Oxidative Approach to Isoxazolines

Significance

Based on an earlier contribution (M. A. Ciufolini and co-workers Org. Lett. 2009, 11, 1539) concerning the oxidation of aldoximes to nitrile oxides utilizing hypervalent iodine reagents, the Ciufolini group reports on the ensuing reaction of the generated 1,3-dipoles with dipolarophiles to produce isoxazolines. Under optimized conditions using methanol containing 0.1-1% of TFA, the [2+3] cycloadditions proceed in poor to good (with styrene) or moderate to excellent (with norbornene) yields. The substrate scope was reasonably well studied, and, refreshingly, mention is made of minute but important details, such as volatility of the products in vacuo.