CuO nanoparticles catalyzed simple and efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones and quinazolin-4(3H)-ones under ultrasound irradiation in aqueous ethanol under ultrasound irradiation in aqueous ethanol

A CuO nanoparticle-catalyzed one-pot process has engineered for the preparation of diverse quinazolinones from the readily available isatoic anhydride, aldehydes and amine or ammonium. For amine substrates the reactions afford 2,3-dihydroquinazolin-4(1H)-ones in aqueous ethanol promoted by ultrasound irradiation. However, the ammonium substrates undergo intramolecular electron transfer and rearrangement yielding quinazolin-4(3H)-ones. The catalyst is recyclable four times without loss of substantial activity. Other remarkable features include the wide range of functional group tolerance (46 quinazolinones are synthesized and 9 of them are reported firstly), and providing moderate to excellent yield of the products under mild conditions.     

Gallium(III) triflate-catalyzed one-pot selective synthesis of 2,3-dihydroquinazolin-4(1H)-ones and quinazolin-4(3H)-ones

A series of 2,3-dihydroquinazolin-4(1H)-ones and quinazolin-4(3H)-ones have been synthesized in good to excellent yields and high selectivity by one-pot reaction using isatoic anhydride, ammonium acetate (or amines), and aldehydes in ethanol or in DMSO under mild conditions, respectively. The reaction was efficiently promoted by 1 mol % Ga(OTf)₃ and the catalyst could be recovered easily after the reactions and reused without evident loss of reactivity.     

Efficient one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-ones from aromatic aldehydes and their one-pot oxidation to quinazolin-4(3H)-ones catalyzed by Bi(NO3)3·5H2O: Investigating the role of the catalyst

An efficient and novel synthesis of 2,3-disubstituted 2,3-dihydroquinazolin-4(1H)-ones via one-pot, three-component reaction of isatoic anhydride, primary amines and aromatic aldehydes catalyzed by Bi(NO₃)₃·5H₂O under solvent-free conditions is described. Oxidation of these 2,3-dihydroquinazolin-4(1H)-ones to their quinazolin-4(3H)-ones was also successfully performed in the presence of Bi(NO₃)₃·5H₂O. This new method has the advantages of convenient manipulation, short reaction times, excellent yields, very easy work-up, and the use of commercially available, low cost and relatively non-toxic catalyst. The role of Bi(NO₃)₃·5H₂O was also investigated in these transformations.     

NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO4)2·12H2O (M=Rb and Cs) single crystals

The physical properties and phase transition mechanisms of MCr(SO₄)₂·12H₂O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T₁ of the ⁸⁷Rb and ¹³³Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the ⁸⁷Rb and ¹³³Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T₁ are related to variations in the symmetry of the octahedra of water molecules surrounding Rb⁺ and Cs⁺. We also compared these ⁸⁷Rb and ¹³³Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO₄)₂·12H₂O and MAl(SO₄)₂·12H₂O crystals.     

A facile and rapid access towards the synthesis of 2,3-dihydroquinazolin-4(1H)-ones

An efficient synthetic route for 2,3-dihydroquinazolin-4(1H)-ones using 2-morpholinoethanesulfonic acid as a potential and new organocatalyst is described. The developed synthetic protocol represents a novel and very simple route for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives. In addition, microwave irradiation technique is successfully implemented for carrying out the reactions in shorter reaction times.     

Supported ceric ammonium nitrate: A highly efficient catalytic system for the synthesis of diversified 2,3-substituted 2,3-dihydroquinazolin-4(1H)-ones

A practically expeditious protocol has been developed for the cascade synthesis of 2,3-dihydroquinazolin-4(1H)-ones via the condensation of 2-aminobenzamide/2-aminobenzanilide and aromatic aldehydes using a catalytic amount of silica-supported ceric ammonium nitrate. This method affords rapid transformation at room temperature with good to excellent yields.     

Ethylenediamine diacetate-catalyzed three-component reaction for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and their spirooxindole derivatives

Ethylenediamine diacetate (EDDA)-catalyzed one-pot syntheses of biologically interesting 2,3-dihydroquinazolin-4(1H)-ones and their spirooxindole derivatives from isatoic anhydride, amines, and benzaldehydes or isatins via a three-component condensation in aqueous media have been described. This method is of great value because of high yields and ease of handling.     

