A Chiral Acrylate Equivalent for Metal-Free Diels−Alder Reactions: <i>endo</i>-2-Acryloylisoborneol

The principle of metal-free activation of enones toward the Diels−Alder reaction with dienes is demonstrated by exploiting the capability of Brønsted acids to activate α‘-hydroxyenones through hydrogen bonding. The diastereoselective application of such a principle is nicely realized by using a newly designed family of camphor-based chiral enones, which upon catalytic action of either trifluoroacetic or triflic acid lead to the corresponding cycloadducts with high chemical and stereochemical efficiency.