Classical and advanced chemical sciences
One-pot solvent free three components coupling of aryl aldehydes, β-dicarbonyl compounds, urea or thiourea was performed to afford corresponding 3,4-dihydropyrimidine-2-ones and their sulfur analogs 3,4-dihydro-pyrimidine-2-thiones. It is the first report of BF3.ACN catalyzed the solvent-free synthesis of pyrimidone analogs.
Keywords: BF3.ACN, solvent-free, 3,4-dihydropyrimidine-2-one
An easy and efficient protocol for oxidative synthesis of quinazolinones and benzoxazinones using novel catalyst fromed in- situ from chromium trioxide has been developed. Here chromium trioxide acts as an oxidant and its reduction products catalyze the coupling reaction. Newly developed method demonstrates a new alternative to existing method which is a cost effective approach to synthesize important moieties like quinazolinones and benzoxazinones from easily available starting materials in good to excellent yields.
Keywords: quinazolinones; benzoxazinones; chromium trioxide; catalyst; oxidant
The system of triple In1–xGaxAs continuous solid solutions allows the solution of the many problems of modern semiconductor technology as microelectronics, optoelectronics, and nanoelectronics. The remarkable manufactural properties of ternary In1-XGaXAs solid solutions make them very useful nanotech performance materials for manufacture nanotech products, such as nanowires, nanotubes, etc. For successful solution of this problem, it is necessary to reveal their intrinsic properties and eliminate the effect of structural imperfections existing in thin films and layers, which is possible by investigating crystals of In1–xGaxAs solid solutions in bulk form. The complete miscibility of components in the solid and liquid state and the linear dependence of lattice parameter on the composition of In1–xGaxAs solid solutions allow to consider this system as a pseudo-binary alloys system of two components of (GaAs)x and (InAs)1–x like SiGe alloys system. This feature of the alloys has enabled to apply the comparatively affordable and straightforward method of direct fusion process of InAs and GaAs components for producing of In1–xGaxAs alloys with stable chemical composition. Carefully selected conditions of the fusion and processing of crystal growth have allowed obtaining several compositions of InAs-rich In1–xGaxAs alloys with uniform distribution of components across the ingot of single crystal by one fusion.
Keywords: ternary alloys, segregation, fusion, crystallization, compounds
Following the discovery of an unprecedented transamination reaction between primary alkylamines and a quinonoid molecule of the type C6H2(NHCH2R)2(=O)2 (I), obtained from commercially available diaminoresorcinol.2HCl, we have extended this method to the use of primary arylamines and found that, in contrast, secondary amines led to a different outcome. Whereas functionalized molecules of type I, which are best described as 6π +6π zwitterions, were obtained with aniline or 4-methoxyaniline, no transamination was observed with tBuNH2 in ethanol. However, a reaction which afforded salt 2-methylpropan-2-aminium 4-(methylamino)-3,6-dioxocyclohexa-1,4-dien-1-olate (2b) took place in water and resulted from hydrolysis of the imine group and deprotonation of 5-hydroxy-2-(methylamino)-4-(methylimino)-cyclohexa-2,5-dienone (1a). Under similar conditions, secondary amines led to comparable results. The cations associated with the anionic quinonoid are readily exchanged in the presence of a primary amine. Whereas for the transamination reaction, basic amines react under mild conditions, slightly harsher conditions are needed for less basic amines such as piperidine, diisopropylamine, or diethylamine. Transamination reactions were also performed with 5-hydroxy-2-(methylamino)-4-(methylimino)-cyclohexa-2,5-dienone (1a), which is more soluble in organic solvents than 2-amino-5-hydroxy-4-iminocyclohexa-2,5-dienone (compound I) This led to the first examples of quinonoidal zwitterions functionalized with different alkyl groups on the nitrogen atoms. A number of compounds were characterized by X-ray diffraction, which allowed a better understanding of their electronic situation, and in many cases, the presence of multiple hydrogen-bond donors and acceptors results in crystal packings dominated by these interactions.
Keywords: C–N activation; hydrogen bonds; quinones; amination; zwitterions
The crystal structure of 2-bromo-4-hydroxypyridine (1) at 120 K is reported. The compound crystallizes in the monoclinic space group C2/c with a = 15.6770(6) Å, b = 3.86471(13) Å, c = 18.0645(7) Å and β = 90.916(3)°. The compound exhibits both the 4-hydroxypyridine and 4-pyridone tautomers as exhibited by the disordered proton which occupies the O-H and N-H positions equally. Hydrogen bonding links the molecules into chains parallel to the ac-face diagonal. Halogen bonds [Br … O = 3.0809(15) Å] roughly parallel to the a-axis link the chains into layers roughly parallel to the bc-face diagonal. π-stacking interactions complete the stabilization of the structure.
Keywords: crystal structure; hydrogen bonding; halogen bonding
An efficient one pot synthesis of pyranopyrazoles has been achieved by the four-component condensation of hydrazine hydrate, ethyl acetoacetate, aldehydes and malononitrile using sodium lactate as a catalyst in aqueous ethanolic medium under reflux condition. The method is simple and green to afford pyranopyrazoles in a short time. It provides a new base catalyst that readily gives product from moderate to excellent yields.
Keywords: catalyst; green synthesis; one pot; pyranopyrazole; sodium lactate