Regioselective Oxidative Cation-Olefin Cyclization of Poly-enes: Catalyst Turnover via Hydride Abstraction

Electrophilic P 2 Pt 2+ complexes are shown to catalyze the regio- and diastereoselective oxidative cascade cyclization of poly-enes. The reactions are stereospecific with respect to the initiating alkenes geometry and suggest an all-chair, semiconcerted transition structure. Catalyst turnover after cyclization apparently occurs via β-hydride elimination and subsequent hydride abstraction (from P 2 Pt−H + ) by added Trityl cation (in the form of trityl methyl ether or a resin version thereof) to regenerate the active P 2 Pt 2+ state. One intriguing possibility is that the high regioselectivity observed in the β-H elimination is due to a regio-defining β-agostic resting state.