NMR Chiral Solvating Agents

Determination of enantiomeric composition of (−)‐(R)‐2‐tert‐butyltetrahydroimidazolidin‐4‐one by polarimetry, 1H NMR, and chiral SFC

“…10 The ability of this fluoroalcohol to form diastereomeric complexes in solution with (R)-1 and (S)-1 is due to the acidity of hydrogen atoms bonded to oxygen and methine carbon of the trifluoroethanol moiety. The generally accepted dibasic model proposed by Professor Pirkle 10 and reported studies on bicyclic b-lactams 11 anticipate that interactions of hydroxyl and methine hydrogen atoms of S-TAE occur with carbonyl oxygen and amidic nitrogen of (R)-1 and (S)-1, respectively. The corresponding diastereomeric complexes (R)-1/S-TAE and (S)-1/S-TAE were built and analyzed with the CS Chem3D ProR program.…”

“…(+)-(S)-2,2,2-Trifluoro-1-(9-anthryl)-ethanol (S-TAE, 16 mg) was then added to the NMR tube, and the tube was shaken to dissolve all solid material and then inserted into the probe to measure the 1 H-NMR spectrum. 10 The single signals at 3.90 and 4.01 ppm (Fig. 2), which are attributed to enantiotopic hydrogen attached to C2 of the imidazolidinone moiety, were integrated four times, and the average integrations were used to calculate the ee values (ee = 100(I R À I S /I R + I S )) shown in Table 1.…”

Determination of Enantioselectivities by Means of Chiral Stationary Phase HPLC in Order to Identify Effective Proline-Derived Organocatalysts

“…Asymmetric synthesis makes use of different analytical techniques such as X-ray diffraction, 3 chiral nuclear magnetic resonance (NMR) shift reagents, 4 chiral chromatography, 5 among others, 6 with the aim of evaluating the efficiency of a given strategy, either via chiral auxiliaries, 7 asymmetric catalysis mediated by metal complexes, 8 enzymatic catalysis 9 and, a more recently developed methodology, organocatalysis. …”

NMR enantiodifferentiation of quaternary ammonium salts of Tröger base

“…[6][7][8][9][10][11][12][13] Lanthanide reagents, which are particularly efficient for most applications, have however been rarely used with such chiral cations due to often line broadening and distorted baselines. Previously, chiral hexacoordinated phosphate anion BINPHAT 1 (bis(tetrachlorobenzenediolato)mono([1,1 0 ]binaphthalenyl-2,2 0 -diolato)phosphate(v), Fig.…”