Mechanistic Issues in [2+2]- Photocycloadditions of Cyclic Enones to Alkenes

Corey and co-workers reported [2+2]- photocycloadditions of 2-cyclohexenone (CH) to a variety of alkenes,

and established many of the characteristic features of this reaction.

(72.1)

The potential of this type of reaction, as a key step in the synthesis of natural products, was first shown by Corey in his landmark synthesis of caryophyllene (Eq. (72.2)).