Highly Selective Synthesis of Dihydrobenzo[d]isoxazoles and Dihydrobenzo[d]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.