Photocatalytic Generation of Nitrenes for Rapid Diaziridination.

A blue LED, an organic photocatalyst (rose bengal), and the Lewis acid like oxidant PhI(OAc)2 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.

CuBr-ZnI2 Combo-Catalysis for Mild CuI-CuIII Switching and sp2 C-H Activated Rapid Cyclization to Quinolines and Their Sugar-Based Chiral Analogues: A UV-Vis and XPS Study.

An unprecedented CuBr-ZnI2 combo-catalyzed mild Cu1-CuIII switching activation of sp2 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 CuI-CuIII combo-catalysis for a rapid three-component cyclization is expected to proceed through the formation of a flexible propargyl amine intermediate, which provides a CuI-procatalyst for rapid sp2 C-H activation with cyclization involving transient CuIII species. The in situ generation of transient CuIII species was confirmed through online ultraviolet-visible spectroscopy (UV-vis), electrospray ionization mass spectrometry (ESI-MS), and X-ray photoelectron spectroscopy (XPS) analyses.