Tetraphenylcyclopentadienone
Chemical compound
From Wikipedia, the free encyclopedia
Tetraphenylcyclopentadienone is an organic compound with the formula (C6H5C)4C4C=O. It is classified as a cyclic dienone. It is a dark purple to black crystalline solid that is soluble in organic solvents. It is an easily made building block for many organic and organometallic compounds. It can be synthesized by a double aldol condensation involving benzil and dibenzyl ketone.
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 Perspective view, showing the canted phenyl rings[1] | |
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| Names | |
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| Preferred IUPAC name
2,3,4,5-Tetraphenylcyclopenta-2,4-dien-1-one | |
| Other names
Tetracyclone, TPCPD, Cyclone | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.006.847 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C29H20O | |
| Molar mass | 384.478 g·mol−1 |
| Appearance | black solid |
| Melting point | 219 to 220 °C (426 to 428 °F; 492 to 493 K)[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[1] The phenyl groups of tetraphenylcyclopentadienone adopt a "propeller" shape in its 3D conformation. The four phenyl rings are rotated out of the plane of the central ring because of steric repulsion with each other.[3]
Unlike the parent compound cyclopentadienone, which rapidly dimerizes,[4] 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.[2][5]
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.[5] In this way, it is a precursor to graphene-like molecules,[6] such as coronene.
Similarly, pentaphenylpyridine derivatives may be prepared via a Diels–Alder reaction between tetraphenylcyclopentadienone and benzonitrile.[7]
Tetraphenylcyclopentadienone can provide an effective alternative to DDQ in aromatization of porphyrins:[8]
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.[9]