. The reaction involved aza-Wacker-type intramolecular cyclization of O-homoallyl benzimidates with Cu(OAc)2 as oxidant under Pd-catalysis to deliver 4-methylene-1,3-oxazines, whereas dimerization of O-homoallyl benzimidates with K2S2O8 as oxidant resulted remarkably in benzohydrazonates (azines). The reaction is atom economic with an easily operational procedure for divergent synthesis of important scaffolds.

Copper-Catalyzed Enantioselective Oxysulfenylation of Alkenols: Synthesis of Arylthiomethyl-Substituted Cyclic Ethers

Saturated heterocycles containing oxygen and sulfur are found in biologically significant molecules. The enantioselective oxysulfenylation of alkenols provides a straightforward synthesis route. To date, organocatalytic methods have dominated this approach. Herein, a complementary approach via copper catalysis is presented. This exoselective method provides enantioenriched arylthiomethyl-substituted tetrahydrofurans, phthalans, isochromans, and morpholines from acyclic alkenols. This method provides the largest scope to date for the exocyclization mode, and with generally high enantioselectivity. The enantioselectivity of this copper-catalyzed oxysulfenylation is rationalized by a proposed mechanism involving alkene oxycupration followed by C─S bond formation via radical-mediated atom transfer.

Visible-Light-Mediated Three-Component Radical Iodosulfonylative Cyclization of Enynes

An efficient three-component radical iodosulfonylative cyclization of enynes is described. The visible-light irradiation of iodoform with sulfinates enables sulfonyl radical generation under catalyst- and oxidant-free conditions and triggers the radical addition, cyclization and iodination cascade reactions, giving various vinyl iodide containing sulfones in moderate to good yields.

Complementary Copper-Catalyzed and Electrochemical Aminosulfonylation of O-Homoallyl Benzimidates and N-Alkenyl Amidines with Sodium Sulfinates

A complementary copper-catalyzed and electrochemical aminosulfonylation of O-homoallyl benzimidates and N-alkenyl amidines with sodium sulfinates was developed. The terminal alkene substrate produced sulfone-containing 1,3-oxazines and tetrahydropyrimidines in the presence of Cu(OAc)₂, Ag₂CO₃, and DPP, and under similar reaction conditions, sulfonylated tetrahydro-1,3-oxazepines were prepared from 1-aryl-substituted O-homoallyl benzimidates in moderate to good yields. For certain electron-rich 1,1-diaryl-substituted alkene substrates, the corresponding tetrahydro-1,3-oxazepines could also be obtained in similar or even higher yields via a green electrochemical technique.

Copper-assisted preparation of pyridinyl sulfonate esters from hydroxypyridines and sodium sulfinates

An efficient and powerful copper-assisted method for the effective conversion of a broad range of hydroxypyridines and sodium sulfinates into their corresponding pyridinyl tosylates was developed. Key features of this base- and ligand-free protocol include using the cheap and readily available CuBr2 as a medium and the use of sodium sulfinates as formal sulfonylation reagents. A variety of functional pyridinyl tosylates could be formed with good yields, which can easily be converted into C-C and C-N bond-containing compounds.

A new method for C(sp2)-H sulfonylmethylation with glyoxylic acid and sodium sulfinates

We herein describe a C4 sulfonylmethylation of pyrazol-5-amines with glyoxylic acid and sodium sulfinates. The reaction only needed to add water as the solvent, and it featured mild reaction condition,...