Amberlyst-15 mediated synthesis of 2-substituted 2,3-dihydroquinazolin-4(1H)-ones and their crystal structure analysis

An efficient and clean method has been developed for the synthesis of 2-substituted 2,3-dihydroquinazolin-4(1H)-ones using Amberlyst-15 as a recyclable catalyst. A variety of dihydroquinazolinones were prepared from 2-aminobenzamide and aldehydes under mild conditions in excellent yields. Further structure elaboration of one compound and the crystal structure analysis and hydrogen bonding patterns of the two compounds prepared by using this methodology is presented.     

Two Ce(SO4)2·4H2O polymorphs: Crystal structure and thermal behavior

Syntheses, crystal structures and thermal behavior of two polymorphic forms of Ce(SO₄)₂·4H₂O are reported. The first modification, α-Ce(SO₄)₂·4H₂O (I), crystallizes in the orthorhombic space group Fddd, with a=5.6587(1), b=12.0469(2), c=26.7201(3) Å and Z=8. The second modification, β-Ce(SO₄)₂·4H₂O (II), crystallizes in the orthorhombic space group Pnma, with a=14.6019(2), b=11.0546(2), c=5.6340(1) Å and Z=4. In both structures, the cerium atoms have eight ligands: four water molecules and four sulfate groups. The mutual position of the ligands differs in (I) and (II), resulting in geometrical isomerism. Both these structures are built up by layers of Ce(H₂O)₄(SO₄)₂ held together by a hydrogen bonding network. The dehydration of Ce(SO₄)₂·4H₂O is a two step (I) and one step (II) process, respectively, forming Ce(SO₄)₂ in both cases. During the decomposition of the anhydrous form, Ce(SO₄)₂, into the final product CeO₂, intermediate xCeO₂·yCe(SO₄)₂ species are formed.     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Alumina supported-CeCl3·7H2O-NaI: an efficient catalyst for the cyclization of 2′-aminochalcones to the corresponding 2-aryl-2,3-dihydroquinolin-4(1H)-ones under solvent free conditions

We recently advanced silica gel supported-TaBr₅ as an efficient catalyst for the isomerization of 2′-aminochalcones to the corresponding 2-aryl-2,3-dihydroquinolin-4(1H)-ones under solvent free conditions (Tetrahedron Lett. 2006, 47, 2725-2729). This conversion can be further improved through the use of more economic alumina supported-CeCl₃·7H₂O-NaI, providing high yields of up to 98% at lower reaction temperatures. This stable catalyst is easily prepared, active under solvent-free conditions and employed under environmentally friendly conditions.     

Ferric sulfate [Fe2(SO4)3·xH2O]: an efficient heterogeneous catalyst for the synthesis of tetrahydroquinoline derivatives using Povarov reaction

Fe₂(SO₄)₃·xH₂O can be used as an efficient and reusable catalyst for the synthesis of pyrano- and furanotetrahydroquinolines via one-pot three-component Povarov reaction involving aromatic aldehydes, aromatic amines, and cyclic enol ethers. The catalyst is recyclable, economically viable, and environmentally benign. This protocol provides good yields and diastereoselectivity as well as applicability on a wide range of substrates.     

Cu(OTf)2: a reusable catalyst for high-yield synthesis of 3,4-dihydropyrimidin-2(1H)-ones

Copper(II) triflate catalyzes efficiently the three-component condensation reaction of an aldehyde, β-ketoester and urea in acetonitrile to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones in high yields. The catalyst exhibited remarkable reusable activity.     

