NAD(P)H Models 20: Chemoselective metal ion catalyzed reduction of α-keto-β,γ-unsaturated esters by 1,4-dihydropyridine derivatives

Ethyl 2-oxo-4-aryl-3-butene-1-oates 1a–1c are reduced by NAD(P)H models (1-n-propyl-1,4-dihydronicotinamide (4) and Hantzsch ester(5)), in presence of magnesium perchlorate. One equivalent of the reductant reduces the substrates selectively to the corresponding 2-oxo-4-arylbutanoates (6,10a,b). An additional equivalent and higher temperature, converts ethyl 2-oxo-4-phenylbutanoate (6) to ethyl 2-hydroxy-4-phenylbutanoate (7). Reduction of ethyl 2-oxo-4-phenyl-3-buten-1-oate (1a) by Hantzsch ester in C₂H₅OD or by Hantzsch ester-4,4-d₂ in C₂H₅OH, leads to direct transfer of the hydrogen or deuterium, respectively, without isotopic scrambling. These results have been interpreted to support the hydride transfer mechanism.     

An InCl3 catalyzed facile one-pot synthesis of novel dispiro[cyclopent-3′-ene]bisoxindoles

An InCl₃ catalyzed efficient synthesis of novel dispiro[cyclopent-3′-ene]bisoxindoles is accomplished via a one-pot reductive cyclization of isatylidene malononitriles using the Hantzsch ester.     

CBr4： A Useful and Efficient Catalyst for One-Pot Synthesis of 4-Substituted-1,4,5,6,7,8-Hexahydroquinolin-5-ones Via Hantzsch Reaction

A carbon tetrabromide （CBr4） catalyzed one-pot synthesis of 4-substituted-1,4,5,6,7,8-hexahydroquinolin-5-one derivatives via a Hantzsch reaction under mild conditions was described.     

KHSO4 Supported Onto Bentonite,A Versatile Reagent for Aromatization of Hantzsch 1,4‐Dihydropyridines

Aromatization of Hantzsch 1,4‐dihydropyridines was promoted by KHSO₄, a relatively green chemical, supported onto bentonite to yield the corresponding pyridine derivatives in excellent yields. The reaction was carried out under mild and convenient conditions.     

Aromatization of Hantzsch Ester 1,4‐Dihydropyridines with Iodine under Normal Conditions and Ultrasound Irradiation

A variety of Hantzsch ester 1,4‐dihydropyridines are efficiently oxidized to their corresponding pyridine compounds with iodine under normal conditions and ultrasound irradiation. The reactions were carried out in refluxing CH₃CN.     

Iridium-catalyzed asymmetric transfer hydrogenation of quinolines with Hantzsch esters

The iridium-catalyzed enantioselective transfer hydrogenation of quinolines with Hantzsch esters was developed with up to 88% ee using [Ir(COD)Cl]₂/(S)-SegPhos/I₂ as a catalyst.     

K2CO3-assisted one-pot sequential synthesis of 2-trifluoromethyl-6-difluoromethylpyridine-3,5-dicarboxylates under solvent-free conditions

A novel synthesis of 2-trifluoromethyl-6-difluoromethylpyridine-3,5-dicarboxylates by three-component reaction of ethyl trifluoroacetoacetate, aldehydes, and ammonium acetate in the presence of K₂CO₃ under solvent-free conditions via sequential Hantzsch reaction/dehydration/dehydrofluorination in a one-pot process was described.     

Brønsted Acid Ionic Liquid [(CH2)4SO3HMIM][HSO4] as Novel Catalyst for One-Pot Synthesis of Hantzsch Polyhydroquinoline Derivatives

1-(4-Sulfonic acid)butyl-3-methylimidazolium hydrogen sulfate ([(CH₂)₄SO₃HMIM][HSO₄]) efficiently catalyzed a four-component Hantzsch reaction of aldehyde, ethylacetoacetate, dimedone, and ammonium acetate to afford the corresponding polyhydroquinoline derivatives.     

New Efficient Protocol for the Production of Hantzsch 1,4-Dihydropyridines Using RuCl3

Hantzsch 1,4-dihydropyridines are synthesized in a few minutes and in good to excellent yields from aldehydes, 1,3-dicarbonyl compounds, and ammonium acetate. The reaction is performed in solvent-free conditions, and 5 mol% of RuCl₃ is enough for this protocol.     

Catalytic Asymmetric Reductive Condensation of N–H Imines: Synthesis of C2‐Symmetric Secondary Amines

A highly diastereoselective and enantioselective Brønsted acid catalyzed reductive condensation of N?H imines was developed. This reaction is catalyzed by a chiral disulfonimide (DSI), uses Hantzsch esters as a hydrogen source, and delivers useful C₂‐symmetric secondary amines.     

