Hantzsch Synthesis Research Articles

Lanthanide and asymmetric catalyzed syntheses of sterically hindered 4-isoxazolyl-1,4-dihydropyridines and 4-isoxazolyl-quinolones

The Ytterbium (III) triflate catalyzed Hantzsch synthesis allows for the preparation of sterically hindered 4-isoxazolyl-1,4-dihydropyridines in moderate to good yields. Asymmetric organocatalysis with (R)-4-Oxo-2,6-bis-(2,4,6-triisopropyl-phenyl)-3,5-dioxa-4l5-phospha-cyclohepta[2,1-a;3,4-a’]dinaphthalen-4-ol (R-TRIP) produces moderate yields of chiral 4-isoxazolyl-quinolones with high enantioselectivity.

2-Hydroxyethylammonium acetate: an efficient and reusable homogeneous catalyst for the synthesis of Hantzsch 1,4-dihydropyridines

2-Hydroxyethylammonium acetate ionic liquid was found to be an excellent catalyst for the one-pot synthesis of 1,4-dihydropyridine derivatives via Hantzsch reaction of ethyl acetoacetate or acetoacetanilide, ammonium acetate, and various aromatic aldehydes. The combinatorial syntheses were achieved for the first time using 2-hydroxyethylammonium acetate ionic liquid as a homogeneous catalyst. The catalyst was active for the Hantzsch reaction in alcohol at reflux. The products were isolated in good yields (78–93 %). The resulting substituted dihydropyridines were characterized and confirmed by1H NMR spectral data. The catalyst offers simple means for recovery and the isolated catalyst was reused for three rounds for the synthesis without significant loss of catalytic activity. For all the other reactions carried out with the recycled catalyst, results were similar to that with the fresh catalyst.

A Convenient and Facile Hantzsch Synthesis of Aryl Imidazo[1,2‐b]Isoxazolyl‐N‐aryl Thiazol Amines

The Hantzsch synthesis of novel aryl imidazo[1,2‐b]isoxazolyl‐N‐aryl thiazol amines 5 analogues were described. Reaction of 3‐aminoisoxazole 1 with substituted phenacyl bromides 2 in dry ethanol afforded the corresponding 6‐methyl‐3‐arylimidazo[1,2‐b]isoxazoles 3 in good yields. Compounds 3 on reaction with chloroacetyl chloride in 1,4‐dioxane furnished the corresponding 2‐chloro‐1‐(6‐methyl‐3‐arylimidazo[1,2‐b]isoxazol‐2‐yl)ethanones 4. Compounds 4 on heating with N‐aryl thioureas in an oil bath underwent cyclization to afford the title compounds viz., imidazo[1,2‐b]isoxazolyl‐N‐aryl thiazol amines 5 in moderate to good yields by Hantzsch synthesis.

On-Line Synthesis and Analysis by Mass Spectrometry

In this laboratory experiment, students learn how to use ESI to accelerate chemical synthesis and to couple it with on-line mass spectrometry for structural analysis. The Hantzsch synthesis of symmetric 1,4-dihydropyridines is a classic example of a one-pot reaction in which multiple intermediates can serve to indicate the progress of the reaction as a function of the electrospray variable parameters. This reaction allows students to gauge the effects of the spray variables while observing the enhanced reaction rate through product analysis in the charged microdroplets. Soft ionization techniques used in conjunction with collision-induced dissociation provide students experience with full scan MS to infer reaction progress and collision-induced fragmentation patterns for structural analysis. The experiment as a whole combines the physical phenomena of electrospray, Hantzsch chemical reactivity, and analytical measurements involving use of an ion trap mass spectrometer.

Lewis acidic mesoporous Fe-TUD-1 as catalysts for synthesis of Hantzsch 1,4-dihydropyridine derivatives

Lewis acidic mesoporous material (TUD-1) containing Fe was investigated as stable and reusable catalyst for the synthesis of Hantzsch 1,4-dihydropyridine (DHP) derivatives. Yields between 76 and 91 % of DHP derivatives were obtained in shorter reaction times of 3 h depending on the nature of substituents in benzaldehyde.

