Terminating platinum-initiated cation-olefin reactions with simple alkenes.

The en masse cyclization of polyolefins into polycyclic terpenoids by cyclase enzymes (e.g. squalene to hopene), is a biosynthetic reaction of particular fascination to chemists. Noteworthy recent additions to synthetic mimics of the cyclase enzymes are asymmetric methods that include Brønsted–Lewis acids (BLA), masked equivalents of Br and I, organocatalysts, and electrophilic metal catalysts. With the exception of Hg reagents, few electrophilic metal catalysts cyclize polyenes with bio-like alkene terminators. The development of methods whose catalysts can initiate, cyclize, and terminate polyenes under ligand control would significantly advance the state of the art.