Diastereoselective Pyrrolidine Synthesis via Copper Promoted Intramolecular Aminooxygenation of Alkenes; Formal Synthesis of (+)-Monomorine

摘要

The diastereoselectivity of the copper-promoted intramolecular aminooxygenation of various alkene substrates was investigated. α-Substituted 4-pentenyl sulfonamides favor the formation of 2,5-cis-pyrrolidines (dr >20:1) giving excellent yields which range from 76–97% while γ-substituted substrates favor the 2,3-trans pyrrolidine adducts with moderate selectivity (ca. 3:1). A substrate whose N-substituent was directly tethered to the α-carbon exclusively yielded the 2,5-trans pyrrolidine. The synthetic utility of the method was demonstrated by a short and efficient formal synthesis of (+)-monomorine.