An Efficient Microwave‐Assisted Synthesis and Antimicrobial Activity of Novel 2‐Amino 3‐Cyano Pyridine Derivatives using Two Reusable Solid Acids as Catalysts

Two solid acids, Fe³⁺ K‐10 montmorillonite clay and HY‐zeolite, have been employed efficiently for synthesis of 2‐amino 3‐cyano pyridines 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l , 4m , 4n , 4o , 4p , 4q , 4r , 4s , 4t , 4u , 4v , 4w , 4x by multicomponent reaction of 3‐acetyl 4‐hydroxy coumarin 1a , 1b , 1c , 1,3‐diphenyl‐1H‐pyrazole‐4‐carbaldehyde 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h , malononitrile 3 , and ammonium acetate. Both the catalysts are recoverable and recyclable. The main significant of this procedure is short reaction time, high yields, easy workup procedure, and being environmentally friendly. The structures of all the compounds have been well characterized by IR, ¹H NMR, ¹³C NMR, and mass spectral data. All the synthesized compounds were screened for their antimicrobial and antifungal activities.     

Low-field DC-magnetization study of Ho-doped Mn–Zn ferrite ferrofluid

The physical and magnetic properties of magnetic nanoparticles are crucial for their effectiveness and reliability in biomedical applications. In this article, we report the synthesis of a stable Ho-substituted Mn–Zn ferrite ferrofluid and its physical and magnetic properties. Substitution by rare earth metal plays an important role in determining the magneto-crystalline anisotropy in 4f-3d inter-metallic compounds. Ho³⁺ substitution not only enhanced the magnetic anisotropy but also produced strong spin frustration at low temperature. The field dependence of blocking temperature shows H^2/3 dependency in the entire range of field, i.e., 10–700 Oe, indicating the emergence of Ising spins characteristics in the present system.     

Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica

Here, we report the design of a hybrid inorganic/organic mesoporous material through simultaneous pore engineering and hydrophobic surface modification of the intramesochannels to improve the uptake of superparamagnetic maghemite nanocrystals via impregnation techniques. The mesoporous material of the SBA-15 type was functionalized in situ with thiol organo-siloxane groups. Restricting the addition of the thiol organo-siloxane to 2 mol % yielded an inorganic/organic hybrid material characterized by large pores and a well-ordered hexagonal p6mm mesophase. The hydrophobic surface modification promoted the incorporation of 7.5 nm maghemite (gamma-Fe2O3) nanocrystals, prepared through temperature-controlled decomposition of iron pentacarbonyl in organic solvents. The hydrophobic, oleic acid capped superparamagnetic maghemite nanocrystals were incorporated into the porous network via wet impregnation from organic suspensions. Combining diffraction, microscopy, and adsorption data confirmed the uptake of the nanocrystals within the intramesochannels of the silica host. Magnetization dependencies on magnetic field at different temperatures show a constriction in the loop around the origin, which indicates immobilization of maghemite nanocrystals inside the thiol-functionalized silica host.     

DBU‐catalyzed Multicomponent Synthesis: Facile Access of 4,5,6,9‐Tetrahydro‐pyrido[3,2‐c]quinolines

An efficient synthesis of 4H,5H,6H,9H‐pyrido[ij]pyrano[3,2‐c]quinolines 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l , 4m , 4n , 4o , 4p , 4q , 4r , 4s , 4t as well as spiro compound 6 was achieved via multicomponent approach by using DBU as a nucleophilic catalyst under the remarkably mild reaction conditions. The structures of the compounds were characterized by ¹H NMR, ¹³C NMR, and mass spectral analysis. An attractive feature of this inexpensive protocol includes facile synthesis, shorter reaction time, ease of work‐up, large number of functional group tolerance, and good to excellent yields with high purity.     

Complex 3D blood flow pathways in two cases of aorta to right heart fistulae: a 4D flow MRI study

We present an analysis of 3D blood flow in two cases of Sinus of Valsalva to right heart fistulae based on 4D flow MRI. Despite similar underlying pathology, 3D visualization revealed intricate differences in flow patterns connecting the systemic and pulmonary circulation. The cases illustrates the potential of 4D flow MRI to complement the evaluation of complex structural heart disease by assessing complex flow dynamics and providing quantitative information of flow ratios and flow rates.     

The fluorescence properties of o-phthalaldehyde derivatives of iodinated amino acids

The preparation and fluorescence properties of o-phthalaldehyde (OPT) derivatives of several iodoamino acids have been studied and compared with those of glycine and tyrosine. Incorporation of successive iodine atoms in the tyrosine and thyronine structures produces increasing quenching of the fluorescence of the OPT derivatives, presumably by the internal heavy atom effect, without significant changes in the spectral distribution. Addition of anti-thyroxine (T4) antiserum to OPT-labelled T4 has no effect on its fluorescence properties.     

Efficient and Rapid Synthesis of Highly Functionalized Novel Symmetric 1,4-Dihydropyridines Using Glacial Acetic Acid as Solvent

A new series of 1,4-dihydropyridines bearing a pyrazole moiety in the 4-position were synthesized by a variation of the classical Hantzsch synthesis. The reaction of 1,3-diphenyl-1H-pyrazole-4-carbaldehyde 4a–n with 3-amino crotononitrile in the presence of glacial acetic acid afforded novel 3,5-dicyano-2,6-dimethyl 1,4-dihydropyridines 5a–n. The procedure has short reaction time (15–20 min), easy workup, and good yield of product. The structures of all synthesized compounds were well characterized by mass, infrared, ¹H and ¹³C NMR, and elemental analysis.