inserted into the reaction mixture through a condenser and/or
by infrared reading.
by filtration and dried to give 1.61 g (92%) for ethyl acetate and
1.7 g (97%) for diethyl carbonate of succinimide. The filtrate
was then evaporated under vacuum to a powdery material which
was subjected to silica gel column chromatography with hexane–
ethyl acetate (1 : 4) as an eluate. The isolated yield of ~96% pure
product (HPLC) is 1.36 g (70%) for ethyl acetate and 1.75 g (90%)
Monobromination procedure A (the product is soluble
at 5 ◦C in the reaction media). Preparation of 1-bromo-4-
(bromomethyl)benzene (2c)
1
for diethyl carbonate as reaction media. H-NMR d 7.47 (2H,
To an ethyl acetate (15 ml) or diethyl carbonate (10 ml) solution
of 4-bromotoluene (1 g, 5.9 mmol), was added benzoyl peroxide
(5 mg; 0.02 mmol, 0.34 mol %) and N-bromosuccinimide (1.89 g,
10.6 mmol, 1.8 equivalents). The reaction mixture was refluxed
(30 min for ethyl acetate and 20 min for diethyl carbonate) under
microwave heating (magnetron power of 400 W for ethyl acetate
and 450 W diethyl carbonate). The clear reaction mixture was
cooled at 5 ◦C for 4–5 h. Formed white precipitate was separated
by filtration and dried to give 990 mg (94%) for ethyl acetate and
1.0 g (95%) for diethyl carbonate of succinimide. The filtrate was
then evaporated under vacuum, to obtain a powdery material,
which was purified by silica gel column chromatography with
hexane–ethyl acetate (1 : 4) as an eluent. The isolated yield of 1-
bromo-4-bromomethylbenzene is 1.33 g (90%) for ethyl acetate
d, J = 8.4 Hz), 7.26 (2H, d, J = 8.4 Hz), and 6.68 (s, 1H) ppm.
13C-NMR d 137.05, 132.23, 130.96, 122.73, and 40.05 ppm.
Dibromination procedure D (product insoluble in reaction
media at room temperature). Preparation of
2-(4-(dibromomethyl)phenyl)isoindoline-1,3-dione (3g)
The ethyl acetate (15 ml) or diethyl carbonate (10 ml) suspension
of 2-p-tolylisoindoline-1,3-dione (1 g, 4.2 mmol), benzoyl per-
oxide (5 mg; 0.02 mmol, 0.34 mol %), and N-bromosuccinimide
(2.25 g, 12.6 mmol, 3 equivalents) was refluxed for 80 min (ethyl
acetate) or 30 min (diethyl carbonate) and under microwave
heating (magnetron power of 500 W for ethyl acetate and 600
W for diethyl carbonate). The clear reaction mixture was cooled
down to room temperature. Formed white crystalline product
was separated by filtration, washed with ice cold solvent and
dried at room temperature. According to the HPLC the product
is ~97% pure. The isolated yield of 3 g was 1.2 g (70%) for
ethyl acetate and 1.32 g (85%) for diethyl carbonate as reaction
media. 1H NMR d 7.96–7.98 (m, 2H), 7.81–7.83 (m, 2H), 7.5–
7.7 (d, J = 8.42 Hz, 2H), 7.49–7.52 (d, J = 8.42 Hz, 2H), 6.68
(s, 1H) ppm. 13C-NMR d 40.04, 124.18, 126.55, 127.65, 131.82,
133.06, 134.88, 141.45, and 167.20 ppm. Filtrate was left at 5 ◦C
overnight. Formed white precipitate was separated by filtration
and dried to give 1.5 g (86%) for ethyl acetate and 1.6 g (92%)
for diethyl carbonate of succinimide.
1
and 1.40 g (95%) for diethyl carbonate as reaction media. H-
NMR d 7.47 (2H, d, J = 8.4 Hz), 7.26 (2H, d, J = 8.4 Hz), 4.44
(2H, s) ppm. 13C-NMR d 137.05, 132.23, 122.73, and 32.69 ppm.
Monobromination procedure B (the product is insoluble in
reaction media at room temperature). Preparation of
2-(4-(bromomethyl)phenyl)isoindoline-1,3-dione (2g)
Benzoyl peroxide (5 mg; 0.02 mmol, 0.34 mol %) was added into
a reaction mixture that consists of solvent (15 ml for ethyl acetate
or 10 ml for diethyl carbonate), 2-p-tolylisoindoline-1,3-dione
(1 g, 4.2 mmol) and N-bromosuccinimide (1.35g,7.6 mmol, 1.8
equivalents). The resulting reaction mixture was refluxed for 30
min under microwave heating (magnetron power 400 W for ethyl
acetate and 450 W for diethyl carbonate). The clear reaction
mixture was cooled down to room temperature. Formed white
crystalline product was separated by filtration, washed with ice
cold solvent and dried at room temperature. According to the
HPLC, the product is around ~98% pure. The yield is 1.2 g
(90%) for ethyl acetate as a solvent and 1.26 g (95%) for diethyl
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1
carbonate as a reaction media. H-NMR d 7.94–7.97 (m, 2H),
7.78–7.81 (m, 2H), 7.51–7.55 (d, J = 8.42 Hz, 2H), 7.43–7.47 (d,
J = 8.42 Hz, 2H), 4.52 (s, 2H) ppm. 13C-NMR d 32.82, 124.09,
126.92, 130.07, 131.89, 134.78, 137.72, and 167.35 ppm. The
filtrate was left at 5 ◦C overnight. Formed white precipitate was
separated by filtration and dried to give 925 mg (88%) for ethyl
acetate and 967 mg (93%) for diethyl carbonate of succinimide.
Dibromination procedure C (product soluble in reaction media).
Preparation of 1-bromo-4-(dibromomethyl)benzene (3c)
The ethyl acetate (15 ml) or diethyl carbonate (10 ml) suspension
of 4-bromotoluene (1 g, 5.9 mmol), benzoyl peroxide (5 mg;
0.02 mmol; 0.34 mol %) and N-bromosuccinimide (3.16 g, 17.7
mmol, 3 equivalents) was refluxed (30 min for ethyl acetate
and 20 min for diethyl carbonate) under microwave heating
(microwave magnetron power of 500 W for ethyl acetate and
600 W for diethyl carbonate). Clear reaction mixture was cooled
18 A. Podgorsek, S. Stavber, M. Zupan and J. Iskra, Tetrahedron, 2009,
65, 4429–4439.
19 M. Jareb, M. Zupan and S. Staber, Helv. Chim. Acta, 2009, 92, 555–
565.
◦
at 5 C for 4–5 h. The formed white precipitate was separated
932 | Green Chem., 2011, 13, 928–933
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