Org. Synth. 1965, 45, 14
DOI: 10.15227/orgsyn.045.0014
D,L-10-CAMPHORSULFONYL CHLORIDE
Submitted by Paul D. Bartlett and L. H. Knox
1.
Checked by John D. Roberts
1. Procedure
In a
2-l., three-necked, round-bottomed flask (Note 1) fitted with a
sealed stirrer having a Teflon® blade and, on the two side necks, with
gas-outlet tubes connected by rubber or plastic tubing to an efficient hydrogen chloride absorption trap (Note 2),
464 g. (2 moles) of D,L-10-camphorsulfonic acid (Note 3) is mixed with
416 g. (2 moles) of phosphorus pentachloride (Note 4). The flask is immersed in ice water and, as soon as the mixture has liquefied sufficiently, the stirrer is started but must be run slowly at first because of lumps. When the vigorous reaction has subsided, the
cooling bath is removed and stirring continued until the chloride is completely dissolved
(Note 5). The mixture is then allowed to stand for 3 or 4 hours. It is poured (
Hood!) onto 500 g. of crushed ice contained in a
2-l. beaker. This mixture is immediately poured into a second beaker containing a similar quantity of crushed ice. The mixture is then poured back and forth between the two beakers until all evidence of reaction has disappeared
(Note 6). The fine white product is collected on a
suction filter and washed several times with cold water. The yield is essentially quantitative (500 g.) of moist sulfonyl chloride which is pure enough to be used for the preparation of
D,L-ketopinic acid (
p. 55). When carefully dried, the crude material has m.p.
81–83° (Note 7) and
(Note 8) and may be preserved in a
desiccator.
2. Notes
1.
The checker found it expedient to carry on the reaction in a
2-l. Pyrex® reaction kettle (Corning 6947), the large closure making the initial mixing of the solid reactant and the removal of the product much simpler.
3.
The
D,L-10-camphorsulfonic acid employed is the unrecrystallized product described on
p. 194.
4.
The initial mixing is conveniently made by turning the stirrer back and forth by hand.
5.
The mixture does not usually become a clear solution because the product begins to crystallize. It is not difficult, however, to recognize yellow lumps of unreacted
phosphorus pentachloride.
6.
10-Camphorsulfonyl chloride is rather rapidly hydrolyzed by warm water. The procedure here provides for complete hydrolysis of
phosphorus oxychloride and excess
phosphorus pentachloride without local heating and loss of product due to hydrolysis. For best results, the whole hydrolysis operation should be carried out quickly and steadily. It is well to have additional quantities of crushed ice on hand because the mixture may become quite hot if all of the ice added initially melts.
7.
If the crude moist sulfonyl chloride is to be preserved, it must be thoroughly and reasonably rapidly dried. The checker found it very convenient to use a "freeze-drying" apparatus to remove the bulk of the moisture.
8.
The submitters report that crystallization of the crude product from
ligroin produces material of m.p.
83–84°. The sulfonyl chloride from
(+)-camphorsulfonic acid has m.p.
67–68°.
3. Discussion
The procedure described here is adapted from that of Reychler.
2 The chloride may also be made from treatment of the acid with
thionyl chloride.
34. Merits of the Preparation
D,L-10-Camphorsulfonyl chloride may be oxidized to
ketopinic acid (
p. 690). The optically active forms of the sulfonyl chloride are useful for resolving alcohols and amines into optical antipodes.
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ligroin
D,L-ketopinic acid
ketopinic acid
phosphorus pentachloride (10026-13-8)
thionyl chloride (7719-09-7)
Phosphorus Oxychloride (21295-50-1)
D,L-10-CAMPHORSULFONIC ACID (5872-08-2)
10-CAMPHORSULFONYL CHLORIDE,
D,L-10-CAMPHORSULFONYL CHLORIDE (6994-93-0)
(+)-camphorsulfonic acid (3144-16-9)
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