A rapid synthesis of isoxazolo[5,4-d]pyrimidin-4（5H）-ones under microwave irradiation with solid acid catalysis in solvent-free conditions

A rapid and efficient method for the synthesis of isoxazolo[5,4-d]pyrimidin-4（5H）-ones has been developed through cyclocondensation of 5-aminoisoxazole-4-carboxamides with orthoesters under conventional heating and solvent-free microwave irradiation with solid acid catalysis. In comparison, the reactions are faster and the yields are higher under microwave irradiation.     

Potassium phthalimide promoted green multicomponent tandem synthesis of 2-amino-4H-chromenes and 6-amino-4H-pyran-3-carboxylates

A one-pot efficient, green, practical, and environmentally friendly multicomponent synthesis of 5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromenes, ethyl-6-amino-4-aryl-5-cyano-2-methyl-4H-pyran-3-carboxylates as well as 2-amino-4-aryl-7-hydroxy-4H-chromene-3-carbonitriles via tandem the Knoevenagel-cyclocondensation has been described in the presence of a green, low-cost, mild, efficient, and commercially available potassium phthalimide as the organocatalyst. This technique is a safe and ecofriendly approach to the synthesis of different 4H-chromens and 4H-pyrans that offers many merits including short reaction times, high yields, straightforward work-up, and no use of hazardous organic solvents.     

Air-stable zirconium (IV)-salophen perfluorooctanesulfonate as a highly efficient and reusable catalyst for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones under solvent-free conditions

An air-stable complex of zirconium (IV)-salophen perfluorooctanesulfonate ( 1 ) was successfully synthesized by reacting Zr (salphen)Cl₂ and C₈F₁₇SO₃Ag. Complex 1 was characterized and studied by different techniques (NMR, IR, HRMS, TG-DSC, conductivity and acidity measurements), and was found to be air-stable, water tolerant, thermally stable and strongly Lewis-acidic. Complex 1 exhibited high catalytic efficiency for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones via the Biginelli reaction of aldehydes, 1,3-dicarbonyl compounds and urea/thiourea under solvent-free conditions. Furthermore, complex 1 could be reused 5 times with minimal changes in catalytic efficiency. Compared with previously reported methods, the important features of this protocol are the solvent-free conditions, the short reaction times, the wide substrate compatibility, the high efficiency and the good reusability.     

Imidazol-1-yl-acetic acid as a novel green bifunctional organocatalyst for the synthesis of 1, 8-dioxooctahydroxanthenes under solvent-free conditions

Imidazol-1-yl-acetic acid is introduced as a new, efficient and recyclable green bifunctional organocatalyst for the synthesis of 1,8-dioxooctahydroxanthenes under solvent-free conditions. This catalyst is water soluble and can be separated from the products by simple filtration. The filtrate can be evaporated to dryness and recrystallized from cool methanol to give the recovered catalyst. This organocatalyst was used for the synthesis of 1,8-dioxooctahydroxanthenes under solvent-flee conditions and recycled up to 8 consecutive runs without any losing of its efficiency.     

Silver-catalyzed highly efficient synthesis of pyrido[1,2-a]pyrimidin-4-ones from 2-aminopyridines and alkynoates

Pyrimidinone is one of the important nitrogen containing heterocycles due to their wide range of bioactivities. An efficient silver-catalyzed intermolecular cyclization of 2-aminopyridines with various alkynoates has been developed. 2-Substituted 4H-pyrido[1,2-a]pyrimidin-4-ones containing a wide range of functional groups are synthesized in the standard conditions. This transformation is conducted under convenient conditions and affords products in good yields.     

无溶剂条件下勃姆石纳米粒子锅催化多组分合成3,4-二氢嘧啶-2-(1H)酮简

A simple, green, and efficient synthesis protocol for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones using boehmite nanoparticles as catalyst was developed. It did not use any toxic metal catalysts or corrosive acidic reagents. The method gave good to excellent yields and has short reaction time, operational simplicity, and a recyclable catalyst.     

CoNiFe2O4@Silica-SO3H nanoparticles: New recyclable magnetic nanocatalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones under solvent-free conditions

A useful and green synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones derivatives were achieved by one-pot cyclocondensation between substituted aryl aldehydes, diketone/ketoester, and urea/thiourea using magnetic CoNiFe₂O₄@Silica-SO₃H nanoparticles under solvent-free condition. The choice of this approach showed essential advantages such as short reaction time, simple work-up procedure, high activity of the catalyst, high yield of the reaction products, the magnetic properties of the catalyst, and environmentally amiable conditions. In addition, the catalyst recovered and reused four times without notable loss of its activity. The magnetic CoNiFe₂O₄@Silica-SO₃H nanoparticles were described by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and vibrating sample magnetometer. The products were obtained with excellent yields (88–98%). The formation of the products was confirmed and identified with their physical properties (melting points), the FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry, and the elemental analysis.     

A convenient aminolysis of esters catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) under solvent-free conditions

Aminolysis of esters by using the organocatalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is reported. Secondary and tertiary amides were synthesized from alkyl or aryl esters with a variety of primary and secondary amines in good to excellent yields (60-94%) under solvent-free conditions (SFC).     

TaBr5-catalyzed Biginelli reaction: one-pot synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones under solvent-free conditions

An efficient TaBr₅ (5-10 mol %)-catalyzed Biginelli reaction under solvent-free conditions for one-pot syntheses of 3,4-dihydropyrimidin-2-(1H)-ones (DHPMs) and their thione analogs is reported. The catalyst is stable at room temperature and employed under mild and environmentally friendly conditions.     

One-pot synthesis of dihydropyrimidiones catalyzed by strontium(II) triflate under solvent-free conditions

A simple, efficient and practical procedure for the Biginelli reaction using strontium(II) triflate [Sr(OTf)₂] as a novel catalyst is described under solvent-free conditions in high yields. The catalyst exhibited remarkable reactivity and it is reusable. Some of dihydropyrimidiones showed strong pesticidal activity.     

Highly efficient and easy synthesis of 2,4,6-triarylpyridines catalyzed by pentafluorophenylammonium triflate(PFPAT) as a new recyclable solid acid catalyst in solvent-free conditions

Pentafluorophenylammonium triflate(PFPAT) was found to be a highly efficient catalyst for the preparation of 2,4,6- triarylpyridines from the reaction of acetophenone derivatives,aromatic aldehydes and ammonium acetate.Present methodology offers several advantages,such as short reaction time,high yields,simple procedure with an easy work-up and the absence of any volatile and hazardous organic solvent.In addition,this catalytic system can act as an active,inexpensive,metal-free,recoverable and recyclable catalyst.