Diphenylketene

The most important reaction of diphenyl ketene is the [2+2] cycloaddition at C-C, C-N, C-O, and C-S multiple bonds.

[3] The first synthesis by H. Staudinger was based on 2-chlorodiphenylacetyl chloride (prepared from benzilic acid and thionyl chloride[4]) from which two chlorine atoms are cleaved with zinc in a dehalogenation reaction:[2] An early synthesis uses benzilmonohydrazone (from Diphenylethanedione and hydrazine hydrate[5]), which is oxidized with mercury(II)oxide and calcium sulfate to form mono-diazoketone, and is then converted into the diphenylketene at 100 °C under nitrogen elimination in 58% yield:[6] A further early diphenylketene synthesis originates from Eduard Wedekind, who had already obtained diphenyl ketene in 1901 by the dehydrohalogenation of diphenylacetyl chloride with triethylamine, without isolation and characterization though.

[10] Recently, a synthesis of diphenyl ketene from diphenylacetic acid and the Hendrickson reagent (triphenylphosphonium anhydride-trifluoromethanesulfonate)[11] with water elimination in 72% yield has been reported.

[12] Diphenyl ketene is at room temperature an orange-colored to red oil (with the color of concentrated potassium dichromate solution[2]) which is miscible with nonpolar organic solvents (such as diethyl ether, acetone, benzene, tetrahydrofuran, chloroform)[13] and solidifies in the cold forming yellow crystals.

[2] The compound is easily oxidized by air but can be stored in tightly closed containers at 0 °C for several weeks without decomposition[9] or in a nitrogen atmosphere with the addition of a small amount of hydroquinone as a polymerization inhibitor.

[6] Diphenylketene can undergo attack from a host of nucleophiles, including alcohols, amines, and enolates with fairly slow rates.

Skeletal formula
Ball-and-stick model
Syntheis of diphenylketene by Staudinger
Syntheis of diphenylketene by Staudinger
Synthesis of diphenylketene from benzilmonohydrazone
Synthesis of diphenylketene from benzilmonohydrazone
Synthesis of diphenylketene from diphenylacetate
Synthesis of diphenylketene from diphenylacetate
Synthesis of diphenylketene by debromination
Synthesis of diphenylketene by debromination
Synthesis of diphenylketene using the Hendrickson reagent
Synthesis of diphenylketene using the Hendrickson reagent
Dimers of diphenylketene
Dimers of diphenylketene
Autoxidation and polymerisation of diphenylketene
Autoxidation and polymerisation of diphenylketene
Formation of tetraphenylallene from diphenylketene
Formation of tetraphenylallene from diphenylketene
Addition of diphenylketen to cyclopentadiene
Addition of diphenylketen to cyclopentadiene
β-lactam formation from diphenylketene
β-lactam formation from diphenylketene
Cycloaddition of diphenylketene to diphenylnaphthol
Cycloaddition of diphenylketene to diphenylnaphthol