Org. Synth. 1960, 40, 85
Submitted by Tod W. Campbell and Richard N. McDonald1
Checked by Virgil Boekelheide and Richard E. Partch.
A. p-Xylylene-bis(triphenylphosphonium chloride). A mixture of 262 g. (1.0 mole) of triphenylphosphine (Note 1) and 84 g. (0.48 mole) of p-xylylene dichloride (Note 2) in 1 l. of dimethyl formamide is heated at reflux with stirring for 3 hours (Note 3). The mixture is then allowed to cool to room temperature with stirring, and the white crystalline solid is collected, washed with 100 ml. of dimethylformamide followed by 300 ml. of ether, and dried in a vacuum oven at 20 mm. pressure and 80°. The dry weight is 313–329 g. (93–98%).
B. 1,4-Bis-(4-phenylbutadienyl)benzene. To a solution of 70 g. (0.10 mole) of p-xylylene-bis(triphenylphosphonium chloride) and 35 g. (0.26 mole) of cinnamaldehyde in 250 ml. of ethanol (Note 4) is added a solution of 0.25M lithium ethoxide in ethanol (Note 5). After being allowed to stand overnight at room temperature the yellow solid is collected by filtration, washed with 300 ml. of 60% ethanol, and dried in a vacuum oven at 20 mm. and 70°. The dry weight is 29–32 g. (87–95%). The solid is then dissolved in the minimum amount (about 2 1.) of boiling xylene, treated with decolorizing charcoal, and filtered. The filtrate is reduced in volume to about 1.2 1. and digested at the boiling point with a trace of iodine for 3 hours (Note 6). After the solution has stood overnight at room temperature, the yellow plates are collected by filtration, washed with benzene, and dried in a vacuum oven at 20 mm. pressure at 70°. The weight of crystals, m.p. 285–287° (Note 7), is 23–25 g. (69–75%).
. A mixture of 3.40 g. (0.020 mole) of diethyl acetylenedicarboxylate2
and 3.34 g. (0.010 mole) of 1,4-bis-(4-phenylbutadienyl)benzene
is refluxed with 20 ml. of o-dichlorobenzene
for 3 hours. It is allowed to cool to about 80°, then 100 ml. of ethanol
and 5 g. of potassium hydroxide
are added, and the mixture is refluxed for about 2 hours. The solvent is evaporated on a steam bath
under a nitrogen
atmosphere (Note 8)
, and the damp solid is extracted with 200 ml. of water. The intense yellow or yellow-orange aqueous layer is filtered, then extracted twice with 75-ml. portions of ether
, charcoal is added and then filtered to separate water-insoluble matter. The filtrate is just neutralized with dilute hydrochloric acid (Note 9)
and then made basic with 5 g. of sodium carbonate
. To this is added a solution of 30 g. of potassium ferricyanide
in 200 ml. of water. The mixture rapidly becomes milky and is allowed to stand overnight (Note 10)
. The suspended solid is centrifuged and washed with water twice by centrifugation. It is dried in a vacuum oven to give 3.1–4.2 g.
of a green-tinged solid (Note 11)
. The combined material from five runs (18 g.
) is sublimed to give 10 g.
) of pure quinquephenyl
, m.p. 385–390°
. This can be recrystallized from dimethylsulfoxide
to give well-defined leaflets.
was used without further purification.
A sample of this compound was obtained from Hooker Electrochemical Co. and used without further purification.
The salt begins to precipitate after about 30 minutes.
Commercial anhydrous ethanol
was used throughout.
Prepared by dissolving 1.74 g. of lithium wire in 1 1. of ethanol
After the volume is reduced, a small crystal of iodine
is added whereupon large yellow leaflets of product begin to separate.
The product can be recrystallized readily from dimethylformamide
to give yellow leaflets, m.p. 290–293°
. However, it is pure enough to be used in the next step. This synthesis has also been applied to the preparation of 1,4-bis-[4-(p-tolyl)butadienyl]benzene
), and 1,4-bis-(3-methyl-4-phenylbutadienyl)benzene
is used both for rapid removal of the solvent and to maintain an inert atmosphere.
The acid is added slowly with stirring until a trace of permanent precipitate is formed.
All the steps to this point can be completed in 1 day.
This procedure has been applied to the synthesis of 4,4'''' dimethylquinquephenyl
has been obtained by condensation of cinnamaldehyde
and p-phenylenediacetic acid
with lead oxide
has been prepared by the reaction of biphenyllithium
, followed by dehydration and air oxidation of the dihydroquinquephenyl
by the Gatterman coupling reaction of benzenediazonium formate
by the Ullmann coupling of 4-iodoterphenyl
by the catalytic reduction of p-di-bromobenzene
and the Friedel-Crafts reaction of cyclohexene
followed by dehydrogenation.7
The procedure described represents the best route to both the 1,4-bis-(4-arylbutadienyl)benzenes and quinquephenyls that has been reported.8
The details of the oxidative decarboxylation step for reactions of the type described here have been established by Fieser and Haddadin.9
Chemical Abstracts Nomenclature (Collective Index Number);
hydrochloric acid (7647-01-0)
sodium carbonate (497-19-8)
potassium hydroxide (1310-58-3)
potassium ferricyanide (13746-66-2)
Lithium wire (7439-93-2)
dimethyl formamide (68-12-2)
diethyl acetylenedicarboxylate (762-21-0)
p-phenylenediacetic acid (7325-46-4)
p-Xylylene-bis(triphenylphosphonium chloride) (1519-47-7)
p-xylylene dichloride (623-25-6)
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