Concave Imidazolinium Salts as Precursors to Concave N-Heterocyclic Carbenes

✍ Scribed by Ole Winkelmann; Christian Näther; Ulrich Lüning

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 200 KB
• Volume: 2007
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200600843

✦ Synopsis

Abstract

Concave bimacrocyclic imidazolinium ions 8 have been synthesized as precursors for N‐heterocyclic carbenes 9 (NHC) in 13 to 29 % overall yields based on 2‐nitroresorcinol (1). As bridgeheads, 2,6‐bis(ω‐alkenyloxy)anilines 3 have been synthesized from 1. Reaction of 3 with oxalyl chloride, reduction to respective diamines 5, and ring closure with triethyl orthoformate gave N,N‐diaryl‐substituted imidazolinium ions 6. The terminal vinyl groups were connected by ring‐closing metathesis to give bimacrocyclic imidazolinium ions 7, whose alkene functions were hydrogenated to give saturated bimacrocyles 8. The structure of 8a was elucidated by X‐ray analysis. The respective NHC 9 was generated by deprotonation with potassium tert‐butoxide, and 9 was scavenged with CS~2~ to give adduct 10. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)