INFLUENCE OF AG(I) AND LI(I) CATALYSTS FOR 1,3-DIPOLAR CYCLOADDITION REACTIONS OF AZOMETHINE YLIDES - REVERSAL OF THE STEREOCHEMISTRY

摘要

The 1,3-dipolar cycloadditions of ester stabilised azomethin ylides to aryl-nitro olefines catalysed by Li(I) gave products of different stereoselectivity than those arising from processes catalysed by Ag (I). The cycloadditions involve the stereospecific generation of dipoles. The formation of products with reverse stereochemistry when using different metal salt catalysts is caused by the differences in endo and exo approaches of nitro-ethylene compounds. [References: 25]