Chiral Cyclopropenyl Ketones: Reactive and Selective Diels–Alder Dienophiles

The
synthesis and Diels–Alder reactions of cyclopropenyl
ketones are described. Cyclopropenyl ketones are highly reactive dienophiles
that can engage a range of cyclic dienes and 2,3-dimethylbutadiene.
The strategy of using cyclopropenyl ketones to facilitate Diels–Alder
reactions is not limited to products that contain three-membered rings,
as reductive opening by SmI2 can be used to produce a product
that lacks a cyclopropane but retains a quaternary stereogenic center.