Quinones and quinone methides—V: Further rearrangements of the dimer from 5-methoxy-2-(4-methoxyphenylmethyl)-1,4-benzoquinone

In strongly acid solutions the dimer 3 dissociates to the quinone 1 and quinone methide 2 which recombine with elimination of p-methoxybenzyl alcohol to form the xanthylium salt 9a. With zinc and acetic acid 3 yields isormeric meso- and dl-ethylenediquinol derivatives 14a. Sodium borohydride reduction of 3 yields an alcoholic quinol 5a which rapidly reoxidizes to the spiro-tetrahydrofuran derivative 24a. Possible mechanisms which may be involved in the formation of these rearranged products are discussed.