Regio- and Stereoselective Hydrosulfonylation of Electron-Deficient Alkynes: Access to Both E- and Z-β-Sulfonyl-α,β-Unsaturated Carbonyl Compounds

Acid-Promoted Phosphorylation of Ynones for the Synthesis of Phosphoryl Enones

An efficient phospha-aldol/Meyer-Schuster rearrangement cascade reaction between propargylic aldehydes and phosphine oxides has been developed in which various phosphoryl enones were obtained in moderate to excellent yields. A comprehensive series of mechanistic experiments, including the identification of key intermediates and the application of 18O isotope labeling, has confirmed that this cascade reaction proceeds through a phospha-aldol followed by Meyer-Schuster rearrangement cascade reaction.

Catalyst-Free Visible Light-Driven Hydrosulfonylation of Alkenes and Alkynes with Sulfonyl Chlorides in Water

A convenient and sustainable method for synthesizing sulfonyl-containing compounds through a catalyst-free aqueous-phase hydrosulfonylation of alkenes and alkynes with sulfonyl chlorides under visible light irradiation is presented. Unactivated alkenes, electron-deficient alkenes, alkyl and aryl alkynes can be hydrosulfonylated with various sulfonyl chlorides at room temperature with excellent yields and geometric selectivities by using tris(trimethylsilyl)silane as a hydrogen atom donor and silyl radical precursor to activate sulfonyl chlorides. Mechanistic studies revealed that the photolysis of tris(trimethylsilyl)silane in aqueous solution to produce silyl radical is crucial for the success of this reaction.

Novel Stereo-Induction Pattern in Pudovik Addition/Phospha-Brook Rearrangement Towards Chiral Trisubstituted Allenes

Despite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al., there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide-mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha-Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central-to-axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo-induction pattern in the Pudovik addition/phospha-Brook rearrangement cascade reaction.

Chemodivergent Sulfonylation of Enynones via Ionic and Radical Addition Modes of Sulfinic Acids

Different addition modes of sulfinic acids were developed for the chemodivergent sulfonylation of enynones, where the ionic sulfonylation to an alkyne moiety of enynones was effected through a salt-controlled syn-addition pathway. The radical sulfonylation of an alkene moiety also provided the stereodefined sulfonylated alkenes. A one-pot tandem sequence of the Ti(Oi-Pr)₄-catalyzed α-vinyl aldol condensation of (E)-β-chlorovinyl ketones followed by the chemodivergent sulfonylations was also explored, allowing for ready access to highly substituted dienes and enynes.

Metal-free hydrosulfonylation of α,β-unsaturated ketones: synthesis and application of γ-keto sulfones

γ-Keto sulfones are versatile building blocks and valuable intermediates in organic synthesis and pharmaceutical chemistry. Motivated by their excellent properties, we herein report a green, convenient, metal-free hydrosulfonylation method for a variety of ynones, vinyl ketones, and sodium sulfinates in the absence of stoichiometric oxidants. This operationally simple protocol provides straightforward and practical access to a wide range of γ-keto sulfones with broad functional group tolerance from easily available starting materials. Moreover, the β,γ-unsaturated keto sulfones could further react with 2,3-butadienoate to generate cyclopentenes in phosphine-mediated [3 + 2] cycloaddition.

Synthesis of Ynones via N-Iodosuccinimide-Mediated Oxidation of Propargyl Alcohols under Mild Conditions

A convenient and mild approach for the construction of ynones via N-iodosuccinimide (NIS)-mediated oxidation of propargyl alcohols has been described. This reaction could furnish the ynone products with a diversity of functional groups in moderate to excellent yields, and the flexibility of this method was demonstrated by the gram-scale experiment and further transformation.

Copper-Catalyzed Regio- and Stereoselective Sulfonylation of Alkynyl Imines with Sulfonyl Hydrazides: Access to (E)-β-Sulfonyl Enones

A copper-catalyzed sulfonylation of alkynyl imines with sulfonyl hydrazides has been developed, which exhibited excellent regio- and stereoselectivity and furnished a series of (E)-β-sulfonyl enones in moderate to good yields. Mechanistic studies suggest that this strategy goes through a radical process.

Atom-Economical, Catalyst-Free Hydrosulfonation of Densely Functionalized Alkenes: Access to Oxindole Containing Sulfones

An atom-economical hydrosulfonation of densely functionalized alkenes under catalyst-free conditions is described. Alkenes possessing hydroxy-oxindole moiety underwent hydrosulfonation on treatment with arylsulfinic acids in green media to afford the resulting...

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,...

Chalcone-inspired rA1 /A2A adenosine receptor ligands: Ring closure as an alternative to a reactive substructure

Over the past few years, great progress has been made in the development of high-affinity adenosine A₁ and/or A_2A receptor antagonists-promising agents for the potential treatment of Parkinson's disease. Unfortunately, many of these compounds raise structure-related concerns. The present study investigated the effect of ring closures on the rA₁ /A_2A affinity of compounds containing a highly reactive α,β-unsaturated carbonyl system, hence providing insight into the potential of heterocycles to address these concerns. A total of 12 heterocyclic compounds were synthesised and evaluated in silico and in vitro. The test compounds performed well upon qualitative assessment of drug-likeness and were generally found to be free from potentially problematic fragments. Most also showed low/weak cytotoxicity. Results from radioligand binding experiments confirm that heterocycles (particularly 2-substituted 3-cyanopyridines) can replace the promiscuous α,β-unsaturated ketone functional group without compromising A₁ /A_2A affinity. Structure-activity relationships highlighted the importance of hydrogen bonds in binding to the receptors of interest. Compounds 3c (rA₁ K_i  = 16 nM; rA_2A K_i  = 65 nM) and 8a (rA₁ K_i  = 102 nM; rA_2A K_i  = 37 nM), which both act as A₁ antagonists, showed significant dual A₁ /A_2A affinity and may, therefore, inspire further investigation into heterocycles as potentially safe and potent adenosine receptor antagonists.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Highly Chemo- and Enantioselective Rh-Catalyzed Hydrogenation of β-Sulfonyl-α,β-unsaturated Ketones: Access to Chiral γ-Ketosulfones

Rh-catalyzed highly chemo- and enantioselective hydrogenation of β-sulfonyl-α,β-unsaturated ketones was first successfully developed. Remarkably, a variety of enantioenriched γ-ketosulfones were generated in good to high yields with excellent chemo/enantioselectivities (82-99% yields, >99:1 chemoselectivity, 88 to >99% ee). Moreover, the gram-scale asymmetric hydrogenation was carried out smoothly in 97% yield and 97% ee. Preliminary DFT computations furnished a reasonable explanation for the high chemoselectivity and enantioselectivity.

Visible-light-induced anti-Markovnikov hydrosulfonation of styrene derivatives

A visible-light-induced anti-Morkovnikov hydrosulfonation reaction of styrene derivatives with sodium sulfinates has been developed, featuring mild reaction conditions, good functional-group tolerance, good yields and high regioselectivity.