Organic Syntheses, CV 6, 401
Submitted by Ismael Colon, Gary W. Griffin, and E. J. O'Connell Jr
1.
Checked by Stephen P. Peters and Kenneth B. Wiberg.
1. Procedure
A
1-l., three-necked, round-bottomed flask equipped with a
magnetic stirrer and a
dropping funnel is charged with
35 g. (0.14 mole) of 1,3-dibenzoylpropane (Note
1) and a solution of
11.2 g. (0.280 mole) of sodium hydroxide in
400 ml. of methanol. The mixture is warmed to 45°, with stirring to dissolve the diketone. It is allowed to cool to 40°, and a solution of
35 g. (0.14 mole) of iodine in 200 ml. of methanol is slowly added to the stirred solution from the dropping funnel (Note
2). After the addition of
iodine is completed, the resulting clear solution is stirred at room temperature for 1.5 hours. During this period, a white solid precipitates (Note
3). The mixture is filtered and the filtrate is placed in a round-bottomed flask. The white solid is washed with four, 100-ml. portions of water and dried at 1 mm. at 57° (1 mm.) for 15 hours, yielding
23–25 g. (
66–72%) of
trans-1,2-dibenzoylcyclopropane, m.p.
103–104° (Note
4). Additional material is obtained on evaporation of the filtrate using a
rotary evaporator. The pale-red solid residue is treated with
25 ml. of aqueous 10% sodium bisulfite (Note
5), filtered, and dried as above giving
8–9 g. (
23–26%) of the product, m.p.
95–98°. Recrystallization from
methanol affords greater than
90% recovery of
trans-1,2-dibenzoylcyclopropane, m.p.
102–103°. For the recrystallization of a
10-g. sample
200 ml. of methanol is used.
2. Notes
2. The
iodine solution is added at a rate such that the color of the
iodine is continually discharged by the rapidly stirred solution.
3. In some cases the precipitate may begin to form during the addition of the
iodine solution. This has no effect on the yield.
4. Pertinent spectral data include a carbonyl stretching band in the IR at 1665 cm.
−1 and UV absorption maxima at 245 nm (ε 31,300), 278 nm (ε 2130), and 317 nm (ε 194). The
1H NMR spectrum (CCl
4) has two triplets of equal intensity at δ 3.32 and 1.68 in addition to the aromatic proton bands at δ 7.3–8.2. The integrated peak areas are in the ratio 1:1:5.
3. Discussion

Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
methanol (67-56-1)
sodium hydroxide (1310-73-2)
sodium bisulfite (7631-90-5)
iodine (7553-56-2)
zinc (7440-66-6)
sodium iodide (7681-82-5)
1,4-Dibenzoylbutane (3375-38-0)
1,3-dibenzoylpropane (6263-83-8)
1,3-Dibenzoylcyclopropane
trans-1,2-Dibenzoylcyclopropane,
Methanone, 1,2-cyclopropanediylbis[phenyl]-, trans- (38400-84-9)
trans-1,2-bis(4-methoxybenzoyl)cyclopropane
trans-1,2-bis(2-methoxy-5-methylbenzoyl)cyclopropane
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