Org. Synth. 1963, 43, 3
DOI: 10.15227/orgsyn.043.0003
α-BENZYLIDENE-γ-PHENYL-Δβ,γ-BUTENOLIDE
[Cinnamic acid, α-(β-hydroxystyryl)-, γ-lactone]
Submitted by Robert Filler, Edmund J. Piasek, and Hans A. Leipold
1.
Checked by S. Trofimenko and B. C. McKusick.
1. Procedure
The apparatus consists of a 200-ml., three-necked, round-bottomed flask fitted with thermometer, reflux condenser, and gas-inlet tube. The flask is charged with 17.8 g. (0.10 mole) of 3-benzoylpropionic acid (Note 1), 10.6 g. (10.6 ml., 0.10 mole) of benzaldehyde, 61.3 g. (57 ml., 0.60 mole) of acetic anhydride, and 8.2 g. (0.10 mole) of powdered anhydrous sodium acetate (freshly fused). The flask is placed in an oil bath maintained at a temperature of 95–100° and is kept there for 2 hours while dry oxygen-free nitrogen is passed through the reaction mixture (Note 2). At the end of this time the flask is removed from the oil bath, and the hot solution is decanted from the sodium acetate into a 250-ml. Erlenmeyer flask. The solution is kept at 0–5° in a refrigerator for 1 hour, during which time α-benzylidene-γ-phenyl-Δβ,γ-butenolide separates as an orange solid.
About 40 ml. of 95% ethanol is added to the contents of the flask, and the butenolide is brought into suspension by thoroughly breaking up all lumps with a spatula. The suspension is filtered with suction, and the filter cake is washed with 30 ml. of cold 95% ethanol and then with 100 ml. of boiling water to remove any sodium acetate present. The butenolide is obtained as a yellow solid, m.p. 149–154°, weight 11.1–12.4 g. (45–50%), after being dried overnight in a vacuum desiccator. This product, which is pure enough for most purposes, may be further purified by crystallization from 95% ethanol (Note 3).
2. Notes
1.
3-Benzoylpropionic acid2 is available from Aldrich Chemical Co., Milwaukee, Wisconsin.2.
Oxygen is removed from the
nitrogen gas by passing the latter through Brady solution, which consists of
zinc amalgam,
sodium hydroxide, and
sodium anthraquinone-β-sulfonate.
3 It has been shown that oxidizing agents induce formation of a Pechmann dye, a deep red substance which is difficult to remove from the butenolide.
43.
About
75 ml. of ethanol is used for every gram of butenolide to be dissolved. Clarification of the solution with charcoal should be avoided because the butenolide tends to separate from solution during filtration and clogs the
steam-jacketed funnel. The crystallized butenolide melts at
150–152°.
3. Discussion
α-Benzylidene-γ-phenyl-Δβ,γ-butenolide has been prepared by the condensation of
benzaldehyde with
3-benzoylpropionic acid in the presence of
acetic anhydride and
sodium acetate5,6 or in the presence of a mixture of
dimethylformamide and
sulfur trioxide.
7 The butenolide has also been obtained by reaction of
α-chloromethylene-γ-phenyl-Δβ,γ-butenolide with
benzene in the presence of anhydrous
aluminum chloride.
8
The method described above may be used for the preparation of a wide variety of butenolides substituted in the arylidene ring with either electron-withdrawing or electron-releasing substituents. γ-Lactones such as α-
benzylidene-γ-phenyl-Δβ,γ-butenolide are isoelectronic with azlactones, but have received much less attention. Like the azlactone ring, the butenolide ring may be opened readily by water, alcohols, or amines to form keto acids, keto esters, or keto amides.
9 α-Benzylidene-γ-phenyl-Δβ,γ-butenolide is smoothly isomerized by
aluminum chloride to
4-phenyl-2-naphthoic acid10 in 70% yield via intramolecular alkylation. Grignard reagents add
1,4 to the α,β-unsaturated carbonyl system, with the lactone ring remaining intact,
11 while
phenyllithium leads to ring opening and the formation of
1,1-diphenyl-2-phenacylcinnamyl alcohol.
11 The butenolide gives reduced dilactones, on treatment with
lithium aluminum hydride.
12
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
α-Benzylidene-γ-phenyl-Δβ,γ-butenolide
α-chloromethylene-γ-phenyl-Δβ,γ-butenolide
benzylidene-γ-phenyl-Δβ,γ-butenolide
1,4 to the α,β-unsaturated carbonyl
ethanol (64-17-5)
Benzene (71-43-2)
acetic anhydride (108-24-7)
sodium acetate (127-09-3)
sodium hydroxide (1310-73-2)
sulfur trioxide (7446-11-9)
oxygen (7782-44-7)
nitrogen (7727-37-9)
benzaldehyde (100-52-7)
aluminum chloride (3495-54-3)
zinc (7440-66-6)
Phenyllithium (591-51-5)
3-benzoylpropionic acid (2051-95-8)
lithium aluminum hydride (16853-85-3)
dimethylformamide (68-12-2)
sodium anthraquinone-β-sulfonate (131-08-8)
4-phenyl-2-naphthoic acid
1,1-diphenyl-2-phenacylcinnamyl alcohol
Cinnamic acid, α-(β-hydroxystyryl)-, γ-lactone (4361-96-0)
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