Zwitterionic imidazolium salt: An efficient organocatalyst for tetrahydropyranylation of alcohols

An aprotic imidazole based zwitterionic-salt, 4-(3-methylimidazolium)-butane sulfonate has been found to be an efficient organocatalyst for tetrahydropyranylation by the reaction of 3,4-dihydro-2H-pyran (DHP) and different aliphatic alcohols as well as various phenolic compounds. The notable advantages of the present method are general applicability to various alcohols, clean reaction, production of no hazardous waste, open air reaction conditions and high yields. The catalyst can be reused without the loss of significant catalytic activity.     

Ligand-Mediated Revival of Degraded α-CsPbI3 to Stable Highly Luminescent Perovskite

Although α-CsPbI₃ is regarded as an attractive optical luminophore, it is readily degraded to the optically inactive δ-phase under ambient conditions. Here, we present a simple approach to revive degraded (“optically sick”) α-CsPbI₃ through “medication” with thiol-containing ligands. The effect of different types of thiols is systematically studied through optical spectroscopy. The structural reconstruction of degraded α-CsPbI₃ nanocrystals to cubic crystals in the presence of thiol-containing ligands is visualized through high-resolution transmission electron microscopy and supported by X-ray diffraction analysis. We found that 1-dodecanethiol (DSH) effectively revives degraded CsPbI₃ and results in high immunity towards moisture and oxygen, hitherto unreported. DSH facilitates the passivation of surface defects and etching of degraded Cs₄PbI₆ phase, thus reverting them back to the cubic CsPbI₃ phase, leading to enhanced PL and environmental stability.     

Solvent free,fast and asymmetric Michael additions of ketones to nitroolefins using chiral pyrrolidine–pyridone conjugate bases as organocatalysts

New chiral organocatalysts are envisaged based on a pyrrolidine–pyridone conjugate and synthesized from commercially available proline employing standard protocols. These catalysts were found to be useful for asymmetric Michael additions of ketones to nitroolefins to afford the desired products in very good yields (up to 98%) with excellent diastereo- and enantioselectivities (>97:3 syn/anti and up to 98% ee) in very short reaction time compared with the existing reports.     

Optical properties of Dy3+ doped in oxyfluoroborate glass

Optical absorption, fluorescence and photoacoustic spectra of Dy3+ doped in oxyfluoroborate glass has been studied. Lifetime of 4F(9/2) level has been measured for different concentration of Dy3+. Effect of concentration quenching on the lifetime and the fluorescence yield has been observed and the mechanism of energy transfer discussed. The energy transfer from Pr3+ to Dy3+ has been observed and explained in a codoped glass containing Pr3+ + Dy3+.     

Synthesis of diverse β-(nitrooxy)-substituted amines by regioselective ring-opening of aziridines under neat conditions

An efficient and regioselective method was developed for the synthesis of β-(nitrooxy)-substituted amine derivatives by ring-opening of different aziridines with Zn(NO₃)₂·6H₂O without using additives or catalyst. A library of β-(nitrooxy)-substituted amine derivatives having a variety of substituents has been synthesized. Excellent regioselectivity, high yields, clean reaction, ease of product isolation, easily accessible reactants, and solvent-free as well as environment friendly reaction conditions are the notable advantages of the present methodology. The nitrooxy derivative was successfully transformed into hydroxy derivative by simple reduction. Gram-scale synthesis demonstrates the potential applications of the present method.