Field of the invention
The present invention relates to the process for preparing 2,2-dichlorobenzo-1,3-dioxole of
Formula I. The present invention also relates to the process for preparing 5-bromo-2,2-
difluorobenzo-1,3-dioxole of Formula III.
Background of the invention
The dichlorobenzodioxole and substituted difluorobenzodioxole play an important role as
precursors for the preparation of medicaments and crop protection agents.
O
O
Cl
Cl
Formula I
O
O
F
F
Br
Formula III
The EP Patent No. 1,502,908 provides a process for the preparation of 2, 2-dichloro-1, 3-
benzodioxole by reacting 1, 3-benzodioxole with chlorine in the presence of a radical
initiator, in dichlorobenzotrifluoride as solvent. The dichlorobenzotrifluoride used in the
process has boiling point of 130oC, which is very close to the boiling point of 2,4-dichloro3
benzotrifluoride (i.e. 117oC). Thus, there arises a difficulty in the separation of dichloro
product.
The U.S Patent No. 7,148,365 describes a process for the preparation of 5-bromo-2, 2-
difluorobenzo-1, 3-dioxoles by reaction of 2, 2-difluorobenzo-1, 3-dioxoles with bromine
in the presence of at least two Friedel-Crafts catalysts of which one is hydrogen fluoride.
The U.S. Pat. No. 4,895,871 describes a bromination of 2, 2-difluorobenzo-1, 3-dioxole
with elemental bromine in carbon tetrachloride. Owing to the toxicity of carbon
tetrachloride, this process is unpracticable for industrial use. Additionally, the yield is low.
Thus, there is a need in the art to provide simple, cost-effective and industrially scalable
process for the preparation of compound of Formula I and Formula III.
Summary of the Invention
The present invention provides a process for the preparation of compound of Formula I,
comprising;
a) reacting a compound of Formula II with chlorine in the presence of
pentafluorobenzene and a radical initiator to obtain a compound of Formula I, and
b) isolating the compound of Formula I from step a).
O
O
O
O
Cl
Cl
Formula II Formula I
The present invention also provides a process for the preparation of compound of Formula
III, comprising;
4
a) reacting a compound of Formula IV with bromine to obtain a compound of
Formula III, and
b) isolating the compound of Formula III from step a), wherein step a) is carried out
in the absence of a catalyst.
O
O
F
F
O
O
F
F
Br
Formula IV Formula III
Detailed Description of the Invention
In an aspect, the present invention provides a process for the preparation of compound of
Formula I, comprising;
a) reacting a compound of Formula II with chlorine in the presence of
pentafluorobenzene and a radical initiator to obtain a compound of Formula I,
and
b) isolating the compound of Formula I from step a).
O
O
O
O
Cl
Cl
Formula II Formula I
The compound of Formula II may be commercially obtained or prepared by any method
known in the art.
The radical initiator in step a) is selected from irradiation with ultra-violet light,
azobisisobutyronitrile, 1,1'-azobis(cyclohexanecarbonitrile), di-tert-butyl peroxide,
benzoyl peroxide, methylethylketone peroxide and acetone peroxide.
5
The step a) may be carried at a temperature in the range of from about 25oC to about
100oC.
The compound of Formula I is isolated from step a) reaction mixture. The compound of
Formula I may be isolated by layer separation, distillation, extraction, evaporation or a
combination thereof.
In another aspect, the present invention provides a process for the preparation of
compound of Formula III, comprising;
a) reacting a compound of Formula IV with bromine to obtain a compound of
Formula III, and
b) isolating the compound of Formula III from step a), wherein step a) is
carried out in the absence of a catalyst.
O
O
F
F
O
O
F
F
Br
Formula IV Formula III
The compound of Formula IV may be prepared by any method known in the art, for
example, method known in U.S Patent No. 4,895,871.
The step a) may be carried out in the presence of water.
The step a) may be carried at a temperature in the range of from about 10oC to about 85oC.
The compound of Formula III is isolated from step a) reaction mixture. The compound of
Formula III may be isolated by layer separation, distillation, extraction, evaporation or a
combination thereof.
6
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
Examples
Example 1: Preparation of 2, 2-dichloro-1,3-benzodioxole
Pentafluorobenzene (718g, 4.92mol) was taken in a 2000ml round-bottomed flask fitted with a magnetic stirrer, reflux condenser, pressure equalizing addition funnel, and drying tube. Azobisisobutyronitrile(1.5g,0.009mol), 1,3-benzodioxole(300g, 2.46mol) and chlorine (358g,5.04mol) were added simultaneously to the flask at 85°C. The temperature of the mass was maintained at 85°C for one hour for reaction completion. The progress of the reaction was monitored by gas chromatography. The temperature of the mass was then brought down to 25°C and nitrogen gas was passed for two hours to remove excess chlorine and dissolved hydrogen chloride. The title compound was purified under vacuum.
Yield (%) : 90
Purity (%) : 98 (by gas chromatography)
Example 2: Preparation of 5-bromo-2,2-difluorobenzo-1,3-dioxole
2, 2-difluoro-1, 3-benzodioxole (200g, 1.27mol) and water (456g, 25.3mol) were placed in a 1000 mL round-bottomed flask fitted with a mechanical stirrer, reflux condenser and pressure equalizing addition funnel. Bromine (284g, 1.77mol) was added drop-wise at 25°C for one hour. During addition, the temperature of the mass was raised from 25°C to 85°C. The temperature of the reaction mass was maintained at 85°C for 8 hours. The progress of the reaction was monitored by liquid chromatography. The temperature of the reaction mass was brought down to 25°C. The layers were separated, the organic layer was washed with sodium bisulphite solution followed by sodium bicarbonate solutionto obtain the title compound. The crude mass was purified by vacuum distillation.
Yield (%) : 80
Purity (%) : 99.8 (by liquid chromatography)

We Claim
1. A process for the preparation of compound of Formula I, comprising;
a) reacting a compound of Formula II with chlorine in the presence of
pentafluorobenzene and a radical initiator to obtain a compound of Formula I, and
b) isolating the compound of Formula I from step a).
O
O
O
O
Cl
Cl
Formula II Formula I
2. The process as claimed in claim 1, wherein the radical initiator in step a) is selected
from the group consisting of irradiation with ultra-violet light,
azobisisobutyronitrile, 1,1'-azobis(cyclohexanecarbonitrile), di-tert-butyl peroxide,
benzoyl peroxide, methylethylketone peroxide and acetone peroxide or mixture
thereof.
3. The process as claimed in claim 1, wherein the step a) is carried at a temperature in
the range of 25oC to 100oC.
4. A process for the preparation of compound of Formula III, comprising;
a) reacting a compound of Formula IV with bromine to obtain a compound of
Formula III, and
b) isolating the compound of Formula III from step a), wherein step a) is carried out
in the absence of a catalyst.
O
O
F
F
O
O
F
F
Br
Formula IV Formula III