Reactivity of ubiquinones and ubiquinols with free radicals

The reactivity of quinones 1-4 and of the corresponding quinols 5-8 towards carbon- and oxygen-centred radicals were studied. Ali quinones bearing at least one nuclear position free, readily react with alkyl and phenyl radica ls to afford the alkylated quinones 12-24; however, quinones 1 and 3 reacte d with 2-cyano-2-propyl radical to yield products (the mono- and di-ethers 9-11) derived from the attack on the carbonylic oxygen. The reactions carri ed out on quinones with the benzoyloxy radical led to no reaction products and in the case of Q(10), the isoprenic chain also remained unchanged. Quin ols 5-8 reacted only with oxygen-centred radicals (benzoyloxy and 2-cyano-2 -propyl-peroxy radicals) to give the corresponding quinones. The isoprenic chain of Q(10) did not undergo attack even with peroxy radicals. Carbon-cen tred radicals resulted unable to abstract hydrogen from the studied quinols .