Synthesis Of Hydrazones Research Articles

Selective Reduction of Azines to Benzyl Hydrazones with Sodium Borohydride Catalyzed by Mesoporous Silica‐Supported Silver Nanoparticles: A Catalytic Route towards Pyrazole Synthesis

AbstractThe catalytic activity of supported silver nanoparticles on mesoporous silica was studied, for the selective reduction of azines into benzyl hydrazones using sodium borohydride as mild reducing agent. Different sizes of silver nanoparticles supported on mesoporous silica (Ag/HMS) were successfully prepared by two methods, i.e., wet impregnation followed by reduction with hydrogen at 350 °C and in situ deposition/reduction with a mixture of amines (ethanolamine and ethylenediamine). The Ag/HMS (amines) catalyst was found to promote the selective 1,2‐reduction of aryl‐substituted azines, compared to the corresponding 1,4‐reduction that occurs in general reduction processes. This catalytic transfer hydrogenation process found to be clean, fast and quantitative (>99% yields and selectivity) towards benzyl hydrazone synthesis under mild conditions. Of great importance is that under the present catalytic conditions reducible functional groups remain intact. Formal kinetics, support the in situ formation of silver hydride species being responsible for the reduction process. The presence of protic polar methanol enhanced the catalytic activity of Ag/HMS. Based on the recycling studies the catalytic system Ag/HMS‐NaBH4 was found to catalyze the selective reduction of azines nine times without significant loss of its activity. Finally, a one‐pot reaction between the in situ produced benzyl hydrazones and a series of nitrostyrenes readily provided the regioselective synthesis of 1,3,5‐subtituted pyrazoles, highlighting a useful synthetic application of the catalytic protocol.magnified image

Synthesis of Hydrazones from Amino Acids and their Antimicrobial and Cytotoxic Activities

Hydrazones 6a–6n were synthesized from different amino acids with various aldehydes under reflux in methanol/ethanol. The structures of synthesized compounds were ascertained by elemental analysis and spectroscopic techniques. A comparative study of the antimicrobial activity and cytotoxicity was carried out of the N‐protected amino acids, their esters, hydrazides, and the respective hydrazones, providing good results in cytotoxicity studies.

Unprecedented cyclization of α-diazo hydrazones upon N-H functionalization: A Et3N base promoted one-step synthetic approach for the synthesis of N-amino-1,2,3-triazole derivatives from α-diazo hydrazone

In this communication, for the first time, we are reporting α-diazo hydrazone synthesis from hydrazones derived from β-keto esters and 2,4-dinitro phenyl hydrazine via diazo transfer reaction. We also report an unexpected cyclization of the α-diazo hydrazones upon N-H functionalization to give highly functionalized N-amino-1,2,3-triazole derivatives under metal-free condition. This one-step synthetic protocol can serve as a general tool to access nitrogen rich 5- and 6-membered heterocycles in excellent yields.

Direct synthesis of hydrazones by visible light mediated aerobic oxidative cleavage of the CC bond

A metal-free protocol through visible light mediated oxidative cleavage of CC bonds to directly construct CN bonds has been developed for the conversion of alkenes to hydrazones under mild conditions.

Simple and efficient approach for synthesis of hydrazones from carbonyl compounds and hydrazides catalyzed by meglumine

ABSTRACTA simple, environmentally benign protocol for synthesis of hydrazones from carbonyl compounds and hydrazides has been developed in the presence of meglumine in aqueous-ethanol media at room temperature. The salient features of the present protocol are mild reaction conditions, short reaction time, high yields, operational simplicity, metal-free, applicability toward large-scale synthesis, and biodegradable and inexpensive catalyst.

An efficient and stereoselective approach to 14-membered hexaaza macrocycles using novel semicarbazone-based amidoalkylation reagents

An efficient synthesis of hydrazones of 4-(3-oxobutyl)semicarbazides and 4-(3-oxobutyl)semicarbazones using novel semicarbazone-based amidoalkylation reagents, 1-arylidene-4-[(aryl)(tosyl)methyl]semicarbazides, has been developed. The synthesis involved reaction of the latter with the Na-enolate of acetylacetone, followed by a base-promoted retro-Claisen reaction and treatment of the obtained 4-(3-oxobutyl)semicarbazones with hydrazine or methylhydrazine. The prepared hydrazones were converted stereoselectively into 14-membered cyclic bis-semicarbazones under acidic conditions. Especially high selectivity (trans/cis⩾97:3) was observed upon the macrocyclization of 4-(3-oxobutyl)semicarbazone hydrazones. A plausible reaction pathway and the stereochemistry of this cyclization were discussed.

