Green route synthesis of Schiff's bases of isonicotinic acid hydrazide

Abstract

Imines constitute a class of therapeutic agents that possess a broad spectrum of pharmacological activity. The conventional method for synthesis of imines by nucleophilic addition of amines to ketones or aldehydes requires long reaction times along with the use of organic solvents and a glacial acetic acid catalyst. We report the synthesis of Schiff's bases of isonicotinic acid hydrazide by novel, green routes using sonication, stirring, and microwave irradiation, respectively. Initial results are reported and indicate that by employing greener methods under aqueous conditions, high yields and shorter reaction times can be achieved.     

A Facile Synthesis of Novel [4‐(Aryl)‐3a,4,5,9b‐tetrahydrocyclopenta[c]quinolin‐8‐ylmethyl]‐8′‐(4′‐aryl)‐3a′,4′,5′, 9b′‐tetrahydro‐3H‐cyclopenta[c]quinolines: Indium Trichloride Catalyzed Intermolecular Imino Diels–Alder Reaction of Cyclopentadiene with Schiff's Bases

Abstract

A simple and efficient method for the synthesis of the title compounds from Schiff's bases derived from 4,4′‐diaminodiphenylmethane and excess of cyclopentadiene using anhydrous indium trichloride as a catalyst is described.     

Azo compounds and Schiff 's bases derived from 5-(4-pyridyl)-2-amino-1,3,4-thiadiazole: synthesis,mesomorphic properties and structural study by semi-empirical calculations

The synthesis and liquid crystalline properties of new Schiff 's bases (series 3a-f) and azo compounds (4a-f) incorporating pyridine and 1,3,4-thiadiazole rings are reported. The first homologues in the series of Schiff's bases (3a-c) show a monotropic mesophase and the homologues 3d-f display an enantiotropic SmA phase. The only azo compounds to exhibit liquid crystalline properties are the homologues 4e, f which show a monotropic nematic phase. These series are compared with Schiff's bases and azo compounds analogues (series 5 and 6), previously reported by us and an AM1 study of the structure/mesomorphic property relationship is described.     

Novel amides and Schiff's bases derived from 1,3,4-oxadiazole derivatives: synthesis and mesomorphic behaviour

The synthesis and liquid crystalline properties of novel achiral amides (Ia–g, IIa–g and IVa,b), achiral Schiff's bases (IIIa–g and Va–g), chiral amides (VI, VII) and chiral Schiff's bases (VIII–XI) incorporating a 1,3,4-oxadiazole ring are reported. All amides of the series I and II display an enantiotropic smectic A phase. The amide IVa,b did not show mesomorphic properties. Amides of the series Ia–g and IIa–g contain a flexible n-tetradecylthio chain, the other terminal substituent is an n-alkoxy chain and n-alkyl chain, respectively (n?=?4–10) and the 1,3,4-oxadiazole is in the terminal rigid core. Amides Ia–g have broader mesomorphic range and higher thermal stability than the corresponding amides IIa–g. Amides IVa,d contain the 1,3,4-oxadiazole ring in the centre of the rigid core and two flexible alkoxy chains as flexible terminal substituents. Thus, the mesomorphic properties are favoured if 1,3,4-oxadiazole is shifted to a terminal position of the rigid core. Schiff's bases IIIa–g display an enantiotropic dimorphism smectic C–smectic A. Schiff's bases IIIa–g have a broader mesomorphic range than the analogous amides Ia–g. Schiff's bases Va–g exhibit a dimorphism smectic A–nematic, and in contrast to this the analogous amide IVa,b did not show mesomorphism. The chiral amides VI and VII and chiral Schiff's bases X and XI did not show mesomorphic properties and only the chiral Schiff's bases VIII and IX display a chiral smectic C phase in a short mesomorphic range. A density functional theory theoretical study at the B3LYP/6–311++G(d,p) level was performed in order to analyse the structural features that must be related with the mesomorphic behaviour of the reported compounds.     

A 13C NMR study of pyridoxal-5′-phosphate oxime

Pyridoxal-5′-phosphate amino-oxy acetate oxime was titrated in water, over the pH range 4–12, and the changes followed using ¹³C NMR. The results were compared to those of analogous Schiff's bases presented in the literature. The chemical shifts and titration curves of the oxime were appreciably different from those of the Schiff's bases, and the differences are explained as being due to the absence of ketoenamine-enolimine tautomerism in the oxime. The low chemical shift value and the large changes of the oxime azomethine carbon during titration, as compared to the Schiff's bases, are discussed. The high stability of the oximes in water makes them suitable as model compounds for some tautomeric forms of the Iess stable Schiff's bases.     

