Journal of the American Chemical Society, Vol.131, No.1, 54-54, 2009
Axially Chiral Binaphthyl Surrogates with an Inner N-H-N Hydrogen Bond
Novel chiral binaphtyl surrogates with an inner hydrogen bond have been created. The N H appears at 13.0-13.3 ppm in their H-1 NMR spectrum, indicating extremely strong hydrogen bonding. Enantiomers of these compounds were stable at ambient temperature and separable by HPLC with a chiral stationary phase. The half-lives of racemization of the enantiomer are in the range 3 months to 2 years at 20 degrees C, and the barriers for racemization are in the range 27.0 to 28.2 kcal/mol. An X-ray crystal analysis of the compound (R = CHPh2) shows that the pseudonaphthyl skeleton including C=N center dot center dot center dot H N is almost completely planar and the dihedral angle between the pseudonaphthalene and naphthalene rings is 128 degrees.