An efficient and solvent-free one-pot synthesis of 1,4-dihydropyridines under microwave irradiation

An efficient synthesis of 1,4-dihydropyridines using lanthanum oxide as a catalyst from aldehydes,β-ketoester and ammonium acetate without solvent under the irradiation of microwave is described.Compared with the classical Hantzsch reaction,this new method has the advantage of good yield(90-98%) and short reaction time(40-80 s).     

Co纳米粒子催化无溶剂条件下一锅四组分法高效合成1,4-二氢吡啶衍生物(英文)

A straightforward and general method has been developed for the synthesis of C5-unsubstitiuted 1,4-dihydropyridines by a reaction using dimedone, acetophenone, aromatic aldehydes, and ammonium acetate in the presence of a catalytic amount of Co nanoparticles as a heterogeneous and eco-friendly catalyst with high catalytic activity at room temperature under solvent-free conditions. This catalyst is easily separated by magnetic devices and can be reused without any apparent loss of activity for the reaction. In addition, it is very interesting that when using Co nanoparticles as a catalyst, spatially-hindered aldehydes such as 2-methoxy-, 2-fluoro-, and 2-chloro-aldehydes are suitable for this reaction.     

Synthesis and Crystal Structure of Ethyl 2,7,7-Trimethyl-4-(4''''-methylphenyl)- 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3- carboxylate in Aqueous Medium

1 INTRODUCTION The 1,4-dihydropyridines (1,4-DHPs) are biologi- cally interesting compounds and have been developed extensively in pharmacology. 1,4-DHP derivatives are used therapeutically in the treatment of cardio- vascular disorders, especially hypertension and coro- nary heart disease such as angina pectoris, atheros- clerosis, etc. The DHPs have emerged as one of the most important classes of drugs for the treatment of gastrointestinal disease, Raynaud?s disease, pulmonary hyper…     

Oxidative aromatization of Hantzsch 1,4-dihydropyridines by aqueous hydrogen peroxide-acetic acid

A simple method for the oxidative aromatization of Hantzsch 1,4-dihydropyridines to the corresponding pyridines is achieved by using hydrogen peroxide as green oxidant and acetic acid as catalyst in aqueous solution.     

Microwave assisted synthesis of novel Hantzsch 1,4-dihydropyridines, acridine-1,8-diones and polyhydroquinolines bearing the tetrazolo[1,5-a]quinoline moiety and their antimicrobial activity assess

Microwave assisted efficient Hantzsch reaction via four-component coupling reactions of tetrazolo[1,5-α]quinoline-4-carbal-dehyde, dimedone/cyclohexane-1,3-dione,ethyl/methyl acetoacetate and ammonium acetate was described as the preparation of tetrazolo[1,5-α]quinoline based 1,4-dihydropyridines,acridine-1,8-diones and polyhydroquinolines.The process presented here is simple,rapid,environmentally welcoming and high yielding.All the derivatives were subjected to an in vitro antimicrobial screening against a representative panel of bacteria and fungi and results worth further investigations.     

Solid State Oxidative Aromatization of Hantzsch 1,4-Dihydropyridines to Pyridines Using Iodobenzene Diacetate or Hydroxy(tosyloxy)iodobenzene

An easy, safe, solvent-free and effective method for oxidative aromatization of Hantzsch 1,4-dihydropyridines catalyzed by hypervalent iodine (IBD and HTIB) to corresponding pyridine derivatives in high yields within short span of time. All reactions were carried out just by grinding the two reactants.     

Novel Reaction of Nitroxide with Hantzsch Dihydropyridines

Nitroxides have been found to be the intermediate in the in vivo metabolism of hydroxamic acid, a well-known biological molecule1. Structural modification of some antitumor drugs by introducing nitroxides can lower toxicity remarkably with retention or even increase of the antitumor activity2. Furthermore, the use of nitroxides as spin probes makes it possible to get information regarding the microenvironment of the reaction. 4-Substituted Hantzsch 1,4-dihydropyridines (DHP) are analogs …     

Synthesis of Benzofuran-fused 1,4-Dihydropyridines via Bifunctional Squaramide-catalyzed Formal [4+2] Cycloaddition of Azadienes with Malononitrile

An efficient bifunctional squaramide-catalyzed Michael addition/cyclization of azadienes with malononitrile has been successfully developed,providing a facile access to chiral benzofuran-fused 1,4-dihydropyridines with excellent yields,wide substrate scope and up to 99% ee.Additionally, this formal [4+2]cycloaddition can be performed in gram scale without noticeable loss of yield and enantioselectivity.     

