[Arylméthylène thiocétones chirales. Structure du 3-(o-méthoxyphényl)méthylène thiocamphre]

Arylmethylene thiocamphors are easily obtained from corresponding (+)-arylmethylene camphors by reaction with Lawesson reagent or P4S10. Crystals of o-methoxyphenylmethylene thiocamphor C18H22OS belong to space-group P2(1)2(1)2(1) with a = 7.581(9) Angstrom, b = 12.884(7) Angstrom and c = 16.831(7) Angstrom, Z = 4, T = 293 K. The final R is 0.055 for 1300 unique reflections. The cohesion of the crystal is the result of van der Waals interactions. This compound and all arylmethylene thiocamphors adopt the E configuration, more stable from the stereochemical point of view. The conjugated S=C-C=C system is skewed in the sense of a left handed helix. Furthermore, the aromatic ring is twisted (-32 degrees). Exciton Circular Dichroism is consistent with this conformation.