Org. Synth. 1960, 40, 36
Submitted by Richard N. McDonald and Tod W. Campbell1
Checked by M. S. Newman, R. Marshall, and W. N. White.
A. Triphenylcinnamylphosphonium chloride. A mixture of 40 g. (0.26 mole) of (3-chloropropenyl) benzene (Note 1) and 92 g. (0.35 mole) of triphenylphosphine (Note 2) in 500 ml. of xylene is heated at reflux for 12 hours with stirring. The mixture is allowed to cool to about 60°, and the colorless crystalline product is filtered, washed with 100 ml. of xylene, and dried in a vacuum oven at about 20 mm. pressure and 60° to constant weight. The yield is 99–101 g. (91–93%), m.p. 224–226° (Note 3).
B. 1,4-Diphenylbutadiene. To a solution of 60.0 g. (0.145 mole) of triphenylcinnamylphosphonium chloride and 16.4 g. (0.155 mole) of benzaldehyde in 200 ml. of ethanol (Note 4) is added 760 ml. of 0.2M lithium ethoxide in ethanol (Note 5) and (Note 6). After allowing this mixture to stand 30 minutes, 700 ml. of water is added (Note 7) and the colorless crystals are filtered, washed with 150 ml. of 60% ethanol, and dried in the vacuum oven at 65°. The yield of crystalline product, m.p. 153–156°, is 17.9–19.9 g. (60–67%) (Note 8). The product is the trans-trans isomer and is pure enough for most purposes (Note 9). Recrystallization from cyclohexane gives a product with m.p. 154–156°.
Eastman Organic Chemicals, white label grade, used without purification.
was used without further purification. Metal and Thermit Corp., Rahway, New Jersey, now offers this reagent for sale at a modest price.
The phosphonium salt can be recrystallized to analytical purity by dissolving in a small amount of boiling ethanol
, adding ether
at the boil until cloudy, and allowing the salt to crystallize in a refrigerator
Commercial anhydrous ethanol
was used throughout without further purification.
The lithium ethoxide
solution is prepared by dissolving 1.40 g. of lithium wire in 1 l. of anhydrous ethanol
A transient orange color is immediately formed, and it is replaced by crystallization of the product in about 1 minute.
is soluble in 60% aqueous ethanol
; therefore it remains in the filtrate and affords no difficulty.
The yield can probably be increased by carrying out the reaction in an ether solvent with an alkyllithium as base, but the simplicity and relative ease of the conditions described appear to make the possible yield advantage secondary.
This procedure has been applied successfully to the synthesis of substituted bistyryls, i.e., 1-(p-tolyl)-4-phenylbutadiene
), and 1-(4-acetamidophenyl)-4-phenylbutadiene
), by using the corresponding substituted benzaldehydes.
has been obtained from phenylacetic acid
with lead oxide
by the dehydrogenation of 1,4-diphenyl-2-butene
and by the coupling reaction of benzenediazonium chloride
and cinnamylideneacetic acid
The present method5
gives better yields than those previously reported, is adaptable to the preparation of a variety of substituted bistyryls, and is relatively easy to carry out.
Chemical Abstracts Nomenclature (Collective Index Number);
Phenylacetic acid (103-82-2)
Lithium wire (7439-93-2)
triphenylphosphine oxide (791-28-6)
(3-chloropropenyl) benzene (21087-29-6)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved