Abstract: The synthesis of 4, 8-dihydrodibenzo [cd, gh] pentalene from 4, 5- methylenephenanthrene is reported. The key step involves a ring contraction qf the diazo ketone from 4, 5-methylene-9, 1O-phenanthraquinone which is complicated by an un-usual addition of the intermediate ketocarbene to the aromatic solvent. This dihydrodibenzopentalene derivative serves as the precursor of three derivatives of ...
