Highly efficient and stereoselective radical addition of tertiary amines to electron-deficient alkenes - Application to the enantioselective synthesis of necine bases

A convenient and highly efficient method for the regio- and stereoselective addition of tertiary amines to electron-deficient alkenes has been elabora ted. It is based on a radical chain reaction of alpha-aminyl radicals with alkenes, induced by a photoelectron transfer process between tertiary amine s 2a-j and excited electron donor substituted phenyl ketones. The influence of the nature of the amino substituents and of the alkene on the reaction have been examined. In the presence of (5R)-5-menthyloxy-2-(5H)-furanone (1 ) as electron-deficient alkene, the addition of N-alkylpyrrolidines 2a-e oc curred with a complete facial selectivity and up to 94% isolated yields. Th is method has been applied to a fast, efficient and enantioselective synthe sis of necine bases.