Nucleophilic Substitution of 4H-Imidazoles - A Key Step in the Synthesis of Fused Imidazoles and New Chromophores

✍ Scribed by Jens Atzrodt; Rainer Beckert; Wolfgang Günther; Helmar Görls

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 295 KB
• Volume: 2000
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/(sici)1099-0690(200004)2000:8<1661::aid-ejoc1661>3.0.co;2-1

✦ Synopsis

The electrophilic properties of the 4H-imidazoles 1 and their protonated derivatives 2 permit the introduction of nucleophilic building blocks, as illustrated by reactions of 1 with selected amines. Depending on the nature of the amine and the substituents R 1 on the heterocycle 1, single (3) or double (4) transamination is observed. The 1 H-NMR spectra of the products, as well as X-ray structure analyses of compounds 3f and 4c, confirm that the residues at the 4-and/or 5-positions of 1 are exchanged. The tautomerism between 3e-h and 3eЈ-hЈ seems to be central to the chemistry of these mixed substituted derivatives. Using orthoesters and acetophenone dimethylacetal as cyclization partners, the imid-