RADICAL-ION PROBES - 8 - DIRECT AND INDIRECT ELECTROCHEMISTRY OF 5,7-DI-TERT-BUTYLSPIRO[2.5]OCTA-4,7-DIEN-6-ONE AND DERIVATIVES

Results pertaining to the direct and indirect electrochemistry of 5, 7 -di-tert-butylspiro[2.5]octa-4, 7-dien-6-one (1a), 1-methyl-5, 7-di-te rt-butylspiro[2.5]octa-4, 7-dien-6-one (1b), and 1, 1,-dimethyl-5, 7-d i-tert-butylspiro[2.5]octa-4, 7-dien-6-one (1c) are reported. Product analyses reveal that reduction of all these substrates leads to cyclop ropane ring-opened products; ring opening occurs with modest selectivi ty leading to the more substituted (stable) distonic radical anion. Th e direct electrochemistry of these compounds is characterized by rate limiting electron transfer (with alpha approximate to 0.5), suggesting that while ring opening is extremely rapid, the radical anions do hav e a discrete lifetime (i.e., electron transfer and ring opening are no t concerted). Utilizing homogeneous redox catalysis, rate constants fo r electron transfer between la, Ib, and Ic and a series of aromatic ra dical anions were measured; reduction potentials and reorganization en ergies were derived from these rate constants by using Marcus theory.