Urea derivatives based on a 1,1′-binaphthalene skeleton as chiral solvating agents for sulfoxides

Abstract

Five optically active urea derivatives 1–5 were synthesized via reaction of (R)-1,1′-binaphthalene-2,2′-diamine with the corresponding isocyanates. Analysis by 1H nuclear magnetic resonance spectroscopy demonstrated that 1 was the best chiral solvating agent for the determination of the enantiomeric excesses of various sulfoxides (13 examples). This compound was more efficient in terms of discriminating between enantiomers than the commercially available chiral solvating agent ((R)-(3,5-dinitro-benzoyl)-α-phenethylamine). Large non-equivalent chemical shifts (0.1ppm) can be achieved, especially with aliphatic sulfoxides.