Trisulfur-Radical-Anion-Triggered C(sp2)-H Amination of Electron-Deficient Alkenes

Three-Component Assembly of Dihydropyrrolo[3,4-e][1,3]thiazines from Elemental Sulfur, Maleimides, and 1,3,5-Triazinanes

A three-component reaction for the synthesis of dihydropyrrolo[3,4-e][1,3]thiazines has been developed. Elemental sulfur, maleimides, and 1,3,5-triazinanes are assembled together through sulfuration/nucleophilic attack in N-methylpyrrolidin-2-one (NMP) under mild conditions. A small amount of NaHCO3 is important for the activation of the reaction. In this method, sulfur plays a dual role in thiazine ring formation, while triazinanes are utilized as three-atom synthons in the annulation reaction.

A Tandem Regiospecific [3 + 2] Annulation/Ring Cleavage Reaction for the Synthesis of β-Ketoenamides

A series of β-ketoenamines was synthesized from various phenacyl sulfoxides bearing 1-methyl-1H-tetrazole and oximes in moderate to excellent yields. The proposed mechanism involved the generation of α-sulfines from sulfoxides through thermolytic elimination, regiospecific formal [3 + 2] annulations, and elimination of SO2. This protocol provides convenient access to a variety of synthetically valuable N-unprotected β-enaminones with absolute Z selectivity.

Synthesis of 2-benzyl benzoxazoles and benzothiazoles via elemental sulfur promoted cyclization of styrenes with 2-nitrophenols and N,N-dialkyl-3-nitroanilines

Herein we report a method for affording 2-benzyl benzoxazoles from substituted styrenes and 2-nitrophenols. The success of this method relies on the use of simple reagents, namely elemental sulfur and DABCO. A combination of identical reagents was utilized for the annulation of styrenes with N,N-dialkyl-3-nitroanilines to afford 2-benzyl benzothiazoles. Overall, benzoxazoles and benzothiazoles bearing useful functionalities such as halogens, amines, and heterocyclic groups were isolated in moderate to good yields. Our methods are a rare example of divergent transformations of substituted nitroarenes towards 2-benzyl benzoxazoles and benzothiazoles.

Piperine: Chemistry and Biology

Piperine is a plant-derived promising piperamide candidate isolated from the black pepper (Piper nigrum L.). In the last few years, this natural botanical product and its derivatives have aroused much attention for their comprehensive biological activities, including not only medical but also agricultural bioactivities. In order to achieve sustainable development and improve survival conditions, looking for environmentally friendly pesticides with low toxicity and residue is an extremely urgent challenge. Fortunately, plant-derived pesticides are rising like a shining star, guiding us in the direction of development in pesticidal research. In the present review, the recent progress in the biological activities, mechanisms of action, and structural modifications of piperine and its derivatives from 2020 to 2023 are summarized. The structure-activity relationships were analyzed in order to pave the way for future development and utilization of piperine and its derivatives as potent drugs and pesticides for improving the local economic development.

Recent Advances in Alkenyl sp2 C-H and C-F Bond Functionalizations: Scope, Mechanism, and Applications

Alkenes and their derivatives are featured widely in a variety of natural products, pharmaceuticals, and advanced materials. Significant efforts have been made toward the development of new and practical methods to access this important class of compounds by selectively activating the alkenyl C(sp²)-H bonds in recent years. In this comprehensive review, we describe the state-of-the-art strategies for the direct functionalization of alkenyl sp² C-H and C-F bonds until June 2022. Moreover, metal-free, photoredox, and electrochemical strategies are also covered. For clarity, this review has been divided into two parts; the first part focuses on currently available alkenyl sp² C-H functionalization methods using different alkene derivatives as the starting materials, and the second part describes the alkenyl sp² C-F bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the scope, limitations, mechanistic studies, stereoselective control (using directing groups as well as metal-migration strategies), and their applications to complex molecule synthesis where appropriate. Overall, this comprehensive review aims to document the considerable advancements, current status, and emerging work by critically summarizing the contributions of researchers working in this fascinating area and is expected to stimulate novel, innovative, and broadly applicable strategies for alkenyl sp² C-H and C-F bond functionalizations in the coming years.

A stepwise one-pot synthesis of aliphatic thiols and their derivatives from acrylamides and sulfur

Elemental sulfur enables the convenient formation of C-S bonds and the direct incoporation of S-S bonds. The reactivity of easily accessible electron deficient alkenes towards sulfur, however, is barely disclosed. Herein, we investigated the reactivity of acrylamides with sulfur and eventually developed a new pseudo-multicomponent reaction for the preparation of polysulfides. Sequential one-pot reduction led to diversely substituted thiols. Additional third stage one-pot modifications provided thioethers, unsymmetric disulfide and thioester.

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.

Late-Stage Amination of Drug-Like Benzoic Acids: Access to Anilines and Drug Conjugates through Directed Iridium-Catalyzed C-H Activation

The functionalization of C−H bonds, ubiquitous in drugs and drug‐like molecules, represents an important synthetic strategy with the potential to streamline the drug‐discovery process. Late‐stage aromatic C−N bond–forming reactions are highly desirable, but despite their significance, accessing aminated analogues through direct and selective amination of C−H bonds remains a challenging goal. The method presented herein enables the amination of a wide array of benzoic acids with high selectivity. The robustness of the system is manifested by the large number of functional groups tolerated, which allowed the amination of a diverse array of marketed drugs and drug‐like molecules. Furthermore, the introduction of a synthetic handle enabled expeditious access to targeted drug‐delivery conjugates, PROTACs, and probes for chemical biology. This rapid access to valuable analogues, combined with operational simplicity and applicability to high‐throughput experimentation has the potential to aid and considerably accelerate drug discovery.

Synthesis of Deuterated (E)-Alkene through Xanthate-Mediated Hydrogen-Deuterium Exchange Reactions

Herein we have developed a reversible hydrogen-deuterium exchange reaction of nonactivated olefins. By using EtOCS₂K as a mediator, the H/D exchange reaction was realized through repeated addition and elimination reactions, demonstrating reversible H/D exchange between ordinary olefins and deuterated olefins. Using the lowest cost D₂O without precious metal catalysts and ligands, a broad spectrum of compatibility of functional groups was achieved.