One-Pot Tandem/Spirocyclization Reaction: Synthesis of Spiro[pyridine-thiazolidine] Ring Derivatives.

An efficient one-pot, three-component approach was devised to synthesize spiro[pyridine-thiazolidine] ring skeletons using thiazole salts, aldehydes, and enaminones. This method allows the assembly of structurally diverse spiroazepines through [3 + 1 + 2] tandem/spirocyclization reactions. This spirocyclization reaction offers several advantages, including transition metal-free conditions, high chemoselectivity, and the ability to construct structurally novel polycyclic compounds.

Bifunctionalization of styrene through ring-opening-recombination strategy of phenylpropathiazole salt.

By opening the ring of a benzothiazole salt, we provide a sulfur source for the bifunctional reaction of styrene. The ring-opening-recombination reaction of the benzothiazole salt simultaneously constructs new C-S, C-O, and CO bonds after C-S bond breaking. The reaction proceeds in green solvents, requires no transition metal catalyst, and is compatible with many functional groups.

Nucleophilic Dearomatization Strategy to Synthesize Disubstituted 3-Isoquinolinones under Transition Metal-Free Conditions.

Herein, a one-pot protocol for constructing the disubstituted isoquinolinone derivatives via the three-component reactions of 3-haloisoquinolines, alkyl halides, and indoles under transition-metal-free conditions is described. The reaction realized the trifunctionalization of isoquinoline via a dearomatization strategy, which displayed high chemical selectivity, excellent functional group tolerance, and a wide range of substrates, and is environmentally friendly. The three-component coupling involves the construction of new C-N, C═O, and C-C bonds in one step.

Copper-Promoted N-Alkylation and Bromination of Arylamines/Indazoles Using Alkyl Bromides as Reagents for Difunctionalization.

Practical copper-promoted N-alkylation and bromination of arylamines/indazoles with alkyl bromides are described; the N-alkylation-C-4-bromination and N-dialkylation-C-4-bromination of arylamines, and N-alkylation-C-3-bromination of indazoles, with alkyl bromides have been analyzed. The full use of alkyl bromides as alkylating and brominating building blocks without atom wastage, indicating excellent atom and step economy, has been highlighted. Eco-friendly oxygen and water are the reaction oxidant and byproduct, respectively.

Rapid assembly of α-ketoamides through a decarboxylative strategy of isocyanates with α-oxocarboxylic acids under mild conditions.

A simple and practical method for α-ketoamide synthesis via a decarboxylative strategy of isocyanates with α-oxocarboxylic acids is described. The reaction proceeds at room temperature under mild conditions without an oxidant or an additive, showing good substrate scope and functional compatibility. Moreover, the applicability of this method was further demonstrated by the synthesis of various bioactive molecules and different application examples through a two-step one-pot operation.

Hydrogen-Transfer-Mediated N-Arylation of Naphthols Using Indolines as Hydrogen Donors.

Using a hydrogen-transfer-mediated activation mode, we report a new catalytic system for the transfer hydrogenation of naphthols. In the presence of the Pd/C catalyst and base, various naphthols reacted with indolines to afford N-aryl-substituted heterocyclic compounds. Indolines were found to act as novel hydrogen donors for naphthols under palladium catalysis. This method features good functional tolerance, operational simplicity, and a readily available catalyst.

Metal-Free Oxidative Esterification of Ketones and Potassium Xanthates: Selective Synthesis of α-Ketoesters and Esters.

A novel and efficient oxidative esterification for the selective synthesis of α-ketoesters and esters has been developed under metal-free conditions. In the protocol, various α-ketoesters and esters are available in high yields from commercially available ketones and potassium xanthates. Mechanistic studies have proven that potassium xanthate not only promotes oxidative esterification but also provides an alkoxy moiety for the reaction, which involves the cleavage and reconstruction of C-O bonds.

Direct electrochemical reductive amination between aldehydes and amines with a H/D-donor solvent.

A novel electrochemical synthesis protocol has been achieved for reductive amination between aldehydes and amines in undivided cells at room temperature. Under metal-free and external-reductant-free electrolysis conditions, various important secondary amine products are obtained in moderate-to-high yields. Deuterium-labeling experiments have demonstrated that low-toxicity DMSO acts both as a solvent and a H-donor in the reaction. On this basis, various deuterium-labeled products with good-to-excellent D-incorporation have been synthesized by using DMSO-d6 as a solvent. Furthermore, a molecule with GR-antagonistic activity has been synthesized through further sulfonylation.

Synthesis of N-Biheteroarenes via Acceptorless Dehydrogenative Coupling of Benzocyclic Amines with Indole Derivatives.

Here, via a strategy of in situ capture of partially dehydrogenated cyclic amine motifs, we present an acceptorless dehydrogenative coupling of benzocyclic amines with indole derivatives that enables to access various quinoline-indole linked N-biheteroarenes in an efficient manner. The catalytic transformation is characteristic of operational simplicity, a readily available catalyst system, good substrate and functional compatibility, mild conditions, high atom efficiency, and no need for oxidant and halogenated coupling agents.

Electrochemical Synthesis Strategy for Cvinyl-CF3 Compounds through Decarboxylative Trifluoromethylation.

An efficient decarboxylative trifluoromethylation of α,ß-unsaturated carboxylic acids using the Langlois reagent as a trifluoromethyl precursor has been achieved by an electro-oxidative strategy. Under catalyst-free and external oxidant-free electrolysis conditions, a series of Cvinyl-CF3 compounds are obtained with a high regioselectivity in good yields. The successful trapping of the CF3 radical by a scavenger has confirmed that radical processes are involved in this system.

