Mechanochemical assembly of hydrogen bonded organic-organometallic solid compounds

Solvent-free reactions with molecular systems have been exploited to prepare hybrid organic-organometallic solids: grinding of the complex [Fe(eta 5-C5H4COOH)2] with solid bases B generates quantitatively the corresponding hydrogen bonded salts [Fe(eta 5-C5H4COOH)(eta 5-C5H4COO)][HB] (B = 1,4-diazabicyclo[2.2.2]octane, 1,4-phenylenediamine); gas-solid reactions are also possible with volatile 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 .     

Synthesis of Schiff's bases in aqueous medium: a green alternative approach with effective mass yield and high reaction rates

Abstract

Schiff's bases constitute a class of pharmaceutical and medicinally important molecules. The conventional methods for the synthesis of Schiff's bases require long reaction times and use of organic solvents. We report a novel and eco-friendly condensation reaction method permitting the “green synthesis” of various Schiff's bases by stirring 1,2-diaminobenzene with various aromatic aldehydes in water as solvent. This method is experimentally simple, clean, high yielding, green, and with reduced reaction times. The product is purified by simple filtration followed by washing with water and drying processes.     

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.     

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.     

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.     

Mono-and bis(5-<Emphasis Type="Italic">O</Emphasis>-nitro-1,4:3,6-dianhydro-<Emphasis Type="SmallCaps">D</Emphasis>-sorbit-2-yl) phosphates: synthesis and reactions with hydroxy-and amino-containing compounds

The reaction of 1,4:3,6-dianhydro-D-sorbitol 5-nitrate with POCl₃ afforded mono-and bis(5-O-nitro-1,4:3,6-dianhydro-D-sorbit-2-yl) phosphorochloridates, whose hydrolysis resulted in phosphoric acid mono-and diesters. The subsequent treatment of these compounds with bases gave sodium and cyclohexylammonium salts. The reactions of phosphorochloridates with phenol, pentaerythritol dibromohydrin, and ethylenimine in the presence of organic bases afford mixed phosphates and phosphoramidates. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2026–2032, October, 2007.     

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.     

A novel synthetic method to phenyl-capped penta- and hexaaniline

A new convenient method is reported for the synthesis of the phenyl-capped pentamer and hexamer of aniline. The method was accomplished by the reaction of the parent aniline tetramer in the pernigraniline oxidation state with diphenylamine and N-phenyl-1,4-phenylenediamine in the leucoemeraldine oxidation state, respectively. The mechanism probably involves the formation of cation radicals and their coupling.     

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.     

Nickel-katalysierte Synthese von α-Nornicotin-Derivaten. Vorläufige Mitteilung

Nickel-catalysed Synthesis of α-Nornicotines Schiff's bases 1 and butadiene generally co-oligomerize on nickel catalysts to yield octatrienyl-substituted amines 2 and octadienyl-substituted imines 3 . Schiff's bases 4 and 5 , on the other hand, react with 1, 3-dienes to give new [3+2]-cycloadducts 6 . In addition to the appropriately functionalized α-nornicotine derivatives some higher oligomers are formed.     

Chemical Reactions of Coumarins and Furocoumarins on Thin-Layer Chromatoplates

Most of the reaction achieved in this work were conducted with coumarin and furocoumarin. The reactions were performed on inert thin-layer chromatoplates under controlled conditions and the products of the reactions were compared as usual with the expected substances on the same chromatogram. The reactions performed were: mineral acid hydrolysis, methylation, acetylation, benzoylation, nitration and Schiff's bases on silica gel chromatoplates.     

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.     

Manganese triacetate oxidation of phenolic schiffs bases: Synthesis of 2-arylbenzoxazoles

A concise synthesis of 2-arylbenzoxazoles, 5a-f , is described that occurs via the oxidative cyclization of Schiff's bases, 1a-f , using relatively benign reagent, manganese triacetate.     

A new route to 2-amino- or 2-hydroxy-3-pyridinecarboxylic acid derivatives

Schiff's bases derived from ketones and t-butylamine ( 1 ) reacted with methyl methoxymethylenemalonate to give 2-hydroxy-3-pyridinecarboxylates. Similarly, treatment of 1 with ethoxymethylenemalononitrile gave 2-amino-3-pyridinecarbonitriles. Compounds 1 on reaction with ethyl 2-cyano-3-ethoxypropenoate afforded 2-amino-3-pyridinecarboxylates.     

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.     

Indium Trichloride Catalyzed Diels–Alder Reaction: Synthesis of Novel 5‐Butyl‐11a‐aryl‐4a,5,11,11a‐tetrahydro‐11bH‐indolo[3,2‐c]quinoline‐1,4‐dione

Hetero Diels–Alder reaction of 3‐butyliminomethyl‐2‐aryl‐1H‐indoles (Schiff's base) 1 with p‐benzoquinone 2 affords six novel 5‐butyl‐11a‐aryl‐4a,5,11,11a‐tetrahydro‐11bH‐indolo[3,2‐c]quinoline‐1,4‐diones 3 in good yields. All the reactions proceeded with complete diastereoselectivity giving only one product in each case, which was characterized on the basis of its elemental analyses and spectral data (IR, ¹H NMR, and Mass).     

Synthesis of new 2‐ferrocenyl‐5‐fluoro‐6‐(4‐substituted‐1‐piperazinyl)‐1H‐benzimidazoles of potential biological interest

New substituted 2‐ferrocenylbenzimidazole derivatives are prepared by the oxidation of corresponding Schiff's bases in situ, generated from corresponding 1,2‐diamino‐4‐fluoro‐5‐(1‐piperazinyl)benzenes and 2‐ferrocenecarboxaldehyde using nitrobenzene.     

Directed Aldol Condensations

The present article describes the discovery of a new procedure for aldol condensations for the preparation of α,β-unsaturated carbonyl compounds

1 G. Wittig, H. Pommer, and W. Stilz, German Patent 1199252 (April 5, 1963), BASF; Chem. Abstr. 63, P 1739c (1965).

. The scope of this process is demonstrated by many examples, including some from the natural products sector; at the same time, however, these examples also mark its limitations. The metalated Schiff's bases may be classified as ambident anions; this also explains acylations on the nitrogen. A comparison of the new directed aldol condensation with the formation of unsaturated carbonyl compounds through olefination via phosphorylids shows that the latter method fails when a ketone is used as the substrate. This is where the described procedure using metalated Schiff's bases proves its value.     

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.