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Organic Synthess - McKusick B.C.

McKusick B.C., Boekelheide V., Emmons W.D. Organic Synthess - New York, 1963. - 134 p.
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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-mi. Erlenmeyer flask. The solution is kept at 0-5° in a refrigerator for 1 hour, during which time a-benzylidene-'y-phenyl-A^r-butenoIide 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-j8-sulfonate.8 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.4
3. 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. Methods of Preparation
a-Benzylidene-7-phenyl-M7-butenolide has been prepared by the condensation of benzaldehyde with 3-benzoylpropionic acid in the presence of acetic anhydride and sodium acetate.6'e
4. Merits of the Preparation
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. y-Lactones such as a-benzylidene-7-phenyl-A^T-bu-tenolide 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.7 a-Benzylidene-7-phenyl-A3''1'-butenolide is smoothly isomerized by aluminum chloride to 4-phenyl-2-naphthoic acid * in 65-75% yield via intramolecular alkylation.
1 Department of Chemistry, Illinois Institute of Technology, Chicago 16, Illinois.
* L. F. Somerville and C. F. H. Allen, Org. Syntheses, Coll. Vol. 2, 81 (1943).
* L. J. Brady, Anal. Ckem., 20, 1033 (1948).
4 E. Klingsberg, Chem. Rev., 54, 59 (1954).
‘ W. Borsche, Chem. Ber., 47, 1108, 2718 (1914).
* F. W. Schueler and C. Hanna, J. Am. Chem. Soc., 73, 3528 (1951).
7 R. Filler and L. M. Hebron, J. Am. Chem. Soc., 81, 391 (1959).
8 R. Filler, L. H. Mark, and E. J. Kasek, J. Org. Chem., 24,1780 (1959).
2-BROMOALLYLAMINE (AUylamine, 2-bromo-)
CH2=C—CH2Br + C6HI2N4 -^>
ch2=c—ch2nc6h12n3 Br 4HC1'6->
I + — NaOH
6CH20 + 3NH4C1 + CH2=C-~CH2NH3 Cl -5-
CH2=C—CH2NH2 + H20 + NaCI
Submitted by Albert T. Bottini, Vasu Dev, and Jane Khhck,1 Checked by A. S. Pagano and W. D. Emmons.
1. Procedure
Cautionl Contact with 2-bromoallylamine can cause severe eye and skin irritation. This preparation should be carried out in a good hood, and the operator should wear protective goggles and rubber gloves.
A. 2-Bromoallylhexamimum bromide. A 2-1. three-necked flask fitted with a Hershberg stirrer,2 a dropping funnel, and a condenser is charged with a solution of 154 g. (1.10 moles) of hexamethylenetetramine (Note 1) in 1250 ml. of chloroform. The solution is stirred and heated under reflux while 200 g. (1.00 mole) of 2,3-dibromopropene (Note 2) is added dropwise over a period of 1 hour. Precipitation of the product is noted soon after the first addition of 2,3-dibromopropene. After the addition is complete, the reaction mixture is stirred under reflux for 3 hours and allowed to stand overnight. The mixture is cooled in an ice bath, and the salt is collected by suction filtration. After air-
drying, the crude yellow 2-bromoallylhexaminium bromide weighs 292-308 g. (86-91%) and melts at 183-186°.
B. 2-Bromoallylamme. Crude 2-bromoallylhexammiuin bromide (204 g., 0.60 mole) is dissolved in a warm solution prepared from 400 ml. of water, 2 1. of ethanol, and 480 ml. (5.8 moles) of UN hydrochloric acid. A white precipitate of ammonium chloride forms within an hour. The reaction mixture is allowed to stand for 24 hours, and the precipitate is removed by suction filtration. The mother liquor is concentrated to a volume of 600 ml. (Note 3), and the precipitate (Note 4) is removed by suction filtration. The mother liquor is evaporated to dryness (Note 5), and the residue is dissolved in 300 ml. of water. The solution is cooled in an ice bath and made strongly alkaline (pH 13) with 6N sodium hydroxide solution.
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