Studies on quinones. VIII. The application of michael adducts from 2-hydroxy-1,4-naphthoquinones for the preparation of dihydronaphthopyrandiones

Dihydronaphthopyran-5,10-diones 7,13, 16 and their corresponding dihydronaphthopyran-5,6-diones 8, 14,17 have been obtained starting from Michael adducts of 2-hydroxy- and 2-hydroxy-7-methoxy-1,4-naph-thoquinone ( 1, 9 ). An efficient synthesis of hydroxyhydrolapachol ( 4 ) employing 2-hydroxy-3-(3-oxobutyl)-1,4-naphthoquinone ( 5 ) is described.