Preparation, spectroscopic properties of 1,4-di (N,N-diisopropylacetamido)-2,3(1H,4H)-quinoxalinedione (L) lanthanide complexes and the supramolecular structure of [Nd2L2(NO3)6(H2O)2]·H2O

The reaction of lanthanide nitrate with 1,4-di (N,N-diisopropylacetamido)-2,3(1H,4H)-quinoxalinedione (L) yields six novel Ln(III) complexes ([Ln₂L₂(NO₃)₆(H₂O)₂]·H₂O) which are characterized by elemental analysis, thermogravimetric analysis (TGA), conductivity measurements, IR, electronic and ¹H NMR spectroscopies. A new quinoxalinedione-based ligand is used as antenna ligand to sensitize the emission of lanthanide cations. The lowest triplet state energy level of the ligand in the nitrate complex matches better to the resonance level of Eu(III) and Sm(III) than Tb(III) and Dy(III) ion. The f-f fluorescence is induced in the Eu³⁺ and Sm³⁺ complexes by exciting into the π-π* absorptions of the ligand in the UV. Furthermore, the crystal structures of a novel binuclear complex [Nd₂L₂(NO₃)₆(H₂O)₂]·H₂O has been determined by single-crystal X-ray diffraction. The binuclear [Nd₂L₂(NO₃)₆(H₂O)₂]·H₂O complex units are linked by the intermolecular hydrogen bonds and π-π interactions to form a two-dimensional (2-D) layer supramolecule.     

An efficient stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes from unactivated Baylis-Hillman adducts using NaBH4/CuCl2·2H2O

A convenient and facile stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes has been achieved by treatment of unactivated Baylis-Hillman adducts with NaBH₄ in the presence of CuCl₂·2H₂O at room temperature for 15 min.     

Ionic liquid promoted synthesis of 3-(2′-benzothiazolo)-2,3-dihydroquinazolin-4(1H)-ones

3-(2′-Benzothiazolo)-2,3-dihydroquinazolin-4(1H)-ones have been synthesized in high yields in the presence of 1-butyl-3-methylimidazolium bromide [bmim]Br as an ionic liquid; the reaction work-up is simple and the ionic liquid can be easily separated from the product and reused.     

Thiamine hydrochloride (VB1) as an efficient promoter for the one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-ones

A facile, efficient, and environmentally friendly procedure for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones from isatoic anhydride, aldehyde, and ammonium acetate in the presence of thiamine hydrochloride (VB₁) in EtOH is described. The protocol proves to be efficient and environmentally benign in terms of high yields, ease of recovery, and reusability of catalyst.     

Fe2(SO4)3·xH2O-catalyzed per-O-acetylation of sugars compatible with acid-labile protecting groups adopted in carbohydrate chemistry

Fully acetylated saccharides are inexpensive and very useful starting materials for the synthesis of many naturally occurring glycosides, oligosaccharides, and glycoconjugates. Ferric sulfate hydrate (Fe₂(SO₄)₃·xH₂O) was found to be a valuable Lewis acid promoter in the per-O-acetylation reaction of saccharides with acetic anhydride in 100% of conversion rate and 88-99% yields. Interestingly, the procedure is perfectly compatible with the presence of a variety of acid-labile protecting groups, such as isopropylidene, benzylidene, trityl, and TBDMS groups. The reactions were simply performed by stirring the mixture of a sugar with a slight excessive acetic anhydride in the presence of 2.0 mol % of Fe₂(SO₄)₃·xH₂O at rt and the pure products were obtained by a simple dilution of the reaction mixture with dichloromethane and washings with aqueous Na₂CO₃.     

Copper-catalyzed one-pot synthesis of 2-thioxo-2,3-dihydroquinazolin-4(1H)-ones from ortho-bromobenzamides and isothiocyanates

Copper-catalyzed tandem reaction of ortho-bromobenzamides and isothiocyanates is described, which provides an efficient and practical route for the synthesis of 2-thioxo-2,3-dihydroquinazolin-4(1H)-ones. The optimal condition involved the following parameters: CuI as precatalyst, Cs₂CO₃ as base, N,N′-dimethylethane-1,2-diamine as ligand, and toluene as solvent, with reaction temperature at 120 °C.     

Synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by α-chymotrypsin

We discovered that α-chymotrypsin has a promiscuous ability to catalyze the cyclocondensation of aromatic and aliphatic aldehydes with 2-aminobenzamides to afford the corresponding 2,3-dihydroquinazolin-4(1H)-ones successfully in high yields (90%-98%) under alcohol solvent. The catalytic activity of α-chymotrypsin was evaluated through investigating the temperature, the enzyme loading and the ratio of substrates in the enzyme-catalyzed reactions. The present method proves to be efficient and environmentally friendly in terms of short reaction time, high yield, green catalyst and the clean products obtained without further purification processes.