ChemInform Abstract: A General Photoinduced Electron Transfer‐Directed Chemoselective Perfluoroalkylation of N,N‐Dialkylhydrazones.

A selective, practical and general incorporation of fluoroalkyl groups into organic frameworks is of great interest for synthesis. Herein we report the first metal-free, initiator-free, and general photochemical perfluoroalkylation of a variety of N,N-dialkylhydrazones at room temperature in the absence of any external photocatalyst. It constitutes an important advance in perfluoroalkyl radical addition to CN π bonds for the synthesis of hydrazones instead of amines. Affordable and easily available perfluoroalkyl iodides serve as effective precursors. The excellent regio-, stereo- and chemoselectivity as well as the broad substrate scope make this a very promising synthetic tool.

Синтез та алкілування аміду, отриманого на основі N-фталоілгліцину та гідразиду ендикової кислоти

Himic acid hydrazide derivatives are promising in terms of practical use compounds due to their wide range of biological effects (primarily neurotropic activity) and their synthetic potential. Earlier investigated in detail the methods of synthesis of hydrazones, urea, amide and imide derivatives of himic acid hydrazide. Also known diverse biological action of N-Phthaloylglycine, which could serve as an effective protection for the amino group of glycine and has interesting structural features that contribute to the formation of supramolecular complexes. The methodology of synthesis of 2-(Phthalimidoyl)-N-benzyl-N-(4-azatricyclo[5.2.1.02-endo,6-endo]dec-8-ene-3,5-dione-4-yl)acetamide, including obtaining of 2-(Phthalimidoyl)-N-(4-azatricyclo[5.2.1.02-endo,6-endo]dec-8-ene-3,5-dione-4-yl)acetamide based on himic acid hydrazide acid and Phthalylglycyl chloride and alkylation of obtained product. Found that acceptable yield is observed during the alkylation reaction in boiling solution of anhydrous acetone in the presence of excess calcined potassium carbonate. The structure of obtained products was confirmed by analyzing the 1H NMR spectrum.

N-(4-芳基噻唑-2-基)-对苄氧基苯乙酮腙的合成

N-(4-芳基噻唑-2-基)-对苄氧基苯乙酮腙的合成

Fe-Catalyzed Olefin Hydroamination with Diazo Compounds for Hydrazone Synthesis.

A novel Fe-catalyzed olefin hydroamination with diazo compounds for accessing hydrazones has been developed. Diazo compounds are used as radical acceptors and can be trapped by the in situ generated alkyl radical toward C-N bond formation. The reaction conditions are mild, and the substrate scope is broad. Additionally, this hydroamination protocol is applicable for intramolecular reactions to construct diverse heterocycles.

Visible‐Light Photoredox‐Catalyzed C−H Difluoroalkylation of Hydrazones through an Aminyl Radical/Polar Mechanism

AbstractAn unprecedented visible‐light‐induced direct C−H bond difluoroalkylation of aldehyde‐derived hydrazones was developed. This reaction represents a new way to synthesize substituted hydrazones. The salient features of this reaction include difluorinated hydrazone synthesis rather than classical amine synthesis, extremely mild reaction conditions, high efficiency, wide substrate scope, ease in further transformations of the products, and one‐pot syntheses. Mechanistic analyses and theoretical calculations indicate that this reaction is enabled by a novel aminyl radical/polar crossover mechanism, with the aminyl radical being oxidized into the corresponding aminyl cation through a single electron transfer (SET) process.

Visible-Light Photoredox-Catalyzed C-H Difluoroalkylation of Hydrazones through an Aminyl Radical/Polar Mechanism.

An unprecedented visible-light-induced direct C-H bond difluoroalkylation of aldehyde-derived hydrazones was developed. This reaction represents a new way to synthesize substituted hydrazones. The salient features of this reaction include difluorinated hydrazone synthesis rather than classical amine synthesis, extremely mild reaction conditions, high efficiency, wide substrate scope, ease in further transformations of the products, and one-pot syntheses. Mechanistic analyses and theoretical calculations indicate that this reaction is enabled by a novel aminyl radical/polar crossover mechanism, with the aminyl radical being oxidized into the corresponding aminyl cation through a single electron transfer (SET) process.

