INTERACTIONS BETWEEN 1,3-DIPOLES AND META L-IONS - STEREOCONTROL AND REGIOCONTROL OF 1,3-DIPOLAR CYCLOADDITION REACTIONS

This review focuses on our own attempts of metal ion-assisted stereo- and regiocontrol of 1,3-dipolar cycloaddition reactions: N-Metalated a zomethine ylides, or metal enolates, of alkylideneamino nitriles and e sters undergo endo-selective cycoadditions to alpha, beta-unsaturated carbonyl acceptors to give 1-pyrrolines and pyrrolidines. Magnesium al lylic alkoxides are highly reactive in nitrile oxide cycloadditions wh ich are exclusively syn-selective and regioselective. Equally fruitful are nitrone cycoadditions to allylic alkoxides and Lewis acid-catalyz ed nitrone reactions with allylic alcohols and enones.