(Scheme 58).
74
Analogously to the arguments put
forward in the Diels-Alder reaction of175(Scheme
52), (Z)-alkenes such as193consistently gave better
selectivities compared to (E)-alkenes. Nevertheless,
some (E)-alkenes such as196also displayed surpris-ingly highanti-Felkin selectivity, although 1,3-allylic
strain should not be a decisive factor any longer in
such cases.