R4NHal/NOHSO4: A Usable System\nfor Halogenation of Isoxazoles, Pyrazoles, and Beyond

A new\nconvenient and versatile halogenating system (R4NHal/NOHSO4), giving straightforward and general access\nto halogenated 3,5-diaryl- and alkylarylisoxazoles, pyrazoles and electron-rich benzenes from\nthe corresponding scaffolds, is suggested. The method provides excellent\nregioselectivity, scalability to the gram scale, and a broad scope\nfor both aromatics and halogens. A three-step, one-pot reaction protocol\nwas developed, and a series of 3,5-diaryl-4-haloisoxazoles has been\nefficiently synthesized from 1,2-diarylcyclopropanes under suggested\nnitrosating–halogenating conditions.