Microwave-Assisted Synthesis of Azines and their Condensed Derivatives

In recent years, numerous reports concerning the synthesis of azines and their fused derivatives under microwave irradiation condition have appeared. The use of microwave heating is a valuable tool for synthetic chemists. Being able to reduce reaction times and to increase product yield, this methodology offers to organic chemists the potential to optimize reaction processes. Additionally, application of microwave irradiation leads to many advantages, like the use of non-corrosive and inexpensive reagents, in addition to the eco-friendly and quot; green chemistry and quot; economical and environmental impacts. In this review, we report the important role of microwave activation and their advantages in the synthesis of medically important azines and their fused derivatives. Keywords: Azines, biginelli synthesis, dihydropyridines, dihydropyrimidinones, green synthesis, hantzsch synthesis, heteroatom, microwave-assisted organic synthesis, microwave-assisted synthesis, microwave irradiation, multi-component reaction, pyridine, pyridine dicarbonitriles, pyrimidine, triazines.

ChemInform Abstract: Graphite Oxide‐Promoted One‐Pot Synthesis and Oxidative Aromatization of Hantzsch 1,4‐Dihydropyridines.

AbstractGraphite oxide is a readily available, inexpensive, mild, and efficient agent for the one‐pot synthesis of pyridine compounds (III) using a three‐component Hantzsch reaction.

Preparation and characterization of mesostructured Zr-SBA-16: efficient Lewis acidic catalyst for Hantzsch reaction

Mesostructured Zr-SBA-16 (3D cubic arrangement, Im3m space group) with different Si/Zr ratio was successfully synthesized by using Pluronic F127 triblock copolymer and n-butanol as a structure directing agent. Successful incorporation of Zr4+ ions was achieved without any pH adjustments up to ~6.5 wt% of Zr loading. Different analytical techniques such as SAXS, N2-physisortion and HR-TEM were used to ascertain the structure of Zr-SBA-16 samples whereas, diffuse reflectance UV–Vis, pyridine adsorbed FTIR and NH3 desorbed TPD methods were assessed to understand the nature of Zr incorporation. The Lewis acidity of Zr-SBA-16 was explored in the synthesis of Hantzsch 1,4-dihydropyridine derivatives via condensation of substituted benzaldehyde, ethyl acetoacetate and ammonium acetate.

L-Tyrosine loaded nanoparticles: an efficient catalyst for the synthesis of dicoumarols and Hantzsch 1,4-dihydropyridines

l-Tyrosine loaded nanoparticles catalyzed organic reactions.

Correction to enantioselective organocatalytic hantzsch synthesis of polyhydroquinolines.

The following changes were made to the revised Supporting Information document submitted with this correction: (1) All data referring to compound 4o has been removed. (2) HPLC traces for 4a, 4d, 4h, and 4n have been replaced with less ambiguous choices, pp 43−47. (3) Clarification of the method to confirm peak identities is now included, p 48. (4) Confirmation of peak identities is now included for compounds 4a, 4d, 4h, 4k, 4l, and 4n, pp 48−50. (5) Missing retention times for compounds 4a and 4g have been added on p 42. (6) H NMR peaks have been added for compounds 4k and 4j. These were missing in the original document, p 5. (7) The new Supplemental Figure 1 has been added (p 2), which shows that the Hantzsch reaction to produce compound 4b does not proceed in the absence of catalyst. We previously neglected to include this important data. This material is available free of charge via the Internet at http://pubs.acs.org.

Graphite oxide-promoted one-pot synthesis and oxidative aromatization of Hantzsch 1,4-dihydropyridines

A new and efficient method for the one-pot synthesis of pyridine compounds using three-component Hantzsch synthesis in high yields using graphite oxide, a readily available and inexpensive material, as a mild and efficient agent is described.