Phosphine-mediated addition of 1,2-dicarbonyls to diazenes: an umpolung approach toward N-acyl hydrazone synthesis

Using a Kukhtin–Ramirez-like condensation employing hexamethylphosphorous triamide, the addition of 1,2-dicarbonyls to diazenes affords direct access to N-acyl hydrazones in moderate to excellent yields. The strategic assembly of this ubiquitous functional group proceeds through an umpolung disconnect in which an in situ generated acyl anion equivalent reacts with an electrophilic azodicarboxylate to form a new C–N bond. The method presented herein complements traditional condensation approaches toward hydrazone synthesis to access important synthetic intermediates and potentially biologically relevant architectures.

Aromatic aldehyde thiosemicarbazones in the synthesis of hydrazones of the pyrimidine series

4-[(Arylmethylidene)hydrazinyl]-6-methylpyrimidin-2-amine hydrochlorides have been synthesized by reaction of N-(4-chloro-6-methylpyrimidin-2-yl)formamide with thiosemicarbazones derived from aromatic aldehydes.

A modification of a conventional technique for the synthesis of hydrazones of racemic carbonyls: prevention of spontaneous chiral inversion

Conventionally hydrazones and other derivatives of carbonyls are synthesized under acidic conditions when spontaneous chiral inversion is a common problem if the carbonyl compound is chiral.

Synthesis of hydrazones of anabasinylacetic acid and structure of its isopropylidenehydrazone

Some hydrazones based on N-anabasinylacetic acid hydrazide have been synthesized. Structure of N′-isopropylidenehydrazone of N-anabasinylacetic acid has been studied by X-ray diffraction.

Reactions of Resin-Bound Triazenes with Dithianylium Tetrafluoroborates: Efficient Synthesis of α-Azo Ketene Dithioacetals and Related Hydrazones

The conversion of dithianylium cations into α-azo ketene dithioacetals via addition of polymer-bound diazonium precursors is shown. This new procedure allows the synthesis of α-azo ketene dithioacetals in one step within 2-90 min at rt and yields highly pure compounds that do not have to be purified in most cases. The α-azo ketene dithioacetals obtained have been shown to be valuable intermediates for the synthesis of hydrazones, α-halogenated α-azo ketene dithioacetals, and azo-functionalized dienes.

Room temperature ionic liquid choline chloride–oxalic acid: A versatile catalyst for acid-catalyzed transformation in organic reactions

An efficient and facile synthesis of hydrazones, bis(indolyl)methanes and bis(4-hydroxycoumarin)methanes is facilitated by room temperature ionic liquid choline chloride–oxalic acid (ChCl:Ox). ChCl:Ox (10mol%) efficiently catalyzes condensation of aldehydes with phenylhydrazine giving corresponding hydrazones in high yield (92–96%) within short reaction time of 3–5min. Electrophilic cyclization reaction of indole and 4-hydroxy coumarin with aromatic aldehyde was effectively promoted by 30mol% of ChCl:Ox giving corresponding bis(indolyl)arylmethanes and bis (4-hydroxycoumarin)methanes in good yield at room temperature. Procedure is very simple, solvent free and completely eliminates use of toxic acid catalyst. ChCl:Ox is biodegradable, can be recycled and reused without the loss of efficiency with respect to yield.

ChemInform Abstract: A Practical Approach to Semicarbazone and Hydrazone Derivatives via Imino‐isocyanates.

Complex hydrazone derivatives can be accessed readily from hydrazones upon heating in the presence of nucleophiles. This reactivity likely involves imino-isocyanate intermediates, and a variety of leaving groups can be used at temperatures ranging from 20 to 150 °C. Alcohols, thiols, primary, and secondary amines can be used as nucleophiles, thus providing a simple alternative to the synthesis of hydrazones via condensation on the parent carbonyl precursor and allowing late-stage derivatization.

A Practical Approach to Semicarbazone and Hydrazone Derivatives via Imino-isocyanates

Complex hydrazone derivatives can be accessed readily from hydrazones upon heating in the presence of nucleophiles. This reactivity likely involves imino-isocyanate intermediates, and a variety of leaving groups can be used at temperatures ranging from 20 to 150 °C. Alcohols, thiols, primary, and secondary amines can be used as nucleophiles, thus providing a simple alternative to the synthesis of hydrazones via condensation on the parent carbonyl precursor and allowing late-stage derivatization.