Asymmetric Synthesis by Using Natural Sunlight under Absolute Achiral Conditions.

Irradiation of prochiral (E)-aroylacrylamide with sunlight gave single-handed pyrrolinone quantitatively and with an enantiomeric excess (ee) of over 99 % under absolutely achiral conditions. The phenomenon was explained by photoisomerization and reversible cyclization followed by dynamic crystallization involving deracemization.