Bis(pyridine)enaminone as a Precursor for the Synthesis of Bis(azoles) and Bis(azine) Utilizing Recent Economic Green Chemistry Technology: The Q-Tube System

We reported herein efficient economic high-pressure synthesis procedures for the synthesis of bis(azoles) and bis(azines) by utilizing the bis(enaminone) intermediate. Bis(enaminone) reacted with hydrazine hydrate, hydroxylamine hydrochloride, guanidine hydrochloride, urea, thiourea, and malononitrile to form the desired bis azines and bis azoles. A combination of elemental analyses and spectral data was used to confirm the structures of the products. Compared with conventional heating, the high-pressure Q-Tube method promotes reactions in a short period of time and provides high yields.

Polymeric Copper(II) Complexes with a Newly Synthesized Biphenyldicarboxylic Acid Schiff Base Ligand—Synthesis, Structural and Thermal Characterization

The newly synthesized biphenyldicarboxylic acid Schiff base and its complexes with Cu(II) were synthesized, and their spectroscopic and structural analysis was performed. The reaction of the ligand and copper(II) acetate in different solvents resulted in the formation of two solvatomorphic complexes, one with MeOH, and the other with DMF molecules, in the crystal lattice. The differences in the results of the thermal analysis could be explained by the different polarities of the solvents present. SC-XRD analysis revealed that the ligand is coordinated as a dianion, in a pentadentate manner, through two phenoxide oxygen atoms, two azomethine nitrogen atoms, and with the oxygen atom of one carboxylate functioning as a bridge that connects the monomeric units. The coordination polyhedron was described with several parameters obtained from different methods of calculation. The presence of different solvents in the crystal structure results in differences in the H-bond networks, and an overall different crystal packing of the structural units in the obtained complexes.

Competitive ways for three-component cyclization of polyfluoroalkyl-3-oxo esters, methyl ketones and amino alcohols

The competitive routes were found for three-component cyclization of polyfluoroalkyl-3-oxo esters, methyl ketones with 3-amino alcohols. It was shown that the reactions with 3-aminopropanol in 1,4-dioxane predominantly lead to hexahydropyrido[2,1-b][1,3]oxazin-6-ones, and in ethanol to 3-hydroxypropylaminocyclohexenones. In contrast, cyclizations with 2-aminoethanol and its analogues, regardless of the reaction conditions, yield hexahydrooxazolo[3,2-a]pyridin-5-ones as the main products. The trans- and cis-diastereomeric structure of heterocycles was established using X-ray and 1H, 19F, 13C NMR spectroscopy, 2D 1H-13C HSQC and HMBC experiments. The mechanism is proposed for competitive transformations of polyfluoroalkyl-3-oxo esters, methyl ketones with 3-amino alcohols.

Synthesis of novel polycarbonyl Schiff bases by ring-opening reaction of ethyl 5-acyl-4-pyrone-2-carboxylates with primary mono- and diamines

An approach for the introduction of the tricarbonyl moiety into aromatic, heterocyclic, and aliphatic amines with the use of acylpyrones has been developed for the synthesis and the design of novel polycarbonyl Schiff base ligands, including salphen structures. This Michael addition-ring-opening reaction proceeds under mild conditions (stirring at 0-20 °C) via the attack at the C-6 position of the pyrone ring in good to high yields (up to 99%) with excellent selectivity. The products can be easily isolated by crystallization without the use of chromatography. The scope of the reaction, tautomeric equilibrium of open-chain products, and their cyclization into pyridone structures were investigated.

A chemo- and regiocontrolled approach to bipyrazoles and pyridones via the reaction of ethyl 5-acyl-4-pyrone-2-carboxylates with hydrazines

Chemo- and regiocontrolled syntheses of pyrazoles and pyridones are presented on the basis of 4-pyrones. A novel approach towards highly functionalized 3,4'-bipyrazoles has been developed by using reactions of ethyl 5-acylcomanoates with hydrazines. The acid-promoted double cyclocondensation allows switching of the structure of the pyrazole rings easily through changing both the nature of hydrazine and the reaction conditions. The transformation of 4-pyrones with phenylhydrazine in EtOH at -20 °C leads to hydroxypyridones as monoaddition products which can be used as precursors for the preparation of pyridone and pyrazole derivatives. A novel rearrangement of 2-hydroxypyridone to pyrazolyl-1,3-diketones in DMSO was found. The structure and regiochemistry of bipyrazoles were confirmed by X-ray analysis and 2D NMR experiments.

Polyfluoroalkylated 2-ethoxymethylene- 3-oxo esters: synthesis and chemical properties overview

The review focuses on the synthesis and chemical properties of polyfluoroalkylated 2-ethoxymethylene-3-oxo esters. The scope and peculiarities of their use as organic reagents in reactions with various N-, C-, O-, mono- and dinucleophiles are discussed in detail. The high reactivity of such derivatives is employed in the construction of enaminoketone, arene and heterocycle frameworks. Particular attention is paid to applications of these building blocks as chemicals for fine organic synthesis, bioactive compounds and metal complexes synthesis.

CaCl2, Bisoxazoline, and Malonate: A Protocol for an Asymmetric Michael Reaction

A mild protocol for the asymmetric Michael addition of dimethyl malonate to various α,β-unsaturated carbonyl compounds was developed. The salient feature of this methodology is that a cheap and environmentally friendly Lewis acid, CaCl2, was used as a catalyst. An aminoindanol- and pyridine-derived ligand provided in the presence of CaCl2 Michael adducts in moderate to high enantioselectivities. The scope of the reaction was demonstrated.

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles

The interaction of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole is an efficient synthetic approach to novel azaheterocycles. 2-Ethoxymethylidene-3-oxo esters bearing alkyl substituents react with 5-aminotetrazole to form ethyl 2-azido-4-alkylpyrimidine-5-carboxylates which are capable of subsequent nucleophilic substitution. The use of diethyl 2-ethoxymethylidenemalonate in this reaction resulted in ethyl 7-hydroxytetrazolo[1,5-a]pyrimidine-6-carboxylate, while ethyl 2-ethoxymethylidenecyanoacetate yielded 5-[2,6-diamino-3,5-bis(ethoxycarbonyl)pyridinium-1-yl]tetrazol-1-ide through an alternative pathway. Ethyl 2-benzoyl-3-ethoxyprop-2-enoate reacted with 5-aminotetrazole by two reaction routes to form ethyl 2-benzoyl-3-(1H-tetrazol-5-ylamino)prop-2-enoate and ethyl 7-(1-ethoxy-1,3-dioxo-3-phenylpropan-2-yl)-5-phenyl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate.

Aza-Knoevenagel-type condensation of secondary amides: direct access to N-monosubstituted β,β-difunctionalized enamines

An efficient approach toN-monosubstituted β,β-difunctionalized enamines, a class of versatile building blocks for the synthesis of bioactive compounds, is reported.