PROCESS FOR THE PREPARATION OF 4-TRIFLUOROMETHOXYPHENOL
Field of the Invention
The present invention provides the process for the preparation of 4-trifluoromethoxyphenol
of Formula I. The present invention also provides the process for the preparation of
intermediates used in preparing 4-trifluoromethoxyphenol.
Background of the invention
4-trifluoromethoxyphenol and its intermediates are extremely useful in pharmaceuticals,
pesticides, dyes, liquid crystal materials and electronic chemicals.
OCF3
OH
Formula I
The U.S Patent No. 3,213,124 describes a process for preparation of ptrifluoromethoxyaniline
by reduction of p-trifluoromethoxynitrobenzene with 5% palladiumon-
charcoal catalyst in the presence of ethanol and hydrogen gas. There are disadvantages,
for example, use of special equipment, inconvenient handling and high cost, associated with
reduction using palladium-on-charcoal. These disadvantages make such processes non-viable
for industrial scale.
While working on present invention, the present inventors, surprisingly, found that ptrifluoromethoxyaniline
of Formula III can be obtained in high yield and purity by using iron
and hydrochloric acid for reduction of p-trifluoromethoxynitrobenzene. Such process is
simple, easy to handle and industrially viable for larger scale production.
Summary of the Invention
The present invention provides a process for the preparation of p-trifluoromethoxyaniline of
Formula III comprising;
a) reacting a compound of Formula II with iron and hydrochloric acid to obtain a
compound of Formula III, and
2
OCF3
NO2
OCF3
NH2
Formula II Formula III
b) isolating the compound of Formula III.
Detailed description of the Invention
The present invention provides a process for the preparation of p-trifluoromethoxyaniline of
Formula III comprising;
a) reacting a compound of Formula II with iron and hydrochloric acid to obtain
compound of Formula III, and
OCF3
NO2
OCF3
NH2
Formula II Formula III
b) isolating the compound of Formula III.
The compound of Formula II may be prepared as per the prior art, for example, U.S Patent
No. 3,213,124. The step a) may take place in the presence of organic solvent. The organic
solvent may be selected from alcoholic solvent. The alcoholic solvent may be selected from
the group consisting of methanol, ethanol, n-propanol, n-butanol, iso-butanol and n-pentanol
or mixture thereof. The hydrochloric acid may be in the form of liquid or gas. The step a)
may take place at a temperature of about 0oC to about 100oC, for example, about 30oC to
about 80oC for about 0.5 hour to about 12 hours, for example, for about 2 hours to about 5
hours.
The compound of Formula III may be isolated by any of the methods in the art, for example,
evaporation, distillation, filtration, decantation, crystallization and layer separation or mixture
thereof.
3
In another aspect, use of compound of Formula III, as prepared by present invention, for the preparation of 4-trifluoromethoxyphenol of Formula I.
The 4-trifluoromethoxyphenol of Formula I, as obtained by present invention, has purity of about 90 % to about 99.5%.
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:
Preparation of p-Trifluoromethoxyaniline
Nitro trifloromethoxybenzene (204 g) was added together with iron (185 g), concentrated HCl (44 ml) in methanol (800 ml) at 600C to 650C. The reaction was stirred and monitored for completion. The iron sludge was filtered off from the reaction mass using celite bed and the filtrate was boiled off. The pH was adjusted to 9-10 to get the desired crude product. The crude product was taken in water and dichloromethane for inorganics removal. The organic layer was extracted and evaporated to obtain the crude title product.
Yield: 155 g
Purity: 88.3%
Preparation of p-Trifluoromethoxyphenol
The 4-(trifloromethoxy) aniline (75 g) was diazotized in 9N H2S04 (750 mL) and aqueous NaNO2 (31 g in 62 mL water) solution at temperature below 5°C.
The formed diazonium salt was decomposed in boiling 9N H2S04 solution (750 mL) at 110°C for 2hrs. The reaction mixture was cooled to 25oC. The bottom layer of reaction mixture was separated. The remaining reaction mixture was extracted with dichloromethane. All organic layers were combined, dried over Na2SO4, filtered and evaporated to obtain the title compound.
Yield: 50 g
Purity: 99.5% 4

We claim:
1. A process for the preparation of p-trifluoromethoxyaniline of Formula III comprising;
a) reacting a compound of Formula II with iron and hydrochloric acid to obtain a
compound of Formula III, and
OCF3
NO2
OCF3
NH2
Formula II Formula III
b) isolating the compound of Formula III.
2. The process of claim 1, wherein step a) takes place in the presence of alcoholic
solvent.
3. The process of claim 2, wherein the alcoholic solvent is selected from the group
consisting of methanol, ethanol, n-propanol, n-butanol, iso-butanol and n-pentanol or
mixture thereof.
4. The process of claim 1, wherein step a) takes place at a temperature in the range of
about 0oC to 100oC.
5. The process of claim 1, wherein the compound of Formula III is isolated by
evaporation, distillation, filtration, decantation, crystallization and layer separation or
mixture thereof.
6. A method of preparing 4-trifluoromethoxyphenol of Formula I by using compound of
Formula III, wherein compound of Formula III is prepared as in claim 1.
7. The method of claim 6, wherein 4-trifluoromethoxyphenol of Formula I so obtained
has purity of about 90 % to about 99.5%.