On the Absolute Configuration of Chiral 1,4-Dihydropyridazines Synthesized by Organocatalysed Reactions

Abstract

A computational investigation of the specific optical rotation and of the electronic circular dichroism spectra of two chiral 1,4-dihydropyridazines was performed and compared with existing experimental data to verify a previous assignment of their absolute configuration based on a well-accepted mechanism of catalysis of the organocatalyst used in their synthesis. Both the optical rotation and circular dichroism calculations indicate that the absolute configuration is opposite to the one assigned on the basis of the mechanism originally assumed. An alternative reaction mechanism is therefore suggested.

Synthesis, Enzymatic Resolution, and Stereochemical Characterization of Isoparaconic Acid Derivatives: A Combined Experimental and Theoretical Investigation

“…Nowadays, computational analyses of chiroptical spectroscopies, optical rotation (OR), optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) can allow accurate structural analysis and a safe AC determination of chiral nonracemic molecules . More recently, this task has been performed mainly by the concerted use of these techniques .…”

“…Nowadays, computational analyses of chiroptical spectroscopies, [23][24][25] optical rotation (OR), optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) [26][27][28][29] can allow accurate structural analysis and a safe AC determination of chiral nonracemic molecules. 30 More recently, this task has been performed mainly by the concerted use of these techniques. [31][32][33][34] Therefore, thanks to all these powerful tools, the problem of AC determination of organic molecules looks now near to its ultimate solution.…”

Probing Molecular Chirality of Ground and Electronically Excited States in the UV-vis and X-ray Regimes: An EOM-CCSD Study

“…12,13 Indeed, experimental measurements of optical activity alone are not sufficient to establish the absolute configuration, since there is no direct correspondence between the enantiomer's configuration and the measured sign of the chiroptical property. However, if the simulated spectrum of the chosen configuration matches the sign pattern of the measured spectrum, one can conclude that the experimental sample contains the same enantiomer as in the simulation, 5,[12][13][14] provided, of course, that the computational method is reliable.…”

Probing Molecular Chirality of Ground and Electronically Excited States in the UV–vis and X-ray Regimes: An EOM-CCSD Study

“…The key step in contemporary use of spectroscopy for chiral discrimination is the simulation of the spectra for an a priori chosen absolute configuration of the chiral species. , Indeed, experimental measurements of optical activity alone are not sufficient to establish the absolute configuration, since there is no direct correspondence between the enantiomer’s configuration and the measured sign of the chiroptical property. However, if the simulated spectrum of the chosen configuration matches the sign pattern of the measured spectrum, one can conclude that the experimental sample contains the same enantiomer as in the simulation, ,− provided, of course, that the computational method is reliable.…”