Absolute Helical Arrangement of Sulfonamide in the Crystal

1,2-Bis(N-benzenesulfonyl-N-methylamino)benzene (2), which has no fixed asymmetric element, was crystallized from ethyl acetate as chiral
crystals belonging to space group P41212 (No. 92) or P43212 (No. 96). The array of molecules built by the CH−π interaction along the c-axis
forms an enantiomeric helical superstructure in each individual crystal. The absolute configurations of the chiral crystals of 2 were determined
by X-ray crystal structure analysis using the Flack parameter method. The solid-state CD spectra of the chiral crystals in KBr were mirror
images. The equilibrium between the two enantiomers in solution is fast during crystallization at ambient temperature, and the energy barrier
(ΔG⧧) is estimated to be 11.7 ± 0.3 kcal/mol (233 K).