The Diels-Alder reactions of methoxy-p-benzoquinone and 2,6-dimethoxy-p-benzoquinone, which may be obtained from lignin and lignin model compounds, and ofo-quinones (4-methyl, 4-acetyl, and 4-(l-hydroxyethyl)-o-benzoquinone) were investigated using 2,3-dimethylbutadiene, isoprene and styrene as dienes. Dimethylbutadiene and isoprene were found to be effective reactants, resulting in the generation of several Diels-Alder addition products. Loss of the methoxyl group and the side chain were observed under certain conditions. Reactions of thep-benzoquinones went more smoothly than the reactions of theo-quinones, and product yields were generally higher. Higher yields of anthraquinone products were obtained from 2,6-dimethoxy-p-benzoquinone than from methoxy-p-benzoquinone.
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