Highly Selective Synthesis of Dihydrobenzo[<i>d</i>]isoxazoles and Dihydrobenzo[<i>d</i>]oxazoles from Oximes and Arynes via in Situ Generation of Nitrones

An efficient method for the synthesis of dihydrobenzo­[d]­isoxazoles and dihydrobenzo­[d]­oxazoles bearing a quaternary carbon center has been developed. The reaction involves generation of a ketonitrone intermediate in situ from a ketoxime and an aryne. A novel thermal rearrangement of the dihydrobenzo­[d]­isoxazole products to the corresponding dihydrobenzo­[d]­oxazoles has been observed. These transformations tolerate a variety of functional groups and offer a rapid and efficient way to diverse dihydrobenzo­[d]­isoxazoles and dihydrobenzo­[d]­oxazoles under mild transition-metal-free conditions.