Retro-ene reactions in heterocyclic synthesis. II. A facile synthetic method for 4-hydroxy-2-pyridones

Schiff's bases 1 derived from ketones and t-butylamine reacted with diphenyl malonate, diphenyl methyl-malonate and diphenyl phenylmalonate to give 4-hydroxy-2-pyridones 4–6 . Schiff's bases b on reaction with trimethyl methanetricarboxylate afforded 4-hydroxy-3-methoxycarbonyl-2-pyridones 12 .     

A Convenient Method of Synthesis of Bis-Indolylmethanes: Indium Trichloride Catalyzed Reactions of Indole with Aldehydes and Schiff's Bases

Anhydrous indium trichloride (InCl₃) is found to catalyze the electrophilic substitution reaction of indole with aromatic aldehydes and Schiff's bases which resulted in an efficient synthesis of bis-indolylmethanes in good to excellent yield.     

Facile synthesis of phenyl-capped oligoanilines using pseudo-high dilution technique

Monodispersed phenyl-capped trianiline and tetraaniline were successfully synthesized by the reactions of diphenylamine with acetaldehyde-based Schiff's bases of N-phenyl-1,4-phenylenediamine and 1,4-phenylenediamine, respectively, in the presence of ammonium persulfate and hydrochloric acid, subsequent deprotonation and reduction with phenylhydrazine. The reaction mechanism probably involves the slow hydrolysis of the Schiff's bases and subsequent oxidative coupling reactions of the formed ammonium salts with diphenylamine at pseudo-high dilution condition of the salts.     

Spectroscopic studies of new Schiff and Schiff–Mannich bases of ortho-derivatives of 4-bromophenol

Three Schiff's bases and two Schiff–Mannich bases derivatives of 4-bromophenol were synthesised and studied by FT-IR and ¹H, ¹³C, ¹⁵N NMR and CPMAS spectroscopy. For comparison the Schiff's base of 5-bromo-2-methoxy-benzaldehyde with pentafluoroaniline was also studied. The structures of Schiff's bases and the hydrogen bonds within these structures are discussed.     

Synthesis of Substituted 1,4‐Dihydropyridines in Water Using Phase‐Transfer Catalyst Under Microwave Irradiation

Abstract

The synthesis of various substituted 1,4‐dihydropyridines has been achieved by the reaction of aldehydes, ethyl/methyl acetoacetates, and ammonium acetate in water using phase‐transfer catalyst under microwave irradiation. Compared to the classical Hantzsch's reaction conditions, this new method consistently has the advantage of good yields and short reaction times. Bifunctional compounds containing two units have been synthesized using dialdehyde as precursor in good yields.     

Ring-opening oligomerization reactions using aluminium complexes of schiff's bases as initiators

Bifunctional telechelics with defined structure can be prepared by oligomerization of oxiranes, β-butyrolactone and L-lactide using aluminium Schiff's base complexes as initiators. Chiral initiator (SALCENAlCl) shows a stereoelective character leading to preferential oligomerization of one enantiomer from a racemic monomer mixture. The reaction with β-butyrolactone proceeds through O-alkyl cleavage. Alkoxy Schiff's bases aluminium complexes are used for oligomerization of L-lactide. All the prepared oligomers were fully characterized by IR, elemental analysis, ¹H and ¹³C NMR and GPC.     

Green and Catalyst-Free One-Pot Synthesis of Anthranilamide Schiff Bases: An Approach Toward Sirtinol

A novel and simple method for the green one-pot synthesis of anthranilamide Schiff bases is described. The reported Schiff bases are obtained via the reaction of isatoic anhydride, amines, and aromatic aldehydes in water at room temperature, without using any catalysts. No cyclization toward 2,3-dihydro-4(1H)-quinazolinones occurred in this method and anthranilamide Schiff bases were produced exclusively. This approach offers a green method to prepare the medicinally important Schiff base sirtinol and other bioactive anthranilamide Schiff bases.

[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.]     

Green route synthesis of 4-thiazolidinone analogs of isonicotinic acid hydrazide

Abstract

The broad and potent activity of 4-thiazolidinones has established it as one of the biologically important scaffolds. The synthesis of N-(2-aryl-4-oxothiazolidin-3-yl)isonicotinamide by a novel method of stirring and sonication is described. The conventional method for synthesis of 4-thiazolidinones involves use of a Dean-Stark water separator for the removal of water from the reaction with long reaction times (12–48 h), and the stirring procedure also involves the use of DCC (dicyclohexylcarbodiimide) as a dehydrating agent. We report the synthesis of 4-thiazolidinone analogs of isonicotinic acid hydrazide by novel, green route methods of sonication and stirring using molecular sieves. Results indicate that high yields and shorter reaction times can be achieved by employing novel green route methods of synthesis.     

