N-3-Alkenyl carbamates, which are readily available in enantiomerically pure form, undergo a stereoselective intramolecular coupling under the effect of a Cp2ZrCl2/2n-BuLi reagent. The influence of the carbamate structure on the stereoselectivity was tested. The reaction gives an easy access to various di-and trisubstituted enantiopure pyrrolidinones. (c) 2007 Elsevier Ltd. All rights reserved.
Indium-Mediated Asymmetric Barbier-Type Allylation of Aldimines in Alcoholic Solvents: Synthesis of Optically Active Homoallylic Amines
Chiral aldimines derived from phenylglycinol were diastereoselectively allylated with indium powder/allyl bromide in alcoholic solvents. Both aliphatic and aromatic aldimines provided good yield of the desired products with high diastereoselectivity. A racemization-free protocol for removal of the phenylglycinol auxiliary was also developed. The stereochemical assignment of the homoallylic amine was