Comparative analysis of hydrogen bonding with participation of the nitrogen, oxygen and sulfur atoms in the 2(2′-heteroaryl)pyrroles and their trifluoroacetyl derivatives based on the 1H, 13C, 15N spectroscopy and DFT calculations

✍ Scribed by Andrei V. Afonin; Alexander V. Vashchenko; Igor A. Ushakov; Nadezhda V. Zorina; Elena Yu. Schmidt

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 153 KB
• Volume: 46
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2197

✦ Synopsis

Abstract

The NHċbondX (X = N,O,S) intramolecular hydrogen bond in the series of 2(2′‐heteroaryl)pyrroles and their trifluoroacetyl derivatives is examined by the ^1^H, ^13^C, ^15^N spectroscopy and density functional theory (DFT) calculations. The influence of the hydrogen bond on coupling and shielding constants is considered. It is shown that the NHċbondN intramolecular hydrogen bond causes a larger increase in the absolute size of the ^1^J(N,H) coupling constant and a larger deshielding of the bridge proton than the NHċbondO hydrogen bond. The effect of the NHċbondS interaction on the ^1^J(N,H) coupling constant and the shielding of the bridge proton is small. The NMR parameter changes in the series of the 2(2′‐heteroaryl)pyrroles due to NHċbondX hydrogen bond and the series of the 1‐vinyl‐2‐(2′‐heteroaryl)‐pyrroles due to CHċbondX hydrogen bond have the same order. The proximity of the nitrogen, oxygen or sulfur lone pair to the FċbondH hydrogen bridge quenches the trans‐hydrogen bond spin–spin couplings ^1h^J(F,H‐1) and ^2h^J(F,N). Copyright © 2008 John Wiley & Sons, Ltd.