Org. Synth. 1947, 27, 30
Submitted by C. F. H. Allen, J. W. Gates, Jr., and J. A. VanAllan.
Checked by R. L. Shriner and H. W. Johnston.
A solution of phenylmagnesium bromide
is prepared in the usual manner1
using 12.2 g. (0.5 gram atom) of magnesium
, 78.5 g. (52 ml., 0.5 mole) of bromobenzene
, and 500 ml. of absolute ether
in a 2-l. round-bottomed three-necked flask
fitted with a reflux condenser
, a mechanical stirrer
, and a dropping funnel
. No unreacted magnesium
should remain; if any does, an additional 1–2 ml. of bromobenzene
should be added.
To this vigorously stirred solution is added slowly a solution of 44.5 g. (0.20 mole) of benzalphthalide2
in 400 ml. of dry benzene
. After about half of this solution has been added, the magnesium complex
begins to separate; it hinders the stirring somewhat. When all the phthalide solution has been admitted (about 1 hour), the reflux condenser is replaced by a still head carrying a thermometer
and attached to a condenser set
for downward distillation. The bulk of the solvent is then removed; this requires about 30 minutes, the temperature of the vapor remaining at 50° for about half this time and rising to about 65° toward the end. About 220–230 ml. of distillate is obtained. The flask and contents are then immersed in an ice bath
, and the magnesium complex
is decomposed by the slow addition of a cold solution of 15 ml. of concentrated sulfuric acid
in 300 ml. of water (Note 1)
with rapid stirring. The upper benzene
layer is separated and transferred to a 1-l. Claisen flask
, and the solvent is removed by distillation from a steam bath
; this requires about 4 hours. The residual thick red syrup is transferred to a 125-ml. Claisen flask
with a wide side arm set up for vacuum distillation. The residue is heated under a pressure of about 10 mm. to remove all low-boiling material (Note 2)
and then is distilled under reduced pressure. The fraction boiling at 215–255°/6 mm. (195–220°/1 mm.) is collected, most of the distillate coming over at 235–240°/6 mm. The distillate is dissolved in 50 ml. of boiling benzene
, 200 ml. of hot 95% ethanol
is added, and the solution is chilled in an ice bath for 2 hours. The red, crystalline 2,3-diphenylindone
is collected on a filter, washed with 50 ml. of cold 95% ethanol
, and air-dried. The yield is 34–40 g.
) of red crystals melting at 149–151° (Note 3)
and (Note 4)
The decomposition is vigorous, and the acid must be admitted slowly at first but may be added more rapidly toward the end.
During this heating any carbinol present is dehydrated. Low and erratic yields usually indicate incomplete dehydration.
The product may be recrystallized by dissolving it in 50 ml. of boiling benzene
and diluting with 200 ml. of hot ethanol
. The recovery of material, m.p. 150–151°
, is about 90%
This procedure is capable of considerable variation, by which other indenones may be secured. For example, the benzalphthalide
may be replaced by other phthalides made from (a
) other aldehydes, or (b
) other anhydrides; the phenylmagnesium bromide
can be replaced by other Grignard reagents.
has been prepared by the action of phenylmagnesium bromide
and by ring closure from α,β-diphenylcinnamic acid5,6
or from 2,3,3-triphenyl-3-hydroxypropionic acid
Chemical Abstracts Nomenclature (Collective Index Number);
sulfuric acid (7664-93-9)
Phenylmagnesium bromide (100-58-3)
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