Synthesis and Applications of Cyclohexenyl Halides Obtained by a Cationic Carbocyclisation Reaction

The synthesis of cyclic alkenyl halides (mainly fluorides, chlorides and bromides) from alkynol or enyne derivatives by an acid‐mediated cationic cyclisation reaction is disclosed. This high‐yielding, scalable and technically simple method complements and challenges conventional methodologies. This study includes the development of biomimetic cationic cyclisation reactions of polyenyne derivatives to give interesting halogen‐containing polycyclic compounds. The application of this reaction in the key step of the synthesis of two terpenes, namely austrodoral and pallescensin A, and the potent odorant 9‐epi‐Ambrox demonstrates the potential of the reaction for natural product synthesis. It's all under regio‐control! Cyclic alkenyl fluorides, chlorides, bromides and iodides are readily obtained by a cationic cyclisation process. Related biomimetic polycyclisation reactions allow the synthesis of interesting polycyclic core skeletons that may be used in the context of natural product synthesis (see scheme).