微波辅助溶胶-凝胶法合成MgO纳米粒子及其催化合成Hantzsch1,4-二氢吡啶性能(英文)

A microwave-assisted sol-gel method was employed for the preparetion of nano-sized MgO particles using Mg(NO 3)2·6H2O as precursor and deionized water as solvent.The sample calcined at 500℃ had a high specific surface area of 243.2m2/g and particles sizes from 9.5to10.5nm.For comparison,MgO nanoparticles were also synthesized without microwave irradiation.X-ray diffraction (XRD) characterization showed the formation of smaller particles after microwave irradiation.The structure and morphology of the MgO particles were analyzed by N2 adsorption-desorption,XRD,scanning electron microscopy,and transmission electron microscopy.Their catalytic behavior was studied with the one-pot synthesis of Hantzsch1,4-dihydropyridines from the reaction of aromatic aldehydes,ethyl acetoacetate,and ammonium acetate.The MgO nanoparticles have high catalytic activity and gave the desired products in good to high yields.The catalyst can be easily recovered by filtration and was used at least three times with only a slight reduction in its catalytic activity.     

Enhancement of Raman Scattering of 1,4-Benzenedithiol by CdS Nanoparticles Assembled on a Silver Surface

CAS nanoparticles were assembled on the smooth surface of a piece of silver by using 1,4-benzenedithiol as coupling molecules. The SEM and resonance Raman spectroscopic characterizations demonstrate that the nanosized structure of CdS was still preserved upon assembly, and a two-dimensional structure of CdS nanoparticles was formed on the substrate surface. The FT-Raman spectra indicate that 1,4-benzenedithiol was coupled between CAS nanoparticles and the silver surface with a tilted orientation. The Raman scattering of 1,4-benzenedithiol was substantially enhanced by the assembled CdS nanoparticles, probably due to the alteration of the polarizability of 1,4-benzenedithiol and the electromagnetic interaction between the dipoles of the CdS particle with its image in the metal substrate.     

Synthesis of novel unsymmetrical coumarinyl-1,4-dihydropyridines

The novel unsymmetrical 3,5-dialkoxycarbonyl-2,6-dimethyl-4-(7′,8′-dimethoxycoumarin-4′-yl)-1,4-dihydropyridines and 5-acetyl-3-alkoxycarbonyl-2,6-dimethyl-4-(7′,8′-dimethoxycoumarin-4′-yl)-1,4-dihydropyridines (coumarinyl-1,4-dihydropyridines) have been synthesized by Knoevenagel condensation of 4-formyl-7,8-dimethoxycoumarin with alkyl acetoacetates in the presence of AlCl₃ followed by cyclization of the resulted Knoevenagel product with other alkyl acetoacetate or acetyl acetone and ammonium acetate. The structure of the intermediate Knoevenagel product and the cyclized unsymmetrical coumarinyl-1,4-dihydropyridines has been established on the basis of their spectral data analysis and single-crystal X-ray diffraction analysis. The observed conformation of the coumarinyl-1,4-dihydropyridines holds the key to promising calcium antagonistic activity of the synthesized coumarinyl-1,4-dihydropyridines.     

Microwave-assisted combinatorial synthesis of hexa-substituted 1,4-dihydropyridines scaffolds using one-pot two-step multicomponent reaction followed by a S-alkylation

A sequential one-pot two-step protocol for microwave-assisted synthesis of Hantzsch-type hexa-substituted 1,4-dihydropyridines has been developed. The three-component reactions of beta-aroylthioamides with aldehydes and acetonitrile derivatives produce the intermediates in situ followed by a S-alkylation to afford hexa-substituted 1,4-dihydropyridines. The reaction presumably proceeds via a Knoevenagel condensation-Michael addition-cyclocondensation-rearrangement-S N2 reaction sequence. Target compounds were obtained in high yields and simply purified by recrystallization. The novel method is complementary to the classical Hantzsch synthesis in that it is well-suited to the preparation of hexa-substituted 1,4-dihydropyridines.     

The First Functionalized 6,12-Diazatetrakishomocubanes

The photodimerization of asymmetric 4-aryl-1,4-dihydropyridines results, totally unexpectedly, in the new 6,12-diazatetrakishomocubanes 1. This is in contrast to the previously observed [2+2] photocycloaddition reactions of symmetrical 4-aryl-1,4-dihydropyridines     

Substitution reactions involving the 2,6-methyl groups of 1,4-dihydropyridines

4,4-Disubstituted 1,4-dihydropyridines (I) are brominated with bromine in chloroform to give 2,6-bis(bromomethyl)-4,4-disubstituted 1,4-dihydropyridines (II), whereas 2,6-bis(dibromomethyl)-4,4-disubstituted 1,4-dihydropyridines (III) are obtained in the case of bromination of I in acetic acid. The bromine atoms in II and III are labile and readily undergo nucleophilic substitution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1519–1524, November, 1978.     

