DMAP‐Catalyzed [4 + 2] Cycloaddition of α,β‐Unsaturated Carboxylic Acids with Ketones for Synthesis of α,β‐Unsaturated δ‐Lactones

The DMAP ‐catalyzed [4 + 2] cycloaddition of α , β ‐unsaturated carboxylic acids with ketones furnishing α , β ‐unsaturated δ ‐lactones in good yields (up to 80%) is described, which is the first example of remote γ ‐C(sp 3 )‐H activation of α , β ‐unsaturated carboxylic acids facilitated by DMAP , a pyridine‐based catalyst.