Diastereodifferentiation in Intramolecular Cyclopropanations of Chiral Secondary Allylic Diazoacetates.

Abstract Intramolecular cyclopropanations of diastereomeric, secondary allylic diazoacetates were carried out in the presence of an achiral copper catalyst, Cu(TBS) 2 , and the chiral rhodium catalysts Rh 2 [5( S )-MEPY] 4 and Rh 2 [5( R )-MEPY] 4 to give diastereomeric cyclopropyl lactones in ratios that varied with catalysts and stereochemistry of the starting material.