METALLIC BASE-INDUCED AND LEWIS ACID-CATALYZED NITRONE CYCLOADDITIONS TO ALLYL ALCOHOL DIPOLAROPHILES - HIGHLY EFFECTIVE REGIOCONTROL AND STEREOCONTROL

Cycloadditions of N-(benzoylmethylene)aniline N-oxide as a reactive nitrone to allyl alcohol dipolarophiles are accelerated either 1) by pretreatment of the dipolarophiles with an organometallic compound such as ethylmagnesium bromide or diethylzinc, or 2) in the presence of a Lewis acid such as magnesium bromide or zinc bromide. These cycloadditions are highly regio- and stereoselective, both selectivities depending upon the kind of metals included in the organometallics or Lewis acids employed. These reactions offer the first example of regio- and stereocontrol of nitrone cycloadditions to nonactivated olefins.