Access to [6-7-6]-Icetexanes through Sequential Cascade Cyclization and Biomimetic Ring Expansion

We herein report an efficient synthetic method for preparing [6-7-6]-icetexane derivatives. This approach employs our previously designed copper-catalyzed intramolecular cyclization of enyne-aryl carbonyl substrates to generate a [6-6-6]-tricyclic abietane framework and a subsequent ring expansion protocol for the [6-7-6] scaffold. By synergizing these protocols, we established a highly efficient pathway for synthesizing icetexane compounds from readily available enyne-aryl starting materials, exhibiting remarkable versatility in accommodating various functional groups while delivering consistently high yields. A synthetic approach to [6-7-6]-icetexane derivatives involving the cationic ring expansion of the [6-6-6]-tricyclic abietane core has been developed. This methodology enables the synthesis of [6-7-6]-icetexane compounds bearing diverse functional groups from aryl carbonyl substrates in high yields.+image