Field of the invention
The present invention provides a process for the preparation of cyclic ketones.

Background of the invention
The catalytic hydrogenation of phenols to cyclic ketones is widely known. The EP Publication No. 0,889,019 A1 and EP Publication No. 0,890,565 A1 describe methods for preparing cyclohexanones by hydrogenation of the corresponding phenols in the presence of alkanes or water as solvent. The EP Patent No. 2,607,345 describes a process for preparing cyclohexanones by hydrogenation of the corresponding phenols in the presence of alcohol as solvent.

Summary of the invention
In one aspect, the present invention provides a process for the preparation of a compound of formula II, comprising;
a) contacting a mixture of the compound of formula II and a compound of formula III with hypohalous acid to obtain the compound of formula II, and

Formula III Formula II
b) isolating the compound of formula II obtained from step a).

In second aspect, the present invention provides a process for the preparation of a compound of formula II, comprising;
c) contacting a compound of formula III with hypohalous acid to obtain the compound of formula II, and

Formula III Formula II
d) isolating the compound of formula II obtained from step c).

Detailed description of the invention
The present inventors have observed that hydrogenation of 4-methoxyphenol of Formula I in the presence of hydrogenation catalyst results in the formation of mixture of compound of Formula II and compound of Formula III. The present inventors have surprisingly observed that the complete conversion of mixture of compound of Formula III and compound of Formula II into compound of Formula II can be effectively carried out using hypohalous acid.

Formula I Formula III Formula II

The hypohalous acid used in the step a) and step c) is itself prepared by contacting the trichloroisocyanuric acid with water or by contacting the metal hypochlorite with an organic or inorganic acid or mixture thereof wherein the metal hypochlorite is selected from the group consisting of calcium hypochlorite, sodium hypochlorite and potassium hypochlorite or mixture thereof and the organic acid is selected from the group consisting of formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, chlorodifluoroacetic acid, difluoroacetic acid and trifluoroacetic acid or mixture thereof. The inorganic acid is selected from group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid and hydrobromic acid or mixture thereof.

The reaction of step a) and step c) is carried out in acidic medium at a pH below 7 and at a temperature selected in the range of -20oC to 100oC in the presence or absence of a solvent, wherein the solvent is selected from the group consisting of water, alcohols, ketones, acetonitrile, tetrahydrofuran and dioxane or mixtures thereof.

Preferably the ketones are selected from the group consisting of methyl isobutyl ketone, methyl tertiary butyl ketone and cyclo hexanone or mixture thereof.

The reaction can be carried out in the acidic medium which can be achieved either by addition of the acid to the mixture of compound of Formula II and Formula III followed by the addition of metal hypohalide or both acid and metal hypohalide can be added simultaneously to the mixture of compound of Formula II and Formula III maintaining the acidic reaction mass.

The compound of Formula II is isolated by any method known in the art, for example, chemical separation, acid-base neutralization, distillation, evaporation, column chromatography and filtration or mixture thereof.

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.

The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.

PREPARATION OF 4-METHOXYCYCLOHEXANONE

Example
The mixture of 4-methoxycyclohaxanol and 4-methoxycyclohexanone (100 g) was taken in a round bottomed flask and aqueous sodium hypochlorite (6%w/w, 930gm) was added with continuous stirring at 20oC over the period of 3 hours to 4 hours. The acidic medium was maintained in the reaction mixture with simultaneous addition of concentrated hydrochloric acid. The progress of reaction was monitored by gas chromatography. After completion of the reaction, the excess of hypochlorite was neutralized usingaqueous sodium sulfite solution and the crude product thus obtained wasdistilled to get the title compound.
Yield (%): 90

WE CLAIM:
1. A process for the preparation of a compound of formula II, comprising;
a) contacting a mixture of the compound of formula II and a compound of formula III with hypohalous acid to obtain the compound of formula II, and

Formula III Formula II
b) isolating the compound of formula II obtained from step a).

2. A process for the preparation of a compound of formula II, comprising;
c) contacting a compound of formula III with hypohalous acid to obtain the compound of formula II, and

Formula III Formula II
d) isolating the compound of formula II obtained from step c).

3. The process as claimed in claim1 and 2, wherein the hypohalous acid isfreshly prepared by contacting the trichloroisocyanuric acid with water.

4. The process as claimed in claim 1 and 2, wherein the hypohalous acid is freshly prepared by contacting the metal hypochlorite with an organic or inorganic acid or mixture thereof.

5. The process as claimed in claim4, wherein the metal hypochlorite is selected from the group consisting of calcium hypochlorite, sodium hypochlorite and potassium hypochlorite or mixture thereof.

6. The process as claimed in claim 4, wherein the organic acid is selected from the group consisting of formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, chlorodifluoroacetic acid, difluoroacetic acid and trifluoroacetic acid or mixture thereof.

7. The process as claimed in claim4, wherein the inorganic acid is selected from group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid and hydrobromic acid or mixture thereof.

8. The process as claimed in claim1 and 2, wherein the reaction is carried out in acidic mediumat a pH below 7 and at a temperature in the range of -20oC to 100oCin the presence or absence of solvent.

9. The process as claimed in claim8, wherein the solvent is selected from the group consisting of water, alcohols, ketones, acetonitrile, tetrahydrofuran and dioxane or mixture thereof.

10. The process as claimed in claim 9, wherein the ketones are selected from the
group consisting of methyl isobutyl ketone, methyl tertiary butyl ketone and cyclo hexanone or mixture thereof.