KF/Al2O3: Solid-Supported Reagent Used in 1,3-Dipolar Cycloaddition Reaction of Nitrile Oxide

The stereoselective synthesis of 2-isoxazolidine through 1,3-dipolar cycloaddition reaction of nitrile oxide, which is in situ generation from aldoxime in the presence of N-bromosuccinamide and solid-supported reagent KF/Al₂O₃ at room temperature, is reported. KF/Al₂O₃ is sufficiently basic such that it can replace organic bases such as Et₃N used in typical procedures and it catalyses the reaction to enhance the rate of the reaction.     

Stimulated emission depletion microscopy with a supercontinuum source and fluorescence lifetime imaging

We demonstrate stimulated emission depletion (STED) microscopy implemented in a laser scanning confocal microscope using excitation light derived from supercontinuum generation in a microstructured optical fiber. Images with resolution improvement beyond the far-field diffraction limit in both the lateral and axial directions were acquired by scanning overlapped excitation and depletion beams in two dimensions using the flying spot scanner of a commercially available laser scanning confocal microscope. The spatial properties of the depletion beam were controlled holographically using a programmable spatial light modulator, which can rapidly change between different STED imaging modes and also compensate for aberrations in the optical path. STED fluorescence lifetime imaging microscopy is demonstrated through the use of time-correlated single photon counting.     

Lewis Acid Catalysed Chemoselective Amination of Alcohols Using Heterocyclic Thiones: An Avenue to Thiotetrazole Derivatives

Herein,a protocol for the chemoselective formation of C−N bond using Cu(OTf)₂ as catalyst has been described using heterocyclic thiones. The reaction occurs preferentially at the nitrogen centre over the sulphur atom leading to C−N bond formation. Water being the only by-product, the reaction is environmentally friendly. The reaction proceeds without any additive, ligand or inert atmosphere and shows good tolerance towards variety of alcohols and thiotetrazole derivatives. Our developed protocol could be scaled up to gram scale efficiently, which highlights the efficacy of this method and might offer potential application in synthetic industry.