Transition metal-free α-methylation of 1,8-naphthyridine derivatives using DMSO as methylation reagent.

A practical approach to the direct α-methylation of 1,8-naphthyridines under mild reaction conditions has been developed using simple and readily available DMSO as a convenient and environmentally friendly carbon source. This method is transition metal-free and highly chemoselective, shows good functional group tolerance, and uses DMSO as a methyl source, providing efficient and rapid access to an important compound class, 2-methyl-1,8-naphthyridines.

Direct access to bis-S-heterocycles via copper-catalyzed three component tandem cyclization using S8 as a sulfur source.

A novel strategy for constructing sulfur containing bis-S-heterocyclic compounds from oxime esters/vinyl azide, phenylacetylene/aldehydes and elemental sulfur (S8) has been developed. These transformations show good functional group tolerance. Various bis-S-heterocyclic products were efficiently synthesized from easily prepared or widely commercially available starting materials. In this protocol, S8 successfully served as a two-sulfur atom donor for thiophene and thiazole rings, respectively.

(Z)-Tetrahydrothiophene and (Z)-tetrahydrothiopyran synthesis through nucleophilic substitution and intramolecular cycloaddition of alkynyl halides and EtOCS2K.

This protocol provides a novel, environmentally friendly and simple method for the synthesis of (Z)-tetrahydrothiophene derivatives using the nucleophilic thiyl radical intramolecular cycloaddition cascade process to construct C-S bonds under transition-metal-free conditions. This transformation process offers a broad substrate scope, good functional group tolerance, and excellent stereoselectivity (Z/E ratios up to 99/1). Moreover, the process uses odourless, stable and cheap EtOCS2K as the sulfur source.

Regioselective C-H Bond Alkynylation of Carbonyl Compounds through Ir(III) Catalysis.

Selective C-H bond alkynylation toward modular access to material and pharmaceutical molecules is of great desire in modern organic synthesis. Reported herein is Ir(III)-catalyzed regioselective C-H alkynylation of ketones and esters, which is generally applicable for the rapid construction of molecular complexity. This protocol provides a complementary process for conventional alkyne synthesis. Further functionalization of carbonyl-derived material molecules and pharmaceuticals demonstrates the potential synthetic utility of this methodology.

Copper-Catalyzed Cyanation of N-Tosylhydrazones with Thiocyanate Salt as the "CN" Source.

A novel protocol for the synthesis of α-aryl nitriles has been successfully achieved via a copper-catalyzed cyanation of N-tosylhydrazones employing thiocyanate as the source of cyanide. The features of this method include a convenient operation, readily available substrates, low-toxicity thiocyanate salts, and a broad substrate scope.

Palladium-Catalyzed C-H Functionalization of Aromatic Oximes: A Strategy for the Synthesis of Isoquinolines.

An efficient strategy for synthesis of isoquinolines via Pd(II)-catalyzed cyclization reaction of oximes with vinyl azides or homocoupling of oximes is reported. Oximes could serve as a directing group and an internal oxidant in the transformation. This reaction features good functional group tolerance and provides a useful protocol for the synthesis of different kinds of isoquinolines under mild conditions. Some control experiments and (15)N isotope labeling experiments were conducted for the mechanistic research.

Access to Thiazole via Copper-Catalyzed [3+1+1]-Type Condensation Reaction under Redox-Neutral Conditions.

A new strategy for thiazoles via copper-catalyzed [3+1+1]-type condensation reaction from oximes, anhydrides and potassiumthiocyanate (KSCN) is developed herein. The transformation has good functional group tolerance and various thiazoles were formed smoothly in good to excellent yields under mild reaction conditions. This process involves copper-catalyzed N-O/C-S bond cleavages, activation of vinyl sp2 C-H bond, and C-S/C-N bond formations which are under redox-neutral conditions as well as operational simplicity.

Palladium-catalyzed tandem annulation: a strategy to construct 2,3-difunctionalized benzofuran derivatives in ionic liquids.

An efficient and ecofriendly method for the construction of 2,3-difunctionalized benzofuran derivatives in moderate to good yields from readily available 2-alkynylphenols has been developed. This tandem annulation process, featuring one pot, three steps, good functional group tolerance, and high atom economy, makes this transformation efficient and practical. Moreover, this protocol is scalable, illustrating its potential applications in synthetic and pharmaceutical chemistry.

AgNOx as Nitrogen Source for [1+1+3] Cycloaddition of Isocyanides with Isocyanates: Selective Synthesis of 1,2,4-Triazoles.

A novel [1+1+3] annulation of AgNOx, isocyanides, and isocyanates for the selective synthesis of 1,2,4-triazoles is presented herein. In this transformation, AgNOx and isocyanates are used as nitrogen sources instead of the traditional hydrazine or diazonium reagents. This process also involves N-O/C-H/C═N bond cleavage and the construction of new N-N/C-N bonds with a good substrate scope and functional group tolerance.

In Situ Activation of Azaarenes and Terminal Alkynes to Construct Bridged Polycyclic Compounds Containing Isoquinolinones.

A copper-catalyzed [4+2] cyclization reaction of isoquinolines and alkynes is developed for the one-step construction of isoquinolinone derivatives with multisubstituted bridging rings. The unique feature of this three-component tandem cyclization reaction is the functionalization of the C1, N2, C3, and C4 positions of 3-haloisoquinolines via the construction of new C-N, C═O, and C-C bonds. This dearomatization strategy for the synthesis of structurally complex isoquinolinone-bridged cyclic compounds offers good chemoselectivity, broad functional group compatibility, greenness, and high step economy.