4- Hydroxycyclohexa-2,5-dien-l-ones

Reaction with p-benzoquinones.6 Fischer and Henderson have found conditions that result in 1,2-addition of various RLi reagents to p-benzoquinonc. The reaction when conducted in ether at —78° results in 4-alkyl-4-hydroxycyclohexa-2,5-diene-l-ones. These products undergo further 1,2-addition with RLi in THF to give dialkyl-cyclohexa-2,5-diene-l,4-diols. Mixed dienediols can be obtained by use of two different RLi reagents. 

When Nu is electron donating the product is as a rule more easily oxidized than the starting material, resulting in further oxidation under the reaction conditions and, frequently, complex reaction mixtures. The anodic methoxylation of naphthalene, which results in 1-methoxy-, 1,2-dimethoxy-, and 1,4-dimethoxynaphthalene, approximately in a 1 2 1 ratio, serves as an illustration of this problem [67]. However, in other cases, a single major product is obtained after a sequence of reactions, such as the oxidation of mesitylene in MeCN-diluted H2SO4 to 2,4,6-trimethyl-4-hydroxycyclohexa-2,5-dien-l-one in a substitution-elimination reaction [68] or the oxidation of anthracene in MeOH to 9,9,10,l0-tetramethoxy-9,10-dihydroanthracene in a substitution-addition reaction [Eq. (28)] [69]. 

The reaction of l,2-bis(diphenylphosphino)ethane with substimted o-benzoquinones affords bis(6-hydroxycyclohexa-2,4-dienone) derivatives. Treatment of the same reagent with o-naphthoquinone, phenanthrenequinone and acenaphthenequinone gave the respective bis(diphenylphosphoryl)ethylidenes or diacenaphthylenone derivatives. On the other hand, p-quinones react with l,2-bis(diphenylphosphino)methane to yield the corresponding 4-hydroxycyclohexa-2,5-dien-l-ones. ... 

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