Iron-Catalyzed Intramolecular Perezone-Type [5 + 2] Cycloaddition: Access to Tricyclo[6.3.1.0]dodecane.

An iron-catalyzed perezone-type [5 + 2] cycloaddition toward tricyclo[6.3.1.0]dodecane scaffolds is presented, furnishing cycloadducts with two new C-C bonds and three to four stereogenic centers generated with typically good yields and excellent diastereoselectivities. Two independent conditions, catalytic FeCl/PhCO tBu (0.5 equiv/1 equiv) and stoichiometric FeCl(2 equiv), have been respectively manifested to be applicable for various substrates. Mechanistically, the reaction may proceed via iron-mediated generation of a carbon cationic center, which triggers subsequent [5 + 2] cyclization. Derivation of the cycloadduct was conducted to testify the applicability of this method.