Synthesis and Structures of Polyphenylphenanthrenes

1,2,3,4,5,6,7,8‐Octaphenylphenanthrene (4) and decaphenylphenanthrene (5) were prepared by very short syntheses (two or three steps) from tetraphenylfuran and polybrominated benzene derivatives. The X‐ray structures of compounds 4 and 5 show them to be quite crowded, with the phenanthrene cores twisted by about 40° due to the clash of the C4 and C5 phenyl groups. Compound 4 was resolved by chromatography on a chiral support, and its free energy of activation for racemization was determined to be 24.6 kcal mol−1 at 40 °C. Computational studies indicate that compound 5 has a racemization barrier approximately 6 kcal mol−1 lower than 4, and thus 5 would not be configurationally stable at room temperature. Crowded, chiral, twisted! 1,2,3,4,5,6,7,8‐Octaphenylphenanthrene and decaphenylphenanthrene were prepared by very short syntheses from tetraphenylfuran and polybrominated benzene derivatives. Their X‐ray structures show them to be crowded, chiral molecules, with the phenanthrene cores twisted by about 40° due to the clash of the C4 and C5 phenyl groups.