Atmospheric Oxygen Mediated Radical Hydrothiolation of Alkenes

Iodine-Promoted Reductive Sulfenylation Using Ketones as Hydride Donors

Herein, an iodine-promoted reductive sulfenylation reaction of ketones with disulfides has been developed. This method provides an approach for synthesizing unsymmetrical alkyl-alkyl and alkyl-aryl sulfides in a single step. Investigation of the reaction mechanism revealed that ketones play a dual role in this process. They react with disulfides to produce vinyl thioethers and act as effective organic hydride donors, reducing the number of vinyl thioethers that are formed in situ. This study expands the range of applications of ketones in chemical synthesis.

Catalyst/Metal/Solvent-Free Markovnikov Hydrothiolation of Unactivated Alkenes with Dithiocarbamic Acids

Catalyst-free Markovnikov-selective hydrothiolation of unactivated alkenes still remains a great challenge. Herein, we develop a catalyst/metal/solvent-free methodology for the Markovnikov hydrothiolation of unactivated alkenes with in situ prepared dithiocarbamic acids, providing a wide array of alkyl dithiocarbamates. A variety of terminal, internal, cyclic, and acyclic unactivated alkenes were applied successfully in this protocol. This three-component thiol-ene reaction can be considered as a new family of click reactions.

Radical Mediated Decarboxylation of Amino Acids via Photochemical Carbonyl Sulfide (COS) Elimination

Herein, we present the first examples of amino acid decarboxylation via photochemically activated carbonyl sulfide (COS) elimination of the corresponding thioacids. This method offers a mild approach for the decarboxylation of amino acids, furnishing N-alkyl amino derivatives. The methodology was compatible with amino acids displaying both polar and hydrophobic sidechains and was tolerant towards widely used amino acid-protecting groups. The compatibility of the reaction with continuous-flow conditions demonstrates the scalability of the process.

Traceless Thioacid-Mediated Radical Cyclization of 1,6-Dienes

Five-membered ring systems are ubiquitous throughout natural products and synthetic therapeutics, and thus, efficient methods to access this essential scaffold are required. Herein, we report the thioacid-mediated, 5-exo-trig cyclization of various 1,6-dienes, with high yields of up to 98%. The labile thioester functionality can be exploited to generate a free thiol residue which can be used as a functional handle or removed entirely to provide the traceless cyclized product.

Visible/solar-light-driven thiyl-radical-triggered synthesis of multi-substituted pyridines

A light-triggered synthesis of thio-functionalized pyridines is demonstrated using γ-ketodinitriles, thiols, and eosin Y as the photocatalyst. The reaction proceeds via the selective attack on one of the cyano groups by an in situ generated thiyl radical. The reaction also proceeds with nearly equal efficiency using direct sunlight. Large-scale synthesis and a few useful synthetic transformations of the substituted pyridines are also performed.

n-Butyllithium-Induced Tandem [3,3]-Sigmatropic Rearrangement and Carbonyl Olefination of Allyl-1,1-dichlorovinyl Ethers

Exposure of dichlorovinyl ethers 1 to n-butyllithium and addition of saturated or unsaturated aldehydes, ketones, or esters at ambient temperature furnishes rearranged α,β-unsaturated carboxylic acids, isolated as their corresponding methyl esters 2 in 48-91% overall yields. Exposure of dichlorovinyl ethers 1 to n-butyllithium, addition of aldehydes, ketones, dialdehydes, or diketones at -78 °C, and warming to 80 °C in the presence of SiO₂ provide 1,4-dienes 3 or cycloalken-1-ols (or their dehydration products) 4 in 45-72% overall yields.

Brønsted acid-catalyzed solvent-controlled regioselective hydrothiolation and diastereoselective cascade cyclization of dienes

A highly regio- and diastereo-selective Brønsted acid-catalyzed tandem hydrothiolation/Friedel-Crafts reaction of linear 1,3-dienes has been developed for the first time, which provides a metal-free and atom-economic way of constructing thiochromane derivatives. Meanwhile, by changing the solvent, 4,3-addition hydrothiolation of 1,3-dienes was also discovered. The origin of the observed selectivity was explained by density functional theory calculations.

Role of thiol oxidation by air in the mechanism of the self-initiated thermal thiol–ene polymerization

We highlight the role of thiyl initiating radicals generated by air oxidation of thiols in the mechanism accounting for the self-initiation of thiol–ene polymerization. The driving force of this reaction is polarization of the S–H bond.