Nonstabilized Azomethine Ylides in the Mannich Reaction: Synthesis of 3,3-Disubstituted Pyrrolidines, Including Oxindole Alkaloids

Active methylene compounds react with in situ generated nonstabilized azomethine ylides via the domino Mannich reaction-dipolar cycloaddition to form 3,3-disubstituted pyrrolidines, including oxindole alkaloids. When the starting material possesses a single activated hydrogen, the reaction terminates at the Mannich base stage. The developed methodology was applied to a short and efficient synthesis of (+/-)-horsfiline and N-protected (+/-)-coerulescine.