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Cyclization Reactions Involving 2-Aminoarenetellurols and Derivatives of α,β-Unsaturated Carboxylic Acids
The reductive cyclization of arenetellurols carrying α,β-unsaturated amide functionalities in the ortho position was investigated. Conceptually, such compounds can form 1,3-tellurazoles without the involvement of the unsaturation in the ring closure, they can form 1,4-tellurazinone derivatives, or they can undergo ring closure to 1,5-tellurazepinones. Amides derived from acrylic and methacrylic acid generated 1,5-tellurazepinones while 2-cinnamylamidobenzenetellurol cyclized to a 1,3-tellurazole derivative. In contrast, the reaction of acetylenedicarboxylic acid and its derivatives with 2-aminoarenetellurols generated 1,4-tellurazepinones, including a derivative of novel tricyclic naphtho [1, 4]tellurazinone. A comparison with analogous reactions of sulfur congeners indicates that their chemistry is a good predictor for the products obtained from 2-aminoarenetellurols. Selected compounds were characterized by X-ray crystallography. The present work offers access to previously unexplored organotellurium heterocycles.
A Remarkably Efficient Phase-Transfer Catalyzed Amination of α-Bromo-α, β-Unsaturated Ketones in Water
Tandem conjugate addition–alkylation reaction of various amines with α-bromo-α, β-unsaturated ketones resulted in near-quantitative conversions into the corresponding aziridines when the reaction was carried out in the presence of 10 mol% of phase-transfer, PT catalysts in water. Some chiral quaternary ammonium salts derived from Cinchona alkaloids were investigated as water-stable PT catalysts. The scope and limitations of the reaction have also been investigated. The catalytic performances were significantly improved in comparison with the corresponding ordinary quaternary ammonium salt catalysts, and excellent yields (81%–96%) were obtained. Although an increase in the rate of aziridination has been accomplished, no stereoselectivity was observed. The positive values of the protocol have been confirmed.
Understanding the Mechanism and Selectivities of the Reaction of Meta-Chloroperbenzoic Acid and Dibromocarbene with β-Himachalene: A DFT Study
This study was performed to understand the site selectivity in the reaction between β-himachalene and meta-chloroperbenzoic acid (m-CPBA) in the first step followed by the addition of dibromocarbene (CBr2) to the main monoepoxidation product Pα formed in the first reaction. Calculations were performed using the Becke three-parameter hybrid exchange functional and the Lee–Yang–Parr correlation functional (B3LYP) with the 6-311 + G (d, p) basis set. Transition states were located by QST2, and their highlighting was validated by the existence of only one imaginary frequency in the Hessian matrix. The action of m-CPBA on β-himachalene was analyzed on the two double bonds of β-himachalene whose theoretical calculations show that the attack affects the most substituted double bond on α side containing hydrogen of ring junction. The obtained Pα product thereafter treated with dibromocarbene leads via an exothermic reaction to the six-membered ring double bond position of α-monoepoxide. The major products Pαα are kinetically and thermodynamically favored with a high stereoselectivity in perfect correlation with the experimental observations.
Synthesis of Some Novel Fluorinated/Nonfluorinated α-Amino Acids, Bearing 3-Thioxo-5-oxo-1,2,4-triazin-6-yl and Steroidal Moieties, and Evaluation of Their Amylolytic Effects against Some Fungi, Part-II
Some new fluorinated/nonfluorinated α-amino acids bearing 3-thioxo-5-oxo-1,2,4-triazin-6-yl and steroidal moieties have been obtained from condensation of the corresponding amino-triazinones with the steroid (Epiandrosterone). This was followed by the addition of HCN and, finally, acidic hydrolysis. The structure of the targets was established from their elemental analysis and spectral data. The amylolytic activity of the new products was evaluated against some fungi.
Synthesis of Organic Ligands via Reactions of 4-Benzoyl-5-phenylamino-2,3-dihydrothiophene-2,3-dione with N-Nucleophiles
The reaction of 4-benzoyl-5-phenylamino-2,3-dihydrothiophene-2,3-dione (1) with aminoheteroaryls, lamotrigine, 1,3-diaminoheteroaryls, dapsone, NH2R (hydroxylamine, DL-1-phenylethylamine, and metformin), and 4,4′-bipyridine in THF/H2O (1 : 1) at room temperature led to 3-N-phenylthiocarbamoyl-2-butenamides 2–5, while that with naphthylamines and 1,3-phenylenediamine in ethanol at high temperature led to 5-phenylamino-2,5-dihydrothiophene-2-ones 6–8 as organic ligands in the medium to good yields. These showed the nucleophilic attacks of N-nucleophiles, except primary aromatic amines, on thioester carboxyl group (C-2) of thiophene-2,3-dione ring 1. However, the nucleophilic attacks of primary aromatic amines on the carbonyl group (C-3) of thiophene-2,3-dione 1 occurred in the form of substituted thiophenes.
Efficient ZrO(NO3)2.2H2O Catalyzed Synthesis of 1H-Indazolo[1,2-b] phthalazine-1,6,11(13H)-triones and Electronic Properties Analyses, Vibrational Frequencies, NMR Chemical Shift Analysis, MEP: A DFT Study
The synthesis of 1H-indazolo[1,2-b]phthalazine-1,6,11(13H)-trione derivatives, using one-pot three-component condensation reaction of 3-nitrophthalic anhydride, hydrazine monohydrate, dimedone, and aromatic aldehydes in the presence of ZrO(NO3)2.2H2O as the novel catalyst and in reflux conditions in EtOH was reported. Quantum theoretical calculations for three structures of compounds (5a, 5b, and 5c) were performed using the Hartree–Fock (HF) and density functional theory (DFT). From the optimized structure, geometric parameters were obtained and experimental measurements were compared with the calculated data. The structures of the products were confirmed by IR, 1H NMR, 13C NMR, mass spectra, and elemental analyses. The IR spectra data and 1H NMR and 13C NMR chemical shift computations of the 1H-indazolo[1,2-b]phthalazine-1,6,11(13H)-trione derivatives in the ground state were calculated. Frontier molecular orbitals (FMOs), total density of states (DOS), thermodynamic parameters, and molecular electrostatic potential (MEP) of the title compounds were investigated by theoretical calculations. Molecular properties such as the ionization potential (I), electron affinity (A), chemical hardness (η), electronic chemical potential (µ), and electrophilicity (ω) were investigated for the structures. Thus, there was an excellent agreement between experimental and theoretical results.