The present invention provides a process for preparation of substituted alkanols.

BACKGROUND OF THE INVENTION
Substituted alkanols like fluorinated alcohol are useful as solvent for preparing a photoreceptor for a film or a recording layer for an information recording medium (such as an optical disk such as CD-R or DVD-R) capable of writing and/or reading information by a laser formed on a substrate.
Various methods are known in the art for preparation of substituted alkanols e.g., EP Patent Pub. No. 968989 provides a process for producing 2,2,3,3-tetrafluoro-1-propanol by reacting methanol with tetrafluoroethylene or hexafluoropropylene in the presence of an initiator at a pressure of about 0.2-1.2 MPa (2 to 12 Kg/cm2) and distilling the product after decomposing the remaining initiator contained in the reaction mixture.
EP Patent Pub. No. 967193 provides a method for producing tetrafluoropropanol by reacting methanol with tetrafluoroethylene or hexafluoropropylene in the presence of a free radical source at a pressure of about 0.2-1.2 MPa (2 to 12 Kg/cm2) and distilling the product in presence of a base.
The main disadvantage of the above processes is that these are carried out at very high-pressure range, which are not commercially viable. Thus, there is a need to develop an alternative process for preparation of substituted alkanols.
Surprisingly, the inventors of the present invention found that substituted alkanols can be prepared in good yield at a low pressure range and by using radical initiator’s quantity in a specific range.

OBJECT OF THE INVENTION
The object of the present invention is to provide an alternative and cost effective process for preparation of a compound of formula 1,

Formula 1
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl, fluoromethyl n is any number selected from 1 to 10.

SUMMARY OF THE INVENTION
In an aspect, the present invention provides a process for preparation of a compound of formula 1,

Formula 1
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl; and n is any number selected from 1 to 10,
comprising the steps of reacting a compound of formula 2,

Formula 2
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl,
with C1-10 alkanols in presence of a radical initiator to obtain the compound of formula 1, wherein the step a) is carried out at a pressure selected in the range of 0 to 2Kg/cm2.
In another aspect, the present invention provides a process for preparation of a compound of formula 1,

Formula 1
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl; and n is any number selected from 1 to 10,
comprising the steps of:
a) reacting a compound of formula 2,

Formula 2
with C1-10 alkanol in presence of a radical initiator to obtain the compound of formula 1, wherein radical initiator is added in a range of 2 to 6% w/w with respect to the alkanols.

DETAILED DESCRIPTION OF THE INVENTION
As used herein, fluoromethyl is selected from monofluoromethyl, difluoromethyl and trifluoromethyl. It is preferred that only one of the R1, R2, R3 and R4 is fluoromethyl.
As used herein, the radical initiator is a peroxide of the following formula 3.

R5—O—O—Y—R6
Formula 3
wherein Y is a carbon or a keto group. R5 is a C1—20 aliphatic hydrocarbon group, and R6 is a C1—20 aliphatic hydrocarbon group, or an aromatic hydrocarbon group.
Specific examples of the alkyl peroxide of the formula 3 include di-tert-butyl peroxide, tert-butyl peroxy-2-ethyl hexanoate, tert-butyl peroxy isopropyl carbonate and tert-butyl cumyl peroxide. Among them, tert-butyl peroxy-2-ethyl hexanoate is most preferred radical initiator used in the present invention.
Further UV radiations, heat, an azo type initiator or a photo radical initiator may be used in combination with the peroxide.
The C1—20 aliphatic hydrocarbon group is preferably an aliphatic saturated hydrocarbon group, which may, for example, be an alkyl group, a cycloalkyl group or a cycloalkylaryl group, and particularly preferred is an alkyl group. Further, the aromatic hydrocarbon group may, for example, be a phenyl group or a phenyl group having a substituent.
In another embodiment, C1-10 alkanol is selected in a range of 8 to 13 mole equivalent with respect to compound of formula 2. In a preferred embodiment, 12 mole equivalents of C1-10 alkanol are used.
In an embodiment, the reaction of compound of formula 2 with C1-10 alkanol is carried out at a pressure range of 0.5 kg/cm2 to 1.5kg/cm2.
In an embodiment the reaction is carried out at a temperature selected in the range of 40 to 60°C.
The process of the present invention is either a batch process or a continuous process. In a batch process, the unreacted compound of formula 2 is quenched using bromine scrubber at a temperature selected in the range of 0 to 30°C. In a continuous process, the unreacted compound of formula 2 is recycled back to the reactor.
As used herein, bromine is selected in a range of 0.3 to 0.9 mole equivalents with respect to compound of formula 2. In a preferred embodiment, 0.5 equivalents of bromine are used.
In an embodiment, the reaction mass was flushed with nitrogen gas for at least 10 to 15 minutes at a temperature selected in the range of 40 to 60°C before purging of compound of formula 2.
The compound of formula 1 as prepared by the process of the present invention has a selectivity of at least 90%, which tends to maximum conversion of reactant into desired product which also results in very high yield.
In an embodiment, the compound of formula 1 as prepared by the process of the present invention has a selectivity in the range of 90 to 98%.
In an embodiment, the compound of formula 1 is obtained with a dimer impurity of below 2.5%,

