Platinum-Catalyzed Cascade Synthesis of Indoloquinazolinones

Significance

Reported is a one-pot platinum(IV) iodide dihydroxylation-cyclization synthesis of ­indoloquinazolinones. A plausible mechanism is proposed and is consistent with the rational for performing the cascade. The first step is the coordination of platinum to the alkyne for activating it towards the nucleophilic attack by the N-alkoxy­amide to form the six-membered ring. Formation of a platinum carbenoid facilitates the ejection of hydroxide to give an iminium species. Insertion of the ortho C-H bond into the platinum carbenoid generates the five-membered ring, which after a proton transfer yields the final product.