Tetraphenylcyclopentadienone

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.

Tetraphenylcyclopentadienone

Perspective view, showing the canted phenyl rings[1]
Names
Preferred IUPAC name 2,3,4,5-Tetraphenylcyclopenta-2,4-dien-1-one
Other names Tetracyclone, TPCPD, Cyclone
Identifiers
CAS Number	479-33-4 Y
3D model (JSmol)	Interactive image
ChemSpider	61382 Y
ECHA InfoCard	100.006.847
PubChem CID	68068
UNII	E8CT23P8WP Y
CompTox Dashboard (EPA)	DTXSID1060059
InChI InChI=1S/C29H20O/c30-29-27(23-17-9-3-10-18-23)25(21-13-5-1-6-14-21)26(22-15-7-2-8-16-22)28(29)24-19-11-4-12-20-24/h1-20H Y Key: PLGPSDNOLCVGSS-UHFFFAOYSA-N Y InChI=1/C29H20O/c30-29-27(23-17-9-3-10-18-23)25(21-13-5-1-6-14-21)26(22-15-7-2-8-16-22)28(29)24-19-11-4-12-20-24/h1-20H Key: PLGPSDNOLCVGSS-UHFFFAOYAO
SMILES O=C2C(=C(/C(=C2/c1ccccc1)c3ccccc3)c4ccccc4)\c5ccccc5
Properties
Chemical formula	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). Y verify (what is YN ?) Infobox references

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

The Shvo catalyst is a ruthenium complex of tetraphenylcyclopentadienone

Tetraarylcyclopentadienones are a well studied class of ligands in organometallic chemistry. The Shvo catalyst, useful for certain hydrogenations, is derived from tetraphenylcyclopentadienone.^[9]