Convenient synthesis of cyclopenta[c,d]pyrene and 3,4‐dihydrocyclopenta[c,d]pyrene. The reactivity of the pyrene dianion

Abstract The reactivity of the pyrene dianion has been investigated. Initial attack by electrophiles on the pyrene dianion has been shown to take place exclusively at the 4(9)‐position, leading to mono‐anions (11, 15) which can be converted into 9‐substituted 1,9‐dihydropyrene derivatives (12, 16). The latter can be rearranged to give the novel 4‐substituted 4,5‐dihydropyrene derivatives (13, 17), which provide access to 4‐substituted pyrene derivatives (14, 5). Cyclopenta[c,d]pyrene (1) and 3,4‐dihydrocyclopenta[c,d]pyrene (2), two widespread environmental contaminants, have been synthesized from pyrene in four (64%) and in five steps (62%), respectively, utilizing the chemical properties of the pyrene dianion. In these easy and straightforward syntheses the thus far unknown 4,5‐dihydro‐4‐pyreneacetic acid (17) plays a major role.