Enantioselective Binaphthophosphepine‐Promoted [3+2] Annulations of <i>N</i>‐Ts‐ and <i>N</i>‐DPP‐Imines with Allenoates and 2‐Butynoates

Abstract

Abstract The use of binaphthophosphepine 1a as a catalyst for the [3+2] cyclisation between allenoates or 2‐butynoates andimines was investigated. The effects of the imine protecting group on both the catalytic activity and enantioselectivity were determined by comparing the behaviour of N ‐tosyl‐ and N ‐DPP‐imines. The N ‐DPP‐imines displayed lower reactivity, but afforded the desired pyrrolines in higher enantiomeric excess (73–92 % ee ). The DPP protecting group was removed from the final pyrrolines under mild conditions to afford the corresponding secondary amines. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)