Recent Advances in Intramolecular Nitrile Oxide Cycloadditions in the Synthesis of 2-Isoxazolines

The utility of 2-isoxazolines (Δ2-isoxazolines, 4,5-dihydroisoxazoles) in the preparation of natural products and other compounds of medicinal and materials interest is growing because the 2-isoxazoline serves both as a desirable functional group and a versatile synthetic intermediate. Nitrile oxide cycloaddition (NOC) to alkenes is the most common method for the preparation of 2- isoxazolines, and the intramolecular version of this reaction provides a powerful entry into complex polycyclic systems. This review is the first to compile studies on the intramolecular nitrile oxide cycloaddition (INOC) reaction, with an emphasis on studies from 2000 to 2009. Trends in stereo- and regioselectivity are discussed from observations made in the formation of a wide variety of polycyclic 2- isoxazoline compounds.