One-step construction of unsymmetrical thioureas and oxazolidinethiones from amines and carbon disulfide via a cascade reaction sequence

Regioselective synthesis of 2-aminophenols from N-arylhydroxylamines

A novel strategy for the synthesis of 2-aminophenols in the absence of metals and oxidants was described. The 2-aminophenols were efficiently obtained through a cascade [3,3]-sigmatropic rearrangement and in situ hydrolysis process by using readily available N-arylhydroxylamines and the in situ-generated methyl chlorosulfonate from commercially available sulfuryl chloride and methanol under mild conditions. This method could be scaled up and has a wide substrate scope with great functional group tolerance and high regioselectivity. The 2-aminophenol products could be readily converted into structurally diverse functional molecules in good yields under various conditions.

Visible-Light-Promoted Cascade Coupling of 2-Isocyanonaphthalenes with Elemental Sulfur and Amines to Construct Naphtho[2,1-d]thiazol-2-Amines

A visible-light-induced strategy has been explored for the synthesis of naphtho[2,1-d]thiazol-2-amines through ortho-C-H sulfuration of 2-isocyanonaphthalenes with elemental sulfur and amines under external photocatalyst-free conditions. This three-component reaction, which utilizes elemental sulfur as the odorless sulfur source, molecular oxygen as the clean oxidant, and visible light as the clean energy source, provides a mild and efficient approach to construct a series of naphtho[2,1-d]thiazol-2-amines. Preliminary mechanistic studies indicated that visible-light-promoted photoexcitation of reaction intermediates consisting of thioureas and DBU might be involved in this transformation.

Sulfur- and Amine- Promoted Multielectron Autoredox Transformation of Nitromethane: Multicomponent Access to Thiourea Derivatives

Thiourea derivatives are in-demand motifs in organic synthesis, medicinal chemistry and material science, yet redox methods for the synthesis that start from safe, simple, inexpensive and readily available feedstocks are scarce. In this article, we disclose the synthesis of these motifs using elemental sulfur and nitromethane as the starting materials. The method harnesses the multi-electron auto-redox property of nitromethane in the presence of sulfur and amines, delivering thiourea products without any added oxidant or reductant. Extension of this reaction to cyclizable amines and/or higher homologues of nitromethane led to a wide range of nitrogen heterocycles and thioamides. Operationally simple, the reactions are scalable, tolerate a wide range of functional groups, and can be employed for the direct functionalization of natural products. Mechanistically, the nitro group was found to act as an oxidant leaving group, being reduced to ammonia whereas sulfur, along with the role of a sulfur building block for the thiocarbonyl group, behaved as a complementary reductant, being oxidized to sulfate.

Synthesis of Asymmetric Urea Derivatives from COS and Amines: Substrate Selection, Scope Studies, and Mechanism Investigation

A series of asymmetric ureas were synthesized by a one-pot reaction of amines and carbonyl sulfide (COS) under catalyst-free conditions. The highly selective synthesis of asymmetric urea was successfully achieved by the use of weakly nucleophilic aromatic amines and highly nucleophilic secondary aliphatic amines. Moreover, a reaction mechanism was proposed based on the detailed NMR and FTIR study. This efficient synthetic methodology provides a mild and selective method for synthesizing asymmetric urea derivatives.

One-Pot Synthesis of Thio-Augmented Sulfonylureas via a Modified Bunte's Reaction

We report the development of a one-pot Bunte's reaction-enabled expeditious platform under aqueous conditions for the scalable conversion of sulfonylureas to synthetically versatile thio-sulfonylureas. The reaction was further propagated in the same pot to yield diverse chiral and achiral isothiosulfonyl analogs. The protocol enabled the synthesis of various drug-like molecules and was applied to an enantiomeric synthesis of a cannabinoid receptor antagonist SLV326.

Regulation of Tyrosinase Enzyme Activity by Glutathione Peroxidase Mimics

Hydrogen peroxide plays a crucial role in the melanogenesis process by regulating the activity of the key melanin-forming enzyme tyrosinase, responsible for the browning of fruits, vegetables, and seafood. Therefore, a molecule with dual activities, both efficient tyrosinase inhibition and strong hydrogen peroxide degrading ability, may act as a promising antibrowning agent. Herein, we report highly efficient selone-based mushroom tyrosinase inhibitors 2 and 3 with remarkable glutathione peroxidase (GPx) enzyme-like activity. The presence of benzimidazole moiety enhances the tyrosinase inhibition efficiency of selone 2 (IC₅₀ = 0.4 μM) by almost 600 times higher than imidazole-based selone 1 (IC₅₀ = 238 μM). Interestingly, the addition of another aromatic ring to the benzimidazole moiety has led to the development of an efficient lipid-soluble tyrosinase inhibitor 3 (IC₅₀ = 2.4 μM). The selenium center and the -NH group of 2 and 3 are extremely crucial to exhibit high GPx-like activity and tyrosinase inhibition potency. The hydrophobic moiety of the inhibitors (2 and 3) further assists them in tightly binding at the active site of the enzyme and facilitates the C═Se group to strongly coordinate with the copper ions. Inhibitor 2 exhibited excellent antibrowning and polyphenol oxidase inhibition properties in banana and apple juice extracts.

Electroreductive synthesis of polyfunctionalized pyridin-2-ones from acetoacetanilides and carbon disulfide with oxygen evolution

A chemical reductant or a sacrificial electron donor is required in any reduction reactions, generally resulting in undesired chemical waste. Herein, we report a reductant-free reductive [3 + 2 + 1] annulation of β-keto amides with CS₂ enabled by the synergy of electro/copper/base using water as an innocuous anodic sacrifice with O₂ as a sustainable by-product. This electrochemical protocol is mild and provides access to polyfunctionalized pyridin-2-ones from simple starting materials in a single step.

Catalyst-free aziridine-based step-growth polymerization: a facile approach to optically active poly(sulfonamide amine)s and poly(sulfonamide dithiocarbamate)s

Step-growth polymerization of chiral bis(N-sulfonyl aziridine)s with diamines or bis(dialkyldithiocarbamate) in the absence of a catalyst allows the facile synthesis of optically active polysulfonamide derivatives.

Synthesis of Thiocarbamoyl Fluorides and Isothiocyanates Using Amines with CF3SO2Cl

A practical and efficient method to synthesize thiocarbamyl fluorides and isothiocyanates from amines with trifluoromethanesulfonyl chloride was developed. In the presence of the reducing agent triphenylphosphine and sodium iodide, thiocarbamyl fluorides and isothiocyanates were synthesized from secondary/primary amine in moderate to excellent yields, respectively. A broad scope of substrates and good functional group compatibility were observed.