PRODUCTS OF THE REACTIONS BETWEEN SUBSTITUTED ANTHRACENE RADICAL CATIONS AND NITROGEN-CENTERED NUCLEOPHILES

Radical cations derived from anthracene and 9-substituted or 9,10-disubstituted anthracenes react with pyridine and substituted pyridines in aprotic solvents to give either mono- or bis-pyridinium salts. Bis-pyridinium salts were observed when R1 = R2 = H. 9-Substituted anthracene radical cations (R1 = Ph, NO2, or CN and R2 = H) react to give mono-pyridinium salts, eqn. (i). The most important factors influencing [GRAPHICS] the product distribution are the steric environment at the 9-position after the initial attack by the nucleophile at the 10-position and the electronic effect of substituents at the latter position of the anthracene nucleus. In the case of the parent anthracene radical cation, attack at the 10-position leaves an unsubstituted 9-position for further attack resulting in the eventual formation of the bis-pyridinium salt. On the other hand, radical cations derived from 9-substituted anthracenes led to intermediates in which the 9-position is hindered toward nucleophilic attack and an acid-base reaction leading to mono-pyridinium salt prevails.