Cu-doped ZnO nanocrystalline powder as a catalyst for green and convenient multi-component synthesis of 1,4-dihydropyridine

A simple, efficient, and convenient one-step method for synthesis of Hantzsch 1,4-dihydropyridine, using Cu-doped ZnO nanocrystalline powder as a catalyst is reported. The method offers several advantages including excellent yields, green solvent, easy work-up, simplicity in operation and catalyst reusability.

ChemInform Abstract: An Efficient One‐Pot Synthesis of Aryl‐Substituted 1‐(Thiazol‐2‐yl)‐1H‐pyrazole‐3‐carboxylates via a Hantzsch Synthesis‐Knorr Reaction Sequence.

AbstractA great variety of title compounds is conveniently synthesized by reaction of thiazoles obtained by Hantzsch synthesis with previously prepared enolic lithium salts of diketoesters.

ChemInform Abstract: Facile Synthesis of Hantzsch 1,4‐Dihydropyridines with Unsymmetrical 2,6‐ and 3,5‐Substituents.

AbstractThe presented variation of the classical Hantzsch synthesis constitutes a facile one‐pot two step procedure.

Solvent-free efficient one-pot synthesis of Biginelli and Hantzsch compounds catalyzed by potassium phthalimide as a green and reusable organocatalyst

The usage of potassium phthalimide (PPI) for the simple and green one-step multicomponent synthesis of Hantzsch 1,4-dihydropyridines, polyhydroquinolines, 3,4-dihydropyrimidin-2(1H)-ones/thiones, and octahydroquinazolinones under solventless conditions at 120 °C is reported. The method is operationally simple, environmentally benign, and has relatively high yields. The other merits of this method include efficient, clean, green, and catalyst reusability.

One-pot, multicomponent synthesis of symmetrical Hantzsch 1,4-dihydropyridine derivatives using glycerol as clean and green solvent

Multi component, one pot synthesis of symmetrical 1,4-dihydropyridine derivatives from the condensation of ethyl/methyl acetoacetate, aromatic/aliphatic aldehyde and ammonium acetate has been described using glycerol, as economical, easily available and environmentally benign reagent. The targeted molecules were obtained in high purity and excellent yield without use of any additional catalyst and methodology from readily available starting materials.

Solvent-Free Synthesis of Dihydropyridines and Acridinediones via a Salicylic Acid–Catalyzed Hantzsch Multicomponent Reaction

A multicomponent Hantzsch synthesis of 1,4-dihydropyridines and acridinediones from commercially available aldehydes, ammonium acetate, and ethyl acetoacetate or dimedone, in the presence of salicylic acid as an efficient catalyst, in good yield and short reaction time is reported. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

Sulfonated Carbon/Silica Composites: Highly Efficient Heterogeneous Catalysts for the One-Pot Synthesis of Hantzsch 1,4-dihydropyridines, 2,4,5-trisubstituted Imidazoles and 2-arylbenzimidazoles

Sulfonated Carbon/Silica Composites: Highly Efficient Heterogeneous Catalysts for the One-Pot Synthesis of Hantzsch 1,4-dihydropyridines, 2,4,5-trisubstituted Imidazoles and 2-arylbenzimidazoles

Synthesis and fluorescence properties of benzoxazole-1,4-dihydropyridine dyads achieved by a multicomponent reaction

Photoactive ESIPT dyads with a high Stokes' shift were obtained by a multicomponent one-pot Hantzsch synthesis.

Facile Synthesis of Hantzsch 1,4-Dihydropyridines with Unsymmetrical 2,6-and 3,5-Substituents

A facile synthesis of Hantzsch 1,4-dihydropyridines with unsymmetrical 2,6- and 3,5-substituents in a one-pot two-step tandem reaction under solvent-free conditions, promoted by microwave irradiati...