Synthesis and structure of sterically hindered o-benzoquinone carboxylic acid

2,4-Di-tert-butyl-5,6-dioxocyclohexa-1,3-diene-1-carboxylic acid, an oxidized analogue of sterically hindered pyrocatechuic acid, was obtained from 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde in four stages. The electrochemical reduction of this compound proceeds in two stages: the first reduction wave (E_red1=−0.24V) is irreversible, while the second stage is partially reversible (E_{1/2, red2}=−0.65V). The molecular structure of the o-quinone carboxylic acid in the crystalline state was comfirmed by single-crystal X-ray analysis.