N-Acylbenzotriazole as Proficient Substrate for an Easy Access of Urea, Acyl urea, Carbamates and Thiocarbamates via Curtius Rearrangement Using DPPA as Azide Donor

A diverse range of urea, N-acyl urea, and thiocarbamates has been synthesized in good to excellent yields by reacting N-acylbenzotriazoles individually with amines or amides or thiols or phenols in presence of diphenylphosphorylazide (DPPA) as a suitable azide donor in anhydrous toluene at 110 oC for 3-4 hours. In this route, DPPA is found to be a well alternative of trimethylsilylazide and NaN3 for the azide donor in Curtius degradation. The high reaction yields, one-pot and metal-free condition, straight-forward nature, easy to handling, use of readily available reagents, and in many cases avoid of the column chromatography are the notable features of the devised protocol.

Hydrophobization of cotton fabric with silanes with different substituents

In this paper hydrophobization of cotton fabric with a range of silanes, differing in number of chlorine atoms and in other substituents, was explored. The fabric modification was carried out in silane solutions in anhydrous toluene and in n-hexane. Water contact angles were measured to characterize hydrophili/phobicity of the modified fabrics. Surfaces of the fibers were analyzed using SEM, EDS and ATR-FTIR. Treatment with dichlorodimethylsilane, dichloro(methyl)phenylsilane, 3-chloropropylmethyldichlorosilane and (3,3,3-trifluoropropyl)dichloromethylsilane resulted in hydrophobization, whereas trimethylchlorosilane and 3-aminopropyl(diethoxy)methylsilane were inefficient. Mechanisms of coating with the silanes were proposed. Dielectric spectroscopy of the modified fabric demonstrated that resistance was sensitive to efficiency of reactions removing water from the cotton fibers. Graphic abstract

Synthesis, Characterization, Antimicrobial Screening of 5-Bromobenzofuranyl Aryl Ureas and Carbamates

Present work reports the biologically important benzofuran aryl ureas and carbamates. The benzofuran ring was formed by reacting bromo salicylaldehyde with diethyl bromomalonate in presence of dry acetone and anhydrous potassium carbonate to obtain 5-bromo-2-ethyl carboxylate (1). The obtained ester (1) was converted into corresponding hydrazide (2) by treating with hydrazine hydrate in ethanol. Compound 2 was then converted into 5-bromobenzofuran-2-carbonyl azide (3) by treating it with sodium nitrite in dioxane and acetic acid. The compound 3 is converted into 5-bromobenzofuranyl aryl ureas (4a-e) after treating primary amines and anhydrous toluene. 5-Bromobenzofuranyl aryl carbamate (5) and ethyl carbamate (6) were also synthesized by treating compound 3 with substituted phenol in toluene and ethanol respectively. All the compounds were characterized by NMR, IR and screened for antimicrobial activities.

RATIONAL DESIGN, SYNTHESIS AND CHARACTERIZATION OF HYBRID MOLECULES WITH PYRAZOLINE, PYRIMIDINE AND THIAZOLIDINE NUCLEI AS POTENTIAL ANTIBACTERIAL AGENTS

In this paper, a set of computational tools were used to design and evaluate molecular structures resulting from the combination of the biologically interesting pyrazoline, aminopyrimidine and thiazolidine nuclei (molecular modification) to obtain new bioactive compounds. Key physicochemical properties were calculated (absorption, distribution, metabolism, excretion and toxicity), to determine the bioavailability of the designed compounds and to perform a preselection of 12 derivatives which were then optimized and studied by molecular docking with the receptor PBP3 (4bjp) from Escherichia coli. By these studies, 8 compounds were selected by their binding energies (from -5,36KJ/mol to – 7,05KJ/mol) and significant interactions with the amino acids of the receptor in its active site. In general, the synthesis of the selected compounds was carried out from the α,β-unsaturated carbonyl compounds as precursors. The dihydropyrazole derivatives were obtained from the reaction of chalcones with one equivalent of hydrazine derivatives by one-step cyclocondensations. The pyrimidine series were synthesized starting by the reaction of chalcones and guanidine, giving rise to the corresponding amonopyrimidines, which were then reacted with aromatic and heteroaromatic aldehydes to obtain the acyclic azomethine compounds. The thiazolidine-4-ones were obtained from the aminopyrimidines synthesized above, using three-component cyclocondensation reactions with 2-mercaptoacetic acid and benzaldehyde, in anhydrous toluene or benzene as solvents and using conditions of reflux with Dean- Stark. Finally, assays were carried out aiming to the formation of β-lactam rings, using the Staudinger-type cycloaddition reaction of 2-chloroacetyl chloride with cyclic imines. All the obtained compounds were fully characterized by IR spectroscopy, as well as mono- and bidimensional NMR techniques. The most promising compounds will be evaluated by in vitro assays as potential antibacterial agents.

Synthesis and X-ray diffraction data of 4-benzyloxy-1-oxaspiro-[4.6]-undec-3-en-2-one

The 4-benzyloxy-1-oxaspiro-[4.6]-undec-3-en-2-one (C17H20O3) was prepared through a domino reaction from benzyl α-hydroxycycloheptanecarboxylate and the cumulated ylide Ph3P=C=C=O by: (i) addition and (ii) intramolecular Wittig Olefination reaction. The reaction was carried out using anhydrous toluene as solvent under an argon atmosphere in a Schlenk flask. Molecular characterization was performed by Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, (1H,13C – mono and bidimensional) nuclear magnetic resonance spectroscopy; crystallographic characterization was completed by X-ray diffraction of polycrystalline samples (XRPD). The title compound crystallized in a monoclinical system and unit-cell parameters are reported [a = 13.207(3) Å, b = 5.972(1) Å, c = 19.719(4) Å, β = 105.67(2)°, unit-cell volume V = 1497.5 (4) Å3, Z = 4]. All of the measured lines were indexed with the P21/n (No. 14) space group.

Synthesis and keto-enol tautomerism of ethyl 4-oxo-3,4-dihydro-1H-pyrano[3,4-b]quinoline-3-carboxylate

An efficient method has been developed for the synthesis of a novel β-keto ester-containing pyranoquinoline compound, i.e., ethyl 4-oxo-3,4-dihydro-1H-pyrano[3,4-b]quinoline-3-carboxylate. The method entails a two-step synthesis. The first step involves the Williamson-type reaction of ethyl 2-bromomethyl-3-quinoline-3-carboxylate with ethyl hydroxyacetate in anhydrous benzene to afford the intermediate ethyl 2-[(2-ethoxy-2-oxoethoxy)methyl]quinoline-3-carboxylate. The second step includes the Dieckmann condensation reaction of the resulting intermediate in the presence of sodium ethoxide in anhydrous toluene to afford the desired pyranoquinoline containing β-keto ester moiety. Keto-enol tautomerism of the compound thus obtained was investigated by spectroscopic methods.