Synthesis and Vibrational Circular Dichroism Analysis of N-Heterocyclic Carbene Precursors Containing Remote Chirality Centers

International Journal of Molecular Sciences

Tibor Kovács¹  Tibor Kurtán¹  Attila Mándi¹  Attila Paczal²  Zita Szabó²  Andras Kotschy² 

[1]Department of Organic Chemistry, University of Debrecen, P.O. Box 400, 4002 Debrecen, Hungary

[2]Servier Research Institute of Medicinal Chemistry, Záhony u. 7., 1031 Budapest, Hungary

关键词: DFT calculations;    characteristic VCD transitions;    electronic circular dichroism;    conformational analysis;    NHC precursors;   

DOI  :  10.3390/ijms23073471

来源: DOAJ

【 摘 要 】

VCD analysis of 16 diastereomeric pairs of NHC precursors containing two isolated chirality centers and different substitution patterns identified VCD transitions characteristic of the chirality center in the imidazolium ring or in the side chain, which, in contrast to ECD and OR, could be utilized to assign the two chirality centers separately by simple comparison, regardless of the type and position of achiral aromatic substituents. While the ECD and OR data showed great dependence on the position of an achiral substituent such as a methoxy group, characteristic experimental VCD transitions remained consistent and they could be used to determine the absolute configuration of all the regio- and stereoisomers and substituted analogues. VCD, ECD and OR approaches were evaluated, and several carbene precursors were found, for which only the VCD method could distinguish the four stereoisomers. With t-butyl, phenyl or 2-naphthyl substituents at the C-1′ chirality center, the ECD spectra of the C-1′ epimers were near-identical, and hence it was only the VCD approach that showed distinct differences suitable for the configurational assignment. The chiroptical characterization of our diastereomeric pairs of NHC precursors enables the future application of related derivatives having different substitution patterns in stereoselective transformations.

【 授权许可】

Unknown