Tetraphenylcyclopentadienone

Structure

The C5O core of the molecule is planar and conjugated, but the bonds have a definite alternating single- and double-bond nature. The C2–C3 and C4–C5 distances are 1.35 Å, while the C1–C2, C3–C4, C5–C1 are closer to single bonds with distances near 1.50 Å.

Unlike the parent compound cyclopentadienone, which rapidly dimerizes, the tetraphenyl derivative is isolable at room temperature.

Synthesis

Tetraphenylcyclopentadienone can be synthesized by a double aldol condensation involving benzil and dibenzyl ketone in the presence of a basic catalyst. :[[Image:Synthesis_of_tetraphenylcyclopentadienone.png|600px]]

Reactions

The central ring can serve as a diene in Diels–Alder reactions with various dienophiles. For example, reaction with benzyne leads to 1,2,3,4-tetraphenylnaphthalene and reaction with diphenylacetylene leads to hexaphenylbenzene. In this way, it is a precursor to graphene-like molecules, such as coronene.

Similarly, pentaphenylpyridine derivatives may be prepared via a Diels–Alder reaction between tetraphenylcyclopentadienone and benzonitrile.

Tetraphenylcyclopentadienone can provide an effective alternative to DDQ in aromatization of porphyrins:

Ligand in organometallic chemistry

Tetraarylcyclopentadienones are a well studied class of ligands in organometallic chemistry. The Shvo catalyst, useful for certain hydrogenations, is derived from tetraphenylcyclopentadienone.

References

References

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