Hydride abstraction in positive-ion electrospray interface: oxidation of 1,4-dihydropyridines in electrospray ionization mass spectrometry

During the positive-ion mode electrospray ionization mass spectrometry analysis of 1,4-diphenyl-3-benzoyl-1,4-dihydropyridines with methanol as the solvent, the major ion generated is one mass unit lower than the analyte, which can be rationalized as the oxidative aromatization of 1,4-dihydropyridines to pyridine cations.     

Highly regioselective photodimerization of 1,4-dihydropyridines: An efficient synthesis of novel 3,6-diazatetraasteranes

Conventional photocycloaddition of 1,4-dihydropyridines does not afford novel head-to-head 3,6-diazatetraasteranes. Herein, we describe a highly regioselective method to synthesize 3,6-diazatetraasteranes via an intramolecular photodimerization of 1,4-dihydropyridines. First, the 1,4-dihydropyridines were tethered by phthaloyl to direct a proximate parallel arrangement in head-to-head orientation by the rotation of CC single bonds in solution. An intramolecular [2 + 2] photocycloaddition proceeded subsequently to give desired 3,6-diazatetraasteranes in high yield (92–97%) and excellent regioselectivity. Furthermore, two different 1,4-dihydropyridines can also be regiocontrolled by this strategy and produce polysubstituted 3,6-diazatetraasteranes via a cross-photodimerization in a concise and efficient way. In addition, this approach can provide direct access to other polysubstituted polyhedron scaffolds from 1,4-dihydropyridine analogues.     

CARO'S ACID SUPPORTED ON SILICA GEL. PART 7: A VERSATILE REAGENT FOR THE AROMATIZATION OF HANTZSCH 1,4-DIHYROPYRIDINES UNDER NON-AQUEOUS CONDITION AND MICROWAVE IRRADIATION

Efficient oxidation of 1,4-dihydropyridines with Caro's acid on silica gel is achieved under nonaqueous conditions and in a domestic microwave oven. The reactions under microwave irradiation were shorter in duration and higher in yields than the reactions in conventional method, confirming the potentiality of microwave heating in aromatization of Hantzsch 1,4-dihydropyridines.     

Sequential three-component reactions: synthesis, regioselectivity and application of functionalized dihydropyridines (DHPs) for the creation of fused naphthyridines

Facile and efficient synthesis of tetrasubstituted 1,4- and 1,6-dihydropyridines (DHPs) has been achieved by employing three-component domino reaction using dimethyl acetylenedicarboxylate (DMAD), aliphatic amines, and α,β-unsaturated aldehyde in the presence of 30 mol % trifluoroacetic acid. Interestingly, regioselectivity for the synthesis of 1,4-dihydropyridines can be increased by using 30 mol % triflic acid. In addition, the synthesis of fused-naphthyridine derivatives has been accomplished involving imino-Diels-Alder reaction by employing 1,4-dihydropyridines, aromatic aldehydes, and aromatic amines.     

Some substitution and heterocyclization reactions based on 1,4-dihydropyridines

Data on the bromination, chlorination, and bromolactonization of 4-aryl-1,4-dihydropyridines are correlated. The reactions of the products of bromination of 4-aryl-1,4-dihydropyridines with various nucleophilic agents (amines and iodide, azide, and thiocyanate ions) and reactions involving the heterocyclization of the products of substitution of the 2,6-methyl groups of 4-aryl-1,4-dihydropyridines, which lead to condensed furo-, difuro-, pyrrolo-, dipyrrolo-, furopyrrolo-, and furothiazolopyridines and thiazolopyridothiadiazines are examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 781–791, June, 1992.     

Bromination of 4-aryl-3,5-dialkoxycarbonyl-2,6-dimethyl-1,4-dihydropyridines

4-Aryl-3,5-dialkoxycarbonyl-2,6-dimethyl-1,4-dihydropyridines are brominated by N-bromosuccinimide in methanol at room temperature at the methyl groups at positions 2 and 6 to form mono-, di-, tri-, and tetrabromo derivatives. When the N-unsubstituted bromomethyl-1,4-dihydropyridines are heated they are easily converted to tetrahydrofuropyridines, but in the case of the analogous N-substituted-1,4-dihydropyridines cyclization does not occur. The 2,6-bis(bromomethyl)-substituted products easily replace bromine under the influence of nucleophilic reagents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1230–1235, September, 1991.