Molecular tweezers for enantiodiscrimination in NMR: Di‐(R,R)‐1‐[10‐(1‐hydroxy‐2,2,2‐trifluoroethyl)‐9‐anthryl]‐2,2,2‐trifluoroethyl benzenedicarboxylates

Abstract

A series of new chiral molecular tweezers, di-(R,R)-1-[10-(1-hydroxy-2,2,2-trifluoroethyl)-9-anthryl]-2,2,2-trifluoroethyl phthalate (2), isophthalate (3) and terephthalate (4), were synthesized and their structure studied by NMR and molecular mechanics. Their effectiveness as chiral solvating agents for the determination of the enantiomeric purity of chiral compounds using NMR was demonstrated.

A New Chirally Organized Trifluoromethylanthrylmethanol Derivative and Its Application as Chiral Solvating Agent

“…The 1 H NMR spectra of both enantiopure diastereoisomers of 4 are shown in Figure b and 2c, which illustrate the very small differences in their chemical shifts. The complete assignation of all the proton signals of both (a S,R,R )‐ and (a R,R,R )‐ 4 was carried out assuming that the doublet at higher fields (δ 9.09 for (a S,R,R )‐ 4 ) corresponds to H‐1 proton due to the alcohol group influence, as we previously reported . This hypothesis was also confirmed performing a HOESY experiment.…”

Stereochemical vocabulary for structures that are chiral but not asymmetric: History, analysis, and proposal for a rational terminology

“…Beyond the theoretical and historical interest in chiral but not asymmetric molecules, however, today such molecules are used in a large variety of practical applications and appear in the literature with extremely high frequency. For example, in enantioselective or diastereoselective synthesis many such molecules are important as chiral building blocks, auxiliaries, ligands, or catalysts;22–30 some are used as resolving agents in resolutions of racemates via fractional crystallization of diastereoisomeric derivatives;31, 32 in chromatographic enantioseparations such molecules are important in a variety of roles including as analytes of theoretical interest,33 as selectors incorporated into chiral stationary phases,34 as pre‐chromatographic chiral derivatizing agents,35, 36 etc; some chiral but not asymmetric molecules are of considerable importance as chiral solvating agents in NMR;37, 38 some have been used as enantioselective extractants in liquid‐liquid extractions;39 others are of interest as pharmacologically active agents;40, 41 some have been used in other applications, for example, as components of polymers,42 as constituents of liquid crystals,43 in sonochemistry,44 etc. Many of these compounds belong to the C 2 point group.…”