Dimer impurity
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl; and n is any number selected from 1 to 10.
In another embodiment, the compound of formula 1 is obtained with a dimer impurity below 1.0%. In still another embodiment, the compound of formula 1 is obtained with a dimer impurity below 0.1%.
In an embodiment, the compound of formula 1 is obtained with a dimer impurity in the range of 0.1 to 2.5%.
In an embodiment, the compound of formula 1 is obtained with a trimer impurity below 1%,

Trimer impurity
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl.
In another embodiment, the compound of formula 1 is obtained with a trimer impurity below 0.05%.
In an embodiment, the compound of formula 1 is obtained with a trimer impurity in the range of 0 to 1%.
In an embodiment, the compound of formula 1 is obtained with a purity of at least 95%. In another embodiment, the compound of formula 1 is obtained with a purity of at least 97%. In still another embodiment, the compound of formula 1 is obtained with a purity of at least 99%.
In an embodiment, the compound of formula 1 is obtained with a purity in the range of 95% to 99%.
In an embodiment, the compound of formula 1 is obtained with a yield of at least 41%. In another embodiment, the compound of formula 1 is obtained with a yield of at least 75%. In still another embodiment, the compound of formula 1 is obtained with a yield of at least 90%.
In an embodiment, the compound of formula 1 is obtained with a yield in the range of 41% to 90%.
The reaction of compound of formula 2 with C1-10 alkanol was carried out by maintaining radical initiator content in a range selected from 2 to 6% w/w with respect to the C1-10 alkanol. The radical initiator content was analysed by titration in every eight hours. In a preferred embodiment, the radical initiator content was selected in a range of 3 to 4% w/w with respect to the C1-10 alkanol.
After reaction completion, the reaction mass was cooled to 30°C and unloaded from the reactor.
In an embodiment the isolation of compound of formula 1 from step a reaction mixture is performed using distillation at reduced pressure (300mmHg to 40 mm Hg) at 55-60°C.
In another embodiment, the isolation of compound of formula 1 from step a reaction mixture is performed using distillation at reduced pressure (300mmHg to 40 mm Hg) at 55-60°C followed by drying to remove excess water.
In an embodiment, sodium sulphate, calcium sulphate, calcium chloride, silica, alumina or calcium oxide is used to remove moisture.
In an embodiment, the moisture content after drying is in the range of 0.01 to 0.5% w/w.
In an embodiment, distillation is performed without using any decomposing agents such as acid catalyst, reducing agent, UV irradiation or a base.
As used herein, the term “isolating” refers to the method used to isolate the compound from the reaction mixture. The isolation is carried out using any of the process consisting of extraction, distillation, filtration, decantation, washing, dryings or combination thereof.
The completion of the reaction is monitored by gas chromatography (GC).
Unless stated to the contrary, any of the words “comprising”, “comprises” and includes mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The compound of formula 2 which is used herein as starting material can be prepared by any of the methods known in the art i.e., or can be obtained commercially.
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.

