Diastereoselective pyrrolidine synthesis via copper promoted intramolecular aminooxygenation of alkenes: Formal synthesis of (+)-monomorine

The diastereoselectivity of the copper-promoted intramolecular aminooxygenation of various alkene substrates was investigated. a-Substituted 4-pentenyl sulfonamides favor the formation of 2,5-c/s-pyrrolidines (dr > 20:1) giving excellent yields which range from 76-97% while y-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 a-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.