Ni-catalyzed unnatural prenylation and cyclic monoterpenation of heteroarenes with isoprene

Abstract

Terpenoids, such as hemiterpenoids and monoterpenoids, are the largest class of natural products, which widely exist in plants and marine organisms. Herein, a divergent strategy is developed for the introduction of unnatural prenyl and cyclic monoterpene skeleton through relay catalysis from basic feedstock isoprene. In the presence of catalytic amount of base, the unnatural prenylation of heteroarenes proceeds through Markovnikov addition onto isoprene with less hindered NHC (IMes) ligand under Ni catalysis. With the aid of extra base, a further in situ isomerization of Markovnikov addition products delivered unnatural hemiterpenoids with tetrasubstituted alkene motif in high selectivities. It was found that bulky NHC (IPr) ligand could further promote sequential hydroheteroarylation between isoprene dimers and heterocycles and gave monoterpenoids in one pot. This work provides a new strategy for regulating the synthesis of hemiterpenoids and monoterpenoids.