Improved synthesis of 1,4-phenanthrenequinones from Diels-Alder cycloadditions of 2-(p-Tolylsulfinyl)-1,4-benzoquinone
A wide range of substituted 1,4-phenanthrenequinones 5a-g and benz[c]- and benz[a]-1,4-phenanthrenequinones (5h) and (5i) were synthezised in one step through Diels-Alder cycloadditions of 2-(p-tolylsulfinyl)-1,4-benzoquinone 2 and vinylaromatic derivatives 1a-i under thermal and high pressure conditions in moderate to good yields (33-80%).