A pyridine–pyrazole based fluorescence turn-on chemosensor provides access to selective detection of Al3+ in solution as well as in HepG2 living cells.

A blue LED, an organic photocatalyst (rose bengal), and the Lewis acid like oxidant PhI(OAc) were utilized to generate nitrene intermediates through reactions of 1,2-diols and aliphatic amines under mild reaction conditions. A versatile and rapid diaziridination strategy was established to construct functionalized 1,2-disubstituted diaziridines, diaziridines with chiral substituents, and 1,2,3-trisubstituted analogues with excellent reaction rates, yields, and stereoselectivities. Control and labeling experiments to elucidate the mechanism of this elegant metal-free photocatalyzed cyclization reaction were performed.

An unprecedented CuBr–ZnI 2 combo-catalyzed mild Cu 1 –Cu III switching activation of sp 2 C–H of highly electron-rich arenes is reported. Anilines, aldehydes, and terminal alkynes were rapidly coupled together at ambient temperature to construct a ubiquitous quinoline framework through cyclization of the C≡C bond. This smart solvent-free strategy was exploited for the direct synthesis of valuable 4-substituted, 2,4-disubstituted, and thermally labile sugar-based chiral quinolines in good yields. In contrast to the frequently used imine–alkyne cyclization reaction, this uncommonly mild Cu I –Cu III combo-catalysis for a rapid three-component cyclization is expected to proceed through the formation of a flexible propargyl amine intermediate, which provides a Cu I -procatalyst for rapid sp 2 C–H activation with cyclization involving transient Cu III species. The in situ generation of transient Cu III species was confirmed through online ultraviolet–visible spectroscopy (UV–vis), electrospray ionization mass spectrometry (ESI-MS), and X-ray photoelectron spectroscopy (XPS) analyses.

We have demonstrated a benign strategy for amides, imides and their chiral analogues using water as a source of carbonyl oxygen and medium. DFT-MIR studies and controlled experiments established the mechanism involving PhI(OH)2-bearing intermediates.