corresponding phosphate derivatives XIa–c and XVIIIa–c. The same compounds are obtained upon reacting VII and/or VIII with the proper dialkyl hydrogen phosphite. The trialkyl phosphites cause the quantitative reduction of perinaphthindantrione (IX) and/or its monohydrate (X) producing dihydroxy-peri-naphthindenone (XXI). On the other hand, dialkyl hydrogen phosphites add to IX (or X), yielding compounds