Organic Syntheses, Coll. Vol. 4, p.278 (1963); Vol. 38, p.19 (1958).
A solution of sodium methoxide
is prepared from 50 g. (2.17 g. atoms) of freshly cut sodium
and 600 ml. of absolute methanol (Note 1)
in a 3-l. three-necked flask
placed on a steam bath
and equipped with a sealed stirrer (Note 2)
, dropping funnel
, and a condenser
set downward for distillation (Note 3)
. To the stirred solution is added in one portion 344 g. (4.0 moles) of γ-butyrolactone (Note 4)
, and the flask is heated until methanol
distils at a rapid rate. After 475 ml. of methanol
is collected, a filter flask or other suitable device equipped with a side arm is connected to the condenser. This receiver is surrounded by an ice bath
, and reduced pressure from an aspirator is applied cautiously (frothing) with continuous stirring. An additional 50–70 ml. of methanol
is collected in this way. The residue presumably is dibutyrolactone (Note 5)
The condenser is set for reflux, and the steam bath is replaced with a more potent source of heat (electric heating mantle, oil bath
, or direct flame). Concentrated hydrochloric acid
is added with stirring, cautiously at first because a considerable amount of carbon dioxide
is evolved. A total of 800 ml. of acid is added in about 10 minutes (Note 6)
. The mixture is heated under reflux with stirring for 20 minutes, then cooled in an ice bath (Note 7)
. A solution of 480 g. of sodium hydroxide
in 600 ml. of water is added to the stirred mixture as rapidly as possible, without allowing the temperature to go above 50° (Note 8)
. The mixture is then heated under reflux for an additional 30 minutes.
The condenser is arranged for downward distillation, and a total of 650 ml. of ketone-water mixture is collected as distillate. Sufficient potassium carbonate
is added to saturate the aqueous layer, and about 130 ml. of ketone is separated. The aqueous layer is extracted with three 100-ml. portions of ether
, and the combined ether
and ketone layers are dried over 25 g. of anhydrous magnesium sulfate
. The product remaining after removal of the ether
is distilled through an efficient column
. The yield of dicyclopropyl ketone
boiling at 72–74°/33 mm.
1.4654, is 114–121 g.
) (Note 9)
The stirrer should be sturdy and capable of giving vigorous agitation.
It is desirable to have the condenser arranged for reflux during preparation of the methanolic sodium methoxide
, if it is made from sodium metal
Commercial lactone (available from General Aniline and Film Corporation, 435 Hudson Street, New York 14, New York) should be redistilled, b.p. 88–90°/12 mm.
, before use.
can be isolated as a crystalline solid, m.p. 86–87°
, from this residue.2
The preparation can be interrupted at this point without jeopardizing the yield.
The color of the mixture changes from yellow through dark orange to dark reddish brown.
At this point, the following procedure may be used to prepare 1,7-dichloro-4-heptanone
. To the cooled, stirred solution is added 200 ml. of ether
, which brings the dense dichloroketone to the upper layer. The latter is separated, and the acid layer is extracted with two 100-ml. portions of ether
. The combined ether
layers are dried over 25 g. of anhydrous calcium chloride
. After removal of the solvent, the residue is distilled through an efficient column. The yield of 1,7-dichloro-4-heptanone
, b.p. 106–110°/4 mm.
1.4713, is 263–278 g.
). The material takes on a purple cast rapidly and should be stored in a refrigerator.
Considerable salt separates at this point but does not interfere with the subsequent steps.
This procedure is a modification of one recently described in the literature.3
The first step is based on early work of Fittig4
as modified by Spencer and Wright.2
The third step, ring closure of a γ-haloketone,5
is well known (p.597)
. Dicyclopropyl ketone
was reported to form in small amounts from the decarboxylation of cyclopropanecarboxylic acid
but there is some doubt3
about the product.
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