Self-association promoted conformational transition of (3R,4S,8R,9R)-9-[(3,5-bis(trifluoromethyl)phenyl))-thiourea](9-deoxy)-epi-cinchonine.
The conformational diversity of the (3R,4S,8R,9R)-9-[(3,5-bis(trifluoromethyl)phenyl))-thiourea](9-deoxy)-epi-cinchonine organocatalyst is discussed. Low-temperature NMR experiments confirmed a self-association process, which promotes the quinoline rotation between two intramolecularly hydrogen-bonded monomeric conformers of the catalyst. The balanced population of the coexisting monomeric and dimeric species allowed us to conduct a structural study of a rather complex conformational dynamics of the pure catalyst. The study is extended by a comparison with other members of the bifunctional amine-thiourea organocatalyst family. Changes in the molecular structure of the catalysts influence the interplay between intra- and intermolecular hydrogen bonding, and yield different extent of catalyst self-association. By assessing the conformation of the individual states, we established the thermodynamic model of a self-association promoted conformational transition.
Laboratory for NMR Spectroscopy, Institute of Structural Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, Pusztaszeri út 59-67, H-1025 Budapest, Hungary.
Péter
P
Király
Tibor
T
Soós
Szilárd
S
Varga
Benedek
B
Vakulya
Gábor
G
Tárkányi
D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D015394:Molecular Structure; D011804:Quinolines / Q000737:chemistry; D013816:Thermodynamics
C547439:(3R,4S,8R,9R)-9-((3,5-bis(trifluoromethyl)phenyl)-thiourea)(9-deoxy)-epi-cinchonine; D002930:Cinchona Alkaloids; D011804:Quinolines; C037219:quinoline; C010086:cinchonine