EXAMPLES
Example 1: Tert-butylperoxy-2-ethyl hexanoate (3.8g) and methanol (242g) were charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 1.5 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the unreacted tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 75%; Purity: 94% (by GC area)
Example 2: Tert-butylperoxy-2-ethyl hexanoate (3.8g) and methanol (242g) were charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 1 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the unreacted tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 78%; Purity: 96% (by GC area)
Example 3: Tert-butylperoxy-2-ethyl hexanoate (3.8g) and methanol (242g) were charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 0.5 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the unreacted tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 78%; Purity: 99% (by GC area)
Example 4: Tert-butylperoxy-2-ethyl hexanoate (9.67g) and methanol (242g) were charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 1.5 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the excess of tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 75%; Purity: 97% (by GC area)

Example 5: Tert-butylperoxy-2-ethyl hexanoate (11.67g) as radical initiator and methanol (242g) was charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 1 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the excess of tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 78%; Purity: 98% (by GC area)
Example 6: Tert-butylperoxy-2-ethyl hexanoate (12.68g) as radical initiator and methanol (242g) was charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 0.5 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the excess of tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 80%; Purity: 99% (by GC area)
Example 7: Di-tert-butyl peroxide (12.68g) as radical initiator and methanol (242g) was charged in an autoclave. The reaction mass was heated to 40 to 60°C and flushed with nitrogen gas for 10 to 15 minutes. Tetrafluoroethylene (TFE) gas was purged into the reaction mass at 40 to 60°C and at pressure of 0.5 Kg/cm2. Progress of the reaction was monitored by GC analysis. After reaction completion, the excess of tetrafluoroethylene was recycled back to the autoclave. The reaction mass containing 2,2,3,3-tetrafluoro-1-propanol was then cooled to 30°C and unloaded from the reactor. The unloaded mass was taken for product isolation by distillation and pure product was dried subsequently to obtain the title compound.
Yield: 82%; Purity: 98% (by GC area)

CLAIMS:WE CLAIM:
1. A process for preparation of a compound of formula 1,

Formula 1
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl; and n is any number selected from 1 to 10,
comprising the steps of reacting a compound of formula 2,

Formula 2
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl,
with C1-10 alkanols in presence of a radical initiator to obtain the compound of formula 1, wherein the step a) is carried out at a pressure selected in the range of 0 to 2Kg/cm2.
2. A process for preparation of a compound of formula 1,

Formula 1
wherein R1, R2, R3 and R4 is selected independently from fluorine, hydrogen, methyl and fluoromethyl; and n is any number selected from 1 to 10,
comprising the steps of reacting a compound of formula 2,

Formula 2
with C1-10 alkanol in presence of a radical initiator to obtain the compound of formula 1, wherein the quantity of radical initiator is maintained in a range of 2 to 6% w/w with respect to the alkanols.
3. The process as claimed in claim 1 and claim 2, wherein the radical initiator is a peroxide of the formula 3.
R5—O—O—Y—R6
Formula 3
wherein Y is a carbon or a keto group. R5 is a C1—20 aliphatic hydrocarbon group, and R6 is a C1—20 aliphatic hydrocarbon group, or an aromatic hydrocarbon group.
4. The process as claimed in claim 1 and 2, wherein the reaction is carried out at a temperature selected in the range of 40 to 60°C.
5. The process as claimed in claim 1 and 2, wherein the isolation of compound of formula 1 from step a reaction mixture is performed using distillation at a pressure in the range of 300mmHg to 40 mmHg at 55-60°C.
6. The process as claimed in claim 1 and 2, wherein the C1-10 alkanol is selected in a range of 8 to 13 mole equivalent with respect to compound of formula 2.
7. The process as claimed in claim 1 and 2, wherein the compound of formula 1 is obtained with a selectivity in the range of 90 to 98%.
8. The process as claimed in claim 1 and 2, wherein the compound of formula 1 is obtained with a dimer impurity in the range of 0.1 to 2.5% and trimer impurity in the range of 0 to 1%.
9. The process as claimed in claim 1 and 2, wherein reaction is carried out at a pressure selected in the range of 0.5 kg/cm2 to 1.5 kg/cm2.
10. The process as claimed in claim 1 and 2, wherein the radical initiator content is maintained in a range of 3 to 4% w/w with respect to the C1-10 alkanol.