Spiro (dibenxo [a, d] cgcloheptadiene-5~ 5'-hydantoin)(IIa), an analog of diphenylhydantoin, was prepared by the rearrangement, of dibenzo [a, e] cyclooctadiene-5, 6-dione (111) wit'h urea and alkali and by heating 5-hydroxy-dibenzo [a, d] cycloheptadiene-5-carboxplic acid (VII, R= H) with urea alone. Substitution of thiourea in the first, method gave the corresponding spirothiohydantoin (17) which was then converted to the desthio ...