Studies on the Mechanism of Base-Catalyzed Decomposition of Bicyclic Endoperoxides

Kornblum and Delamare showed the first decomposition of dialkyl peroxides by base-catalyzed rearrangement. They reported that 1-[1-(tert -butylperoxy)ethyl] benzene 1 gives acetophenone and tert-butanol by treatment with bases such as KOH, NaOEt, and piperidine. Milas and Surgenor reported previously the stability of 2-(tert -butylperoxy)-2-methylpropane against strong bases. Kornblum and Delamare proposed a three-step mechanism for the base-catalyzed decomposition of 1-[1-(tert -butylperoxy)ethyl]benzene (1) as outlined in Scheme 1. The first step of the reaction includes an abstraction of the α-proton to give an intermediate carbanion 2. In the second step the electron pair of the carbanion 2 displaces tert -butoxide to form a ketone (acetophenone). These steps presumably are synchronous. Finally, in the third step tert -butoxide captures the proton from the base to give tert -butanol. In view of this mechanism, only those dialkylperoxides and alkyl hydroperoxides having an α-proton next to the peroxide linkage should undergo base-catalyzed rearrangement. ∗Corresponding authors