Synthesis of tetracyclic chromenones via platinum(II) chloride catalysed cascade cyclization of enediyne-enones

PtCl2 catalysed cascade cyclization of an enediyne-enone system to afford a tetracyclic chromenone is reported, which proceeds through two consecutive highly regioselective 6-endo-dig cyclizations in a single step with the formation of two new C-C bonds and two new rings in excellent yield. A mechanism for this transformation is proposed based on the isolated intermediates.