Determination of the absolute stereostructure of a cyclic azobenzene from the crystal structure of the precursor containing a heavy element.
Single crystal X-ray diffraction has been used as one of the common methods for the unambiguous determination of the absolute stereostructure of chiral molecules. However, this method is limited to molecules containing heavy atoms or to molecules with the possibility of functionalization with heavy elements or chiral internal references. Herein, we report the determination of the absolute stereostructure of the enantiomers of molecule (E)-2, which lacks the possibility of functionalization, using a reverse method, i.e., defunctionalization of its precursor of known stereostructure with bromine substitution (S-(-)-(E)-1). A reductive debromination ofS-(-)-(E)-1results in formation of one of the enantiomers of (E)-2. Using a combination of HPLC and CD spectroscopy we could safely assign the stereostructure of one of the enantiomers of (E)-2, the reduced productR-(-)-(E)-1.
Research Institute for Electronic for Science, Hokkaido University, Kita-ku, N 20, W 10, Sapporo-001-0020, Japan; Postgraduate and Research Department of Chemistry, Farook College, Farook College P. O., Kozhikode, 673632, Kerala, India.
Reji
R
Thomas
Research Institute for Electronic for Science, Hokkaido University, Kita-ku, N 20, W 10, Sapporo-001-0020, Japan.
Nobuyuki
N
Tamaoki
X-ray crystal analysis; azobenzene; cyclic compound; enantiomer; stereostructure