Absolute asymmetric β-lactam synthesis via the solid-state photoreaction of acyclic monothioimides and the reaction trajectory in the chiral crystalline environment

Achiral N-methacryloylthiobenzanilide formed (Z,E)-conformation of the imide moiety and crystallized in a chiral fashion. The solid-state photoreaction gave optically active β-lactam. The dynamic molecular rearrangement for cyclization was elucidated on the basis of direct comparison of the absolute configuration of both the starting material and the photoproduct. Crystal-to-crystal transformation was observed in the photoreaction of the (E,E)-conformation of N-isopropyl-N-tigloylthiobenzamide, which needs small atomic rearrangement for the cyclization and gave thietane stereo- and chemo-selectively.