MATVEEVA et al.
1472
10 min at 0–5°C until it became homogeneous; the
disappearance of triphenylphosphine was monitored by
TLC. A solution of 3 mmol of carboxylic acid in 2 ml
of methylene chloride was then added, and the mixture
was stirred for 1 h at 5–10°C. The product was isolated
by vacuum distillation. Below are given R in RCOBr,
yield, and boiling point (p, mm): s-Bu, 70%, 60°C
(13); t-Bu, 30%, 65°C (15); Ph, 60%, 143°C (13) [12].
α-Bromophenylacetic acid (XXI). A solution of
1.64 g (4 mmol) of 2,4,4,6-tetrabromo-2,5-cyclohexa-
dienone (I) in 5 ml of methylene chloride was added to
a solution of 1.05 g (4 mmol) of triphenylphosphine in
10 ml of methylene chloride. The mixture was stirred
for 10 min, and 0.15 g (1 mmol) of (–)-(R)-mandelic
acid, [α]D = –151° (c = 0.43, ethanol), was added. The
mixture was stirred for 1.5 h at room temperature and
treated with an aqueous solution of sodium hydrogen
carbonate to hydrolyze acid bromide, and the aqueous
phase was separated, acidified with hydrochloric acid
to a weakly acidic reaction, and extracted with diethyl
ether (5×5 ml). The extract was evaporated to obtain
0.1 g of α-bromophenylacetic acid, [α]D = +45°
(c = 0.43, ethanol) [10].
Carboxylic acid anilides. A solution of 3 mmol of
2,4,4,6-tetrabromo-2,5-cyclohexadienone (I) in 5 ml of
methylene chloride was added to a solution of 3 mmol
of triphenylphosphine in 10 ml of methylene chloride,
cooled to 0°C. The mixture was stirred for 10 min at
0–5°C until it became homogeneous; the disappear-
ance of triphenylphosphine was monitored by TLC.
A solution of 3 mmol of carboxylic acid in 2 ml of
methylene chloride was then added, the mixture was
stirred for 1 h at 5–10°C, and 6 mmol of aniline was
added under stirring. A white solid immediately sepa-
rated from the solution. The precipitate was filtered off
and washed with methylene chloride, the filtrate was
evaporated on a rotary evaporator, and the residue was
subjected to column chromatography on silica gel. The
column was eluted with hexane to isolate 2,4,6-tri-
bromophenol (III), and the subsequent elution with
chloroform gave the corresponding anilide (the yields
are given in table).
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 01-03-33085), by the program “Universities of
Russia” (project no. 05.03.003), and by the grant of
the President of the Russian Federation for support
of higher school (project no. VSh-2051.2003.3).
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 10 2004