The [3+2]-cycloaddition reaction between
acrolein and in situ generated acyclic azomethine ylides
promoted by a chiral secondary amine to generate C-3
unsubstituted pyrrolidines has been studied in detail.
Optimum conditions involve the use of the cheap and
readily available l-Proline as catalyst to afford the
pyrrolidine cycloadduct with complete diastereomeric
control and up to 80% enantiomeric control.