A highly diastereoselective synthesis of 3-carbethoxy-2,5-disubstituted-3-pyrrolines by phosphine catalysis

Tributylphosphine was used as catalyst to facilitate a [3+2] cycloaddition between gamma-substituted allenoates and N-sulfonylimines. The resulting adducts, 3-carbethoxy-2,5-disubstituted-3-pyrrolines were formed in excellent yields with high diastereoselectivity. The reaction went to completion in several hours at room temperature, and the starting materials were easily prepared with one step from commercially available compounds via known procedures. (c) 2005 Elsevier Ltd. All rights reserved.