Ruthenium‐Catalyzed Transfer‐Hydrogenative Cyclization of 1,6‐Diynes with Hantzsch 1,4‐Dihydropyridine as a H2 Surrogate

The transfer‐hydrogenative cyclization of 1,6‐diynes with Hantzsch 1,4‐dihydropyridine as a H₂ surrogate was performed in the presence of a cationic ruthenium catalyst of the type [Cp′Ru(MeCN)₃PF₆]. Exocyclic 1,3‐dienes or their 1,4‐hydrogenation products, cycloalkenes, were selectively obtained, depending on the substrate structure and the reaction conditions.     

An efficient aerobic oxidative aromatization of Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines

4-Substituted Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines were oxidized to the corresponding pyridines and pyrazoles, respectively, in high yields by molecular oxygen in the presence of catalytic amount of N-hydroxyphthalimide (NHPI) and Co(OAc)₂ in acetonitrile at room temperature.     

One‐Pot Synthesis of Hantzsch Pyridines via NH4I Promoted Condensation of 1,3‐Dicarbonyl Compounds with DMSO and NH4OAc

A one‐pot synthesis of Hantzsch pyridines was achieved through NH₄I‐promoted condensation of 1,3‐dicarbonyl compounds with DMSO and NH₄OAc, in which the C4 of the pyridine rings was derived from DMSO and the nitrogen atom resulted from NH₄OAc and NH₄I. The target product could be obtained in moderate to excellent yields.     

Silica-supported perchloric acid (HClO4–SiO2): a mild, reusable and highly efficient heterogeneous catalyst for multicomponent synthesis of 1,4-dihydropyridines via unsymmetrical Hantzsch reaction

Facile synthesis of some 1,4-dihydropyridine derivatives via Hantzsch reaction of 5,5-dimethyl-1,3-cyclohexanedione (dimedone), 1,3-diphenyl-2-propen-1-one derivatives and ammonium acetate under solvent-free condition in the presence of silica-supported perchloric acid (HClO₄–SiO₂) is described. The catalyst is easily prepared, stable, reusable and efficient under the reaction conditions.     

High efficient iron-catalyzed transfer hydrogenation of quinolines with Hantzsch ester as hydrogen source under mild conditions

A highly efficient transfer hydrogenation of quinolines with Hantzsch ester as hydrogen source in the presence of 1 mol% Fe(OTf)₂ under mild conditions has been developed. A series of substituted 1,2,3,4-tetrahydroquinoline derivatives were afforded in excellent yields with good functional group tolerance.     

Efficient one-pot synthesis of polyhydroquinoline derivatives using Cs2.5H0.5PW12O40 as a heterogeneous and reusable catalyst in molten salt media

Polyhydroquinoline derivatives have been prepared efficiently in a one-pot synthesis via Hantzsch condensation using Cs_2.5H_0.5PW₁₂O₄₀ as a heterogeneous and reusable catalyst. The present method uses molten salt media instead of hazardous organic solvents. The present methodology offers several advantages such as simple procedure, excellent yields, and a short reaction time.     

Synthesis of 1,4-Dihydropyridines Using Ce(SO_4)_2-SiO_2 as Catalyst under Solvent-free Conditions

A facile and efficient one‐pot synthesis of 1,4‐dihydropyridines from aldehyde, 1,3‐dicarbonyl compounds and ammonium acetate in the presence of Ce(SO₄)₂‐SiO₂ at 80°C under solvent‐free conditions is described. Compared with the classical Hantzsch reaction, this novel method consistently has the advantages of excellent yields and short reaction time.     

Facile Yb(OTf)3 promoted one-pot synthesis of polyhydroquinoline derivatives through Hantzsch reaction

Yb(OTf)₃ catalyzed efficient Hantzsch reaction via four-component coupling reactions of aldehydes, dimedone, ethyl acetoacetate and ammonium acetate at ambient temperature was described as the preparation of polyhydroquinoline derivatives. The process presented here is operationally simple, environmentally benign and has excellent yield. Furthermore, the catalyst can be recovered conveniently and reused efficiently.     

Rapid and efficient aromatization of Hantzsch 1,4-dihydropyridines with Potassium peroxomonosulfate catalyzed by manganese(III) Schiff base complexes

Rapid and efficient oxidation of Hantzsch 1,4-dihydropyridine with Potassium peroxomonosulfate is reported. The Mn(III)-salophen/monopersulfate catalytic system converts 1,4-dihydropyridines to their corresponding pyridine derivatives at room temperature in a 1:1, CH₃CN/H₂O mixture. The ability of various Schiff base complexes in the oxidation of 1,4-dihydropyridine was also investigated.     

二氧化锡纳米粒子催化四组分Hantzsch缩合合成多氢喹啉衍生物(英文)

Tin dioxide (SnO2 ) nanoparticles efficiently catalyzed unsymmetrical four-component Hantzsch condensations of various aldehydes, dimedone, ethyl acetoacetate, and ammonium acetate to form polyhydroquinoline derivatives in excellent yields. This novel method offers several advantages over the traditional method of synthesizing these compounds, including safety, mild conditions, short reaction times, high yields, and an easy workup.