Ring-closing iodoamination of homoallylic amines for the synthesis of polysubstituted pyrrolidines: application to the asymmetric synthesis of (-)-codonopsinine

Ring-closing iodoamination of (E)-configured, N-α-methyl-p- methoxybenzyl protected homoallylic amines upon treatment with I 2 and NaHCO 3 in MeCN occurs with concomitant loss of the N-α-methyl-p-methoxybenzyl group to give 3-iodopyrrolidines in >99:1 dr. This transformation was used as one of the key steps in the total asymmetric synthesis of (-)-codonopsinine, which was achieved in seven steps (from commercially available tert-butyl crotonate) in 5% overall yield and >99:1 dr. © 2012 Elsevier Ltd. All rights reserved