Cycloaddition Reactions of Nitrile Oxides with Alkenes

Abstract

This chapter reviews the cycloaddition reactions of nitrile oxides with alkenes. It covers the literature published between 1985 and 1992. The chapter emphasizes on the dramatic improvements in the degree of stereocontrol that has been attained in intermolecular reactions and to the developments in the use of intramolecular nitrile oxide cycloaddition (INOC) reactions, where the predisposition of the reacting groups within a molecule greatly enhances the regio and stereo-selectivity. The synthesis of benzonitrile oxide by chlorination of benzaldoxime, in order to give benzhydroximinoyl chloride followed by dehydrohalogenation with sodium carbonate forms the basis of the most common approach for the synthesis of nitrile oxides. The reactions of nitrile oxides with alkenes are essentially 1,3-dipolar cycloadditions and their mechanism have been subject of numerous investigations. The chapter also describes reactivity, regioselectivity, stereoselectivity, and the uses of isoxazolines. In specific, cycloaddition rates range over several orders of magnitude and to predict the likely success of a reaction, when alternative reaction pathways, such as nitrile oxide dimerization are possible, it becomes necessary to understand the reactivity of the system.