Organic Syntheses, CV 6, 179
Submitted by Gary M. Lampman and James C. Aumiller
1.
Checked by G. Nelson and K. B. Wiberg.
1. Procedure
In a
1-l., three-necked, round-bottomed flask, wrapped with aluminum foil to exclude light, and equipped with a
mechanical stirrer, a
reflux condenser, and an
addition funnel, is suspended
37 g. (0.17 mole) of red mercury(II) oxide (Note
1) in
330 ml. of carbon tetrachloride (Note
2). To the flask is added
30.0 g. (0.227 mole) of 3-chlorocyclobutanecarboxylic acid (Note
3). With stirring, the mixture is heated to reflux before a solution of
40 g. (0.25 mole) of bromine in
180 ml. of carbon tetrachloride is added dropwise, but as fast as possible (4–7 minutes) without loss of
bromine from the condenser (Note
4). After a short induction period,
carbon dioxide is evolved at a rate of 150–200 bubbles per minute (Note
5). The solution is allowed to reflux for 25–30 minutes, until the rate of
carbon dioxide evolution slows to about 5 bubbles per minute (Note
5). The mixture is cooled in an
ice bath, and the precipitate is removed by filtration. The residue is washed with
carbon tetrachloride, and the filtrates are combined. The solvent is removed by distillation using a
modified Claisen distillation apparatus with a 6-cm. Vigreux column; vacuum distillation of the residual oil gives
13–17 g. (
35–46%) of
1-bromo-3-chlorocyclobutane, b.p.
67–72° (45 mm.),
n23D 1.5065 (Note
7) and (Note
8).
2. Notes
1. Purified product is available from J. T. Baker Chemical Company.
4. The heating bath should be maintained at about 120° to ensure that the solution continues to reflux while the
bromine solution is added.
5. The gas evolution can be monitored by conducting the gas through rubber tubing from the condenser into a small amount of water where the bubbling can be observed. A small amount of
bromine is lost because of entrainment by the gas.
6. There is no increase in yield on heating the mixture under reflux for 3 hours.
7. The submitters reported a
48–52% yield (
18–20 g.) using the indicated scale, and a
35% yield when the reaction was carried out using twice the scale. The checkers obtained the product in
28–29% yield when the reaction was conducted on a scale 10 times that indicated.
8. The product was analyzed by GC at 130° on a Beckman GC-2 chromatograph equipped with a
180 cm. × 6 mm. column (Beckman 17449) containing 42/60 Johns-Manville C-22 firebrick coated with Dow-Corning 550 silicone oil. The retention times are 12 and 14 minutes for the
trans and
cis compounds, respectively.
3. Discussion
This procedure, a modified Hunsdiecker reaction based upon the method of Cristol and Firth,
2 results in moderate to high yields of bromides and iodides from aliphatic
2,3 and alicyclic carboxylic acids.
4,5,6 Carbon tetrachloride is most frequently used as the solvent, but others can be employed.
3,6 Attempts to prepare chlorides by the method have proved to be unsuccessful.
7
The main advantage of this procedure over that of the standard method
8 is one of convenience. For example, the present method is a one-step reaction while the usual method is a two-step sequence involving an intermediate silver salt. In addition, the presence of water produced in the reaction apparently does not reduce the yield in the present method while water markedly reduces the yield in that involving the silver intermediate.
This preparation is referenced from:
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