Azetidinium ylides showed a remarkable ability to perform the cyclopropanation of Michael acceptors. Ephedrine-derived azetidinium ylides allowed the formation of substituted cyclopropanes in good yields and at a high level of stereoselectivity. The determination of the relative stereochemistries in the produced cyclopropanes gave some insight into the reaction mechanism.

Azetidinium ylides effected facile epoxidation of various carbonyl compounds furnishing tri or tetrasubstituted epoxides that were unattainable via classical ammonium ylide chemistry; the produced trisubstituted oxiranes gave rise to a remarkable cascade of reactions leading to some original pyrrolidin-3-ones.

Cyclopropane derivatives Q 0021 Strained Azetidinium Ylides: New Reagents for Cyclopropanation. -Treatment of the azetidinium ylides with activated alkenes offers a new and stereoselective approach to cyclopropane derivatives. -(COUTY*, F.; DAVID, O.; LARMANJAT, B.; MARROT, J.; J. Org. Chem. 72 (2007) 3, 1058-1061; Inst. Lavoisier, CNRS, Univ. Versailles St. Quentin, F-78035 Versailles, Fr.; Eng.) -Jannicke 22-056

Oxirane derivatives R 0030Strained Azetidinium Ylides: New Reagents for Epoxidation. -Azetidinium ylides, generated by deprotonation of the corresponding azetidinium salts, effect epoxidation of aldehydes (I) and ketones such as (V) in a diastereoselective manner. Tri-and tetrasubstituted epoxides are obtained that are unattainable via classical ammonium ylide chemistry. The trisubstituted oxiranes (III) give rise to an unexpected rearrangement producing pyrrolidin-3-ones having a quaternary carbon center. -(ALEX, A.; LARMANJAT, B.; MARROT, J.; COUTY, F.; DAVID*, O.; Chem. Commun. (Cambridge) 2007, 24, 2500-2502; Inst. Lavoisier, CNRS, Univ. Versailles St. Quentin, F-78035 Versailles, Fr.; Eng.) -M. Paetzel 44-092