Copper-Catalyzed and Air-Mediated Mild Cross-Dehydrogenative Coupling of Aryl Thioureas and Dialkyl H-Phosphonates: The Synthesis of Thiophosphonates

Selective Construction of C-S/S-N Bonds from N-Substituted O-Thiocarbamates and Indoles under Transition-Metal-Free Conditions

A method for the selective construction of S-N/C(sp2)-S bonds using N-substituted O-thiocarbamates and indoles as substrates is reported. This protocol features good atom utilization, mild conditions, short reaction time, and wide substrate scope, which can provide a convenient path for the functionalization of indoles. In addition, the reaction could be scaled up on gram scale, showing potential application value in industry synthesis.

Copper-Catalyzed Multicomponent Reactions of Intramolecular and Intermolecular Thiotrifluoromethylation of Alkenes: Access to CF3-Containing 2-Iminothiazolidines and Isothioureas

A copper-catalyzed multicomponent reaction of secondary amines bearing allyl substitution, isothiocyanates, and Togni reagent II has been developed under Cs₂CO₃ in DCE at 75 °C. An intermolecular multicomponent reaction of thioureas, activated and unactivated alkenes, and Togni reagent II has also been developed under DMAP in acetonitrile at room temperature. These two alkene difunctionalization reactions provide CF₃-containing 2-iminothiazolindines and isothioureas in moderate to excellent yields with broad substrate scope and good functional group tolerance, respectively.

Coupling of 1-Chloro-N,N-diisopropylphosphanamine-Based Reagents with Alcohols and Thiosulfonates: A Precise Construction of O-P(O)-S Bonds

Herein, we present the first mild, one-step direct synthesis of mixed phosphorothioates through selective generation of O-P(O)-S bonds at rt under additive-free condition. Further, reactions of different model natural products with 1,1-dichloro-N,N-diisopropylphosphanamine helped to present an alternative dimerization strategy. The synthetic utility of the methodology was extended for the synthesis of mixed phosphoroselenoates as well. The potential of the reaction was further demonstrated for the synthesis of mixed phosphorothioate bearing two different alcohols.

Photoinduced Decarboxylative Phosphorothiolation of N-Hydroxyphthalimide Esters

A visible-light-induced protocol for the synthesis of phosphorothioates is developed by employing the Ir-catalyzed decarboxylative phosphorothiolation of N-hydroxyphthalimide esters. This novel synthesis method utilizes carboxylic acids as raw material, which is stable, cheap, and commercially available. Scope studies show that this reaction has good compatibility of functional groups. Notably, both the synthesis of steric hindrance phosphorothioates and the later modification of some bioactive compounds are successfully achieved.

Cs2CO3-Promoted Hydrothiolation of Alkynes with Aryl Thioureas: Stereoselective Synthesis of (Z)-Vinyl Sulfides

A metal-free Cs₂CO₃-promoted hydrothiolation of alkynes with aryl thioureas for stereoselective synthesis of (Z)-vinyl sulfides has been reported. Vinyl thioethers were obtained without a metal catalyst in good yields via anti-Markovnikov and cis addition. The protocol features a broad substrate scope of the starting materials, high atom economy, good yields, and exclusive stereoselectivity, showing potential synthetic value for the synthesis of a diversity of (Z)-vinyl thioethers.

Palladium-Catalyzed Q-Tube-Assisted Protocol for Synthesizing Diaza-dibenzo[a,e]azulene and Diaza-benzo[a]fluorene Derivatives via O2 Acid-Promoted Cross-Dehydrogenative Coupling

An appropriate and efficient Q-tube-assisted palladium-catalyzed strategy for the synthesis of novel, unparalleled diaza-dibenzo[a,e]azulene and diaza-benzo[a]fluorene derivatives has been sophisticated, which includes oxygen and AcOH-induced oxidative C(sp³)-C(sp²) cross-dehydrogenative coupling reactions of 1-amino-2-imino-4-arylpyridine-3-carbonitriles with benzocyclic ketones such as benzosuberone, tetralone, thiochromone, and chromone, respectively. This Q-tube gas purging kit assisted-protocol features safe due to easy pressing and sealing, a wide substrate scope, easy workup and purifying phases, and the use of O₂ as a benign oxidant, in addition to being scalable and having a high atom economy. The suggested mechanistic pathway includes a formal dehydrative step followed by palladium AcOH-induced CH(sp³)-CH(sp²) oxidative cross-coupling. In this study, X-ray crystallographic analysis has been used to authenticate the targeted products.

Domino Synthetic Strategy for Tetrahydrothiopyran Derivatives from Benzaldehydes, 2-Acetylfuran/2-Acetylthiophene, and Sodium Sulfide

A novel domino reaction from benzaldehydes and 2-acetylfuran/2-acetylthiophene with sodium sulfide was developed to synthesize a series of tetrahydrothiopyran (THTP) derivatives. The reaction proceeded well to construct a tetrahydrothiopyran ring and five new bonds in one step. A mechanism is proposed, involving a stepwise Aldol/double Michael addition/Aldol (AMMA) reaction cascade. In this transformation, sodium sulfide acts as a nucleophile and base. This method is characterized by transition-metal-free, commercially available starting materials and mild reaction conditions.

A Mild Synthesis of 2-Substituted Benzothiazoles via Nickel-Catalyzed Intramolecular Oxidative C-H Functionalization

A highly efficient synthetic method for the preparation of 2-aminobenzothiazoles starting from arylthioureas has been reported. By using a nickel catalyst, arylthioureas undergo intramolecular oxidative C-H bond functionalization, giving the desired 2-aminobenzothiazoles in good to excellent yields. This protocol features an inexpensive catalyst, low catalyst loading, mild reaction conditions, a short reaction time, and good to excellent yields, and it can be scaled up easily to a gram scale with almost no yields decreasing.

Synthetic Strategy for Pyrazolo[1,5-a]pyridine and Pyrido[1,2-b]indazole Derivatives through AcOH and O2-Promoted Cross-dehydrogenative Coupling Reactions between 1,3-Dicarbonyl Compounds and N-Amino-2-iminopyridines

An efficient method has been developed for the synthesis of uniquely substituted pyrazolo[1,5-a]pyridine and pyrido[1,2-b]indazole derivatives, which involves acetic acid and molecular oxygen promoted cross-dehydrogenative coupling reactions of respective β-ketoesters and β-diketones (like ethyl acetoacetate, ethyl benzoylacetate, methyl propionylacetate, acetylacetone, dimedone, 1,3-cyclohexanedione, and 1,3-cyclopentanedione) with N-amino-2-iminopyridines. The proposed tentative mechanism involves formal acetic acid-promoted oxidative C(sp3)-C(sp2) dehydrogenative coupling followed by dehydrative cyclization under a catalyst-free condition within high atom economy processes.

Sustainable Synthetic Approach for (Pyrazol-4-ylidene)pyridines By Metal Catalyst-Free Aerobic C(sp2)-C(sp3) Coupling Reactions between 1-Amino-2-imino-pyridines and 1-Aryl-5-pyrazolones

A novel, metal catalyst-free, and efficient method has been developed for the synthesis of (pyrazol-4-ylidene)pyridine derivatives. The process involves dehydrogenative coupling of 1-amino-2-imino-pyridines with 1-aryl-5-pyrazolone derivatives utilizing O2 as the sole oxidant. The new method benefits from a high atom economy, efficiency, and substrate scope, as well as the simplicity of reaction and product purification procedures.