Cationic Iron(III) Salt as an Initiator for Radical Cation-induced [4+2] Cycloaddition

We developed a cationic iron(III) salt initiator for radical cation-induced [4+2] cycloaddition. Fe(OTf)(3) [or Fe(ClO4)(3)] behaves as a highly active oxidant for both electron-deficient and electron-rich dienophiles. The scope of substrates is much broader than with FeCl3 reported previously. With highly active Fe(OTf)(3), we demonstrate a formal total synthesis of Heitziamide A.