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.