Solution Chemistry of N,N’‐Disubstituted Amidines: Identification of Isomers and Evidence for Linear Dimer Formation
- 7 November 2016
- journal article
- research article
- Published by Wiley in Chemistry – A European Journal
- Vol. 22 (50) , 18190-18196
Abstract
Amidines have found widespread use, but their solution chemistry remains poorly understood. In this work, X‐ray crystallographic and detailed 1D and 2D NMR spectroscopic studies have been performed to elucidate the preferred isomers and their interconversion mechanisms. Amidines are shown to exist as a mixture of E‐syn and Z‐anti isomers in solution and to form dimeric H‐bonded aggregates that are also observed in the solid state. Rapid proton exchange/tautomerization reactions occur within the dimers, allowing fast interconversion of E‐syn and Z‐anti isomers even at very low temperatures. Three different exchange processes were identified in solution, and on this basis the unusual concentration and temperature dependence of the NMR spectra of these amidines could be explained. This work thus resolves some of the puzzles of the complex solution chemistry of this prominent class of compounds.Keywords
This publication has 49 references indexed in Scilit:
- N1,N2-DiphenylacetamidineActa Crystallographica Section C Crystal Structure Communications, 1997
- 1H, 13C and 15N nuclear magnetic resonance studies of polyamidines prepared from di(4,4′-aminophenyl) methane and different triethyl orthoesters—polymers with a prototropic tautomerismPolymer, 1997
- Application of infrared spectrometry to the study of tautomeric equilibria and hydrogen bonding basicity of medical and biochemical agents: N,N′-disubstituted amidinesThe Analyst, 1994
- Application of infrared spectrometry to the study of tautomerism and conformational and configurational isomerism in medical and biochemical agents: N,N′-disubstituted amidinesThe Analyst, 1992
- Dynamic NMR study of the kinetic HH/HD/DD isotope effects on the double proton transfer in cyclic bis(p-fluorophenyl)formamidine dimersThe Journal of Physical Chemistry, 1991
- N,N'-diphenylacetamidinium carboxylatesCollection of Czechoslovak Chemical Communications, 1990
- Solvent effect on the 13C and 15N NMR chemical shifts and rotational barriers in N,1N1‐dimethyl‐and N,1N1‐hexamethylene‐N2 ‐phenylformamidinesMagnetic Resonance in Chemistry, 1989
- 1H and 13C NMR study of hindered rotation in N1,N1‐dimethyl‐N2‐substituted phenylacetamidinesMagnetic Resonance in Chemistry, 1988
- Molecular structure of N,N?-diphenylformamidineJournal of Chemical Crystallography, 1987
- Amidines. XVII—substituent-induced chemical shifts in13C NMR spectra of N2-phenyl-formamidines, -acetamidines and -guanidinesMagnetic Resonance in Chemistry, 1986