Diastereoselective Synthesis of Pyrrolidines by 5-Exo-trig Cyclizations of α-Amino Radicals Derived from N-(α-Benzotriazolylalkyl)alkenylamines and Samarium Diiodide

Abstract

The treatment of N-(α-benzotriazolylalkyl)alkenylamines (prepared from γ,δ-unsaturated amines, benzotriazole and aldehydes) with SmI2 generates α-amino radicals and the benzotriazolyl anion. If the alkene portion of the amine is activated by an electron withdrawing substituent an efficient 5-exo-trig radical cyclization takes place to afford mono-, 2,3- and 2,4-disubstituted pyrrolidines with moderate diastereoselectivity. In the absence of the activating group dimerization or radical reduction prevail to the exclusion of cyclization.