Tween-20: An Efficient Catalyst for One-Pot Synthesis of α-Aminophosphonates in Aqueous Media

Abstract

A green one-pot three-component synthesis has been developed for α-aminophosphonates by condensation of aldehydes, amines, and diethylphosphite by using nonionic surfactant Tween-20 as catalyst in aqueous media. The results showed that this synthetic route for α-aminophosphonates takes just 25–60 min for completion at 60 °C and affords 64%–91% yields depending on the nature of the amine substrates. The major advantages of this novel method are green reaction conditions with water as solvent, simple workup, less reaction times, and high to moderate yields.     

A novel approach toward thioester bond formation mediated by N,N’ -diisopropylcarbodiimide in water

Abstract

A simple and efficient method has been developed for the synthesis of thioesters from carboxylic acids and thiols using N,N'-diisopropylcarbodiimide (DIC). The reactions were carried out in water as an environmentally friendly and green solvent. The developed procedure presents an economic, efficient, mild, and very simple protocol for thioesterification reaction in aqueous media.     

Convenient synthesis of 1,2,3,4‐tetrahydro‐pyrimidin‐5‐ylbenzoxazoles

2‐Pyrimidin‐5‐ylbenzoxazoles 7 have been synthesized by condensation of 5‐pyrimidinecarboxaldehyde 4 with substituted aminophenols 5 followed by oxidative cyclization of the resulting Schiff's bases 6 with iodobenzene diacetate. Subsequent formation of methylpyrimidinium salts 8 and reduction thereafter afforded tetrahydropyrimidinylbenzoxazoles 10. This method has been utilized in the synthesis of M₁ muscarinic agonist candidates.     

Molecular Design of Calixarene 5. Syntheses and Cation Selectivities of Novel Schiff's Base p‐tert‐Butylcalix[4]arenes

Five novel Schiff's bases p‐tert‐butylcalix[4]arenes have been synthesized in high yields by the reaction of 1,3‐distally disubstituted p‐tert‐butylcalix[4]arene amine (1) with the corresponding aromatic aldehydes, and their cation binding abilities and selectivities with alkali and heavy metal ions have been evaluated by solvent extraction of aqueous metal picrates to show the highest Ag⁺ extractability for Schiff's base p‐tert‐butylcalix[4]arene (6) and the best Na⁺/Li⁺ and Ag⁺/Ti⁺ selectivities for Schiff's base p‐tert‐butylcalix[4]arene (4 and 2) over any other calix[4]arene derivatives, respectively.     

Green Synthesis of 1‐(1,2,4‐Triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)indole]‐2′,4′(1′H)‐diones as Potential Insecticidal Agents

One pot green synthesis of 1‐(1,2,4‐triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)‐indole]‐2′,4′(1′H)‐diones was carried out by the reaction of indole‐2,3‐diones,4‐amino‐4H‐1,2,4‐triazole and acetyl chloride/chloroacetyl chloride in ionic liquid [bmim]PF₆ with/without using a catalyst. It was also prepared by conventional method via Schiff's bases, 3‐[4H‐1,2,4‐triazol‐4‐yl]imino‐indol‐2‐one. Further, the corresponding phenoxy derivatives were obtained by the reaction of chloro group attached to azetidine ring with phenols. The synthesized compounds were characterized by analytical and spectral (IR, ¹H NMR, ¹³C NMR, and FAB mass) data. Evaluation for insecticidal activity against Periplaneta americana exhibited promising results.     

Synthesis,mesomorphic properties and structural study by semi-empirical calculations of amides containing the 1,3,4-thiadiazole unit

The synthesis and liquid crystalline properties of a new series of amides (series 2a-f,3a-d and 4a-d) incorporating pyridine and 1,3,4-thiadiazole rings are reported. No homologues of the series 2 show mesomorphic properties. In the series 3 only the highest homologues (3d) displays an enantiotropic SmA mesophase; the compound 3c exhibits a monotropic SmA mesophase, and the homologues 3a,b display no liquid crystal properties. The amides 4b-d display an enantiotropic SmA phases and the first homologue (4a) exhibit only crystalisotropic transition. These series are compared with previously reported Schiff's bases and amide analogues. A structural study by AM1 semi-empirical calculation is also described.     

Anil-Synthese 22. Mitteilung über die Herstellung von Styryl-und Distyryl-Derivaten des Pyridins

Preparation of Styryl and Distyryl Derivatives of Pyridine 2,4-, 2,5- and 2,6-Dimethylpyridines react with anils of aromatic aldehydes in the presence of dimethylformamide and potassium hydroxide to yield the corresponding distyrylpyridines (‘anil synthesis’). Under the same reaction conditions (4-methylstyryl)pyridines are converted to (stilbenylvinyl)pyridines. Similarly, the Schiff's base derived from pyridine-3-carbaldehyde and p-chloroaniline on treatment with methyl- and p-tolyl-substituted aromatic heterocycles gives the corresponding (heteroaryl-styryl)pyridines, whereas with the Schiff's bases derived from pyridine-2- and -4-carbaldehyde side reactions, such as dimerization followed by disproportionation predominate.