Copper(II) Triflate-Catalyzed Intramolecular Hydroamination of Homoallylic Amino Alcohols as an Expedient Route to trans-2,5-Dihydro-1H-pyrroles and 1,2-Dihydroquinolines

✍ Scribed by Weidong Rao; Prasath Kothandaraman; Chii Boon Koh; Philip Wai Hong Chan

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 266 KB
• Volume: 352
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.201000450

✦ Synopsis

Abstract

A new efficient synthetic route to trans‐2,5‐dihydro‐1__H__‐pyrroles and 1,2‐dihydroquinolines that relies on copper(II) triflate‐catalyzed intramolecular hydroamination of homoallylic amino alcohols under mild and operationally straightforward conditions is described. For reactions leading to the trans‐2,5‐dihydro‐1__H__‐pyrrole product, yields of 52–83% along with trans selectivities up to >99:1 dr and ee values up to 97% were accomplished from enantioenriched 1‐(tosylamino)pent‐4‐en‐2‐ols ranging from 91–99% ee. Without the need for inert and moisture‐free conditions, reactions involving 1‐[2‐ (tosylamino)phenyl]but‐3‐en‐1‐ols afforded the corresponding 1,2‐dihydroquinoline products in excellent yields up to 99% and with complete chemoselectivity. The mechanism is suggested to involve cop‐ per(II)‐mediated dehydration of the homoallylic amino alcohol. Protonation of the resultant cop‐ per(II)‐activated aminodiene is then thought to trigger subsequent intramolecular hydroamination to give the partially hydrogenated nitrogen heterocycle.