GB2051068A - Dehydrogenation of 2- alkoxycyclohexanols - Google Patents

Abstract

A method of preparing an ortho- alkoxyphenol, comprises dehydrogenating a 2- alkoxycyclohexanol over a palladium catalyst in the liquid or vapour phase and in the presence of sulphur and sodium carbonate.

Description

SPECIFICATION Dehydrogenation of 2-alkoxycyclohexanols The present invention relates to dehydrogenation of 2-alkoxycyclo-hexanols to the corresponding ortho-alkoxyphenols.

According to the present invention, there is provided a method of preparing an orthoalkoxyphenol, comprising dehydrogenating a 2alkoxycyclohexanol over a palladium catalyst in the liquid or vapour phase and in the presence of sulphur and sodium carbonate. The dehydrogenation may be represented by the following equation:

where R is a substituted alkyl group. The alkyl group may have, for example, up to twelve carbon atoms and may be a straight chain group or a cycloalkyl group. The alkyl group may be a primary, secondary or tertiary alkyl group.

In particular R may be an isopropyl group, the ortho-alkoxyphenol (or catechol monoether) produced being o-isopropoxyphenol, which is useful in the manufacture of the compound which is used as a pesticide and is an active ingredient of the pesticidal composition "Baygon" and the pesticidal composition "Propoxur".

The invention is illustrated by the following examples.

EXAMPLE 1 A mixture of 2-isopropoxycyclohexanol and diphenyl was introduced into a reaction vessel.

Then a palladium-on-carbon (porous charcoal) catalyst comprising 3% by weight palladium was added to the reaction vessel. Then a solution of diphenyl sulphide in further of the 2-isopropoxy cyclohexanol was added to the reaction vessel, followed by powered sodium carbonate (anhydrous). In the resulting reaction system, the volume ratio of 2-isopropoxy cyclohexanol to diphenyl was 1: 1, the concentration of sulphur (as diphenyl sulphide) was 1 8 ppm, and the concentration of Na2CO3 was 1% by weight. The reaction system was refluxed (at 21 0-2200C) whilst a stream of nitrogen was passed through the system. When hydrogen ceased to be produced (after 25 hours) the reaction system was cooled and treated with an aqueous solution of sodium hydroxide to extract a product comprising isopropoxyphenol.This product consisted of (by weight): Isopropoxyphenol 95.5% Phenol 3.8% Catechol 0.7% The isopropoxyphenol was produced in a yield of about 72.5% based on the isopropoxy cyclohexanol.

EXAMPLE 2 Example 1 was repeated, the concentration of sulphur (as diphenyl sulphide) in the reaction system being 24 ppm and production of hydrogen ceasing after refluxing of the reaction system for 21 hours, all other conditions being the same as previously described.

The product consisted of (by weight): Phenol 1.4% Catechol 0.4% Diphenyl 0.2% 2-isopropoxycyclohexanol 0.2% The isopropoxyphenol was produced in a yield of 83% based on the isopropoxy cyclohexanol.

In the examples above, it is envisaged that the isopropoxyphenol could have been separated from the reaction system by distillation since substantially no impurities are produced as byproducts.

1. A method of preparing an orthoalkoxyphenol, comprising dehydrogenating a 2alkoxycyclohexanol over a palladium catalyst in the liquid or vapour phase and in the presence of sulphur and sodium carbonate.

2. A method according to claim 1, wherein the dehydrogenation is carried out in the liquid phase.

3. A method according to either preceding claim, wherein the 2-alkoxycyclohexanol is 2isopropoxycyclohexanol.

4. A method according to any preceding claim, wherein the palladium is present as palladium-oncarbon.

5. A method according to any preceding claim, wherein the sulphur is present as a sulphur compound.

6. A method according to claim 5, where the sulphur is present as diphenyl sulphide.

7. A method according to either preceding claim, substantially as described herein in either of the examples.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Dehydrogenation of 2-alkoxycyclohexanols The present invention relates to dehydrogenation of 2-alkoxycyclo-hexanols to the corresponding ortho-alkoxyphenols. According to the present invention, there is provided a method of preparing an orthoalkoxyphenol, comprising dehydrogenating a 2alkoxycyclohexanol over a palladium catalyst in the liquid or vapour phase and in the presence of sulphur and sodium carbonate. The dehydrogenation may be represented by the following equation: where R is a substituted alkyl group. The alkyl group may have, for example, up to twelve carbon atoms and may be a straight chain group or a cycloalkyl group. The alkyl group may be a primary, secondary or tertiary alkyl group. In particular R may be an isopropyl group, the ortho-alkoxyphenol (or catechol monoether) produced being o-isopropoxyphenol, which is useful in the manufacture of the compound which is used as a pesticide and is an active ingredient of the pesticidal composition "Baygon" and the pesticidal composition "Propoxur". The invention is illustrated by the following examples. EXAMPLE 1 A mixture of 2-isopropoxycyclohexanol and diphenyl was introduced into a reaction vessel. Then a palladium-on-carbon (porous charcoal) catalyst comprising 3% by weight palladium was added to the reaction vessel. Then a solution of diphenyl sulphide in further of the 2-isopropoxy cyclohexanol was added to the reaction vessel, followed by powered sodium carbonate (anhydrous). In the resulting reaction system, the volume ratio of 2-isopropoxy cyclohexanol to diphenyl was 1: 1, the concentration of sulphur (as diphenyl sulphide) was 1 8 ppm, and the concentration of Na2CO3 was 1% by weight. The reaction system was refluxed (at 21 0-2200C) whilst a stream of nitrogen was passed through the system. When hydrogen ceased to be produced (after 25 hours) the reaction system was cooled and treated with an aqueous solution of sodium hydroxide to extract a product comprising isopropoxyphenol.This product consisted of (by weight): Isopropoxyphenol 95.5% Phenol 3.8% Catechol 0.7% The isopropoxyphenol was produced in a yield of about 72.5% based on the isopropoxy cyclohexanol. EXAMPLE 2 Example 1 was repeated, the concentration of sulphur (as diphenyl sulphide) in the reaction system being 24 ppm and production of hydrogen ceasing after refluxing of the reaction system for 21 hours, all other conditions being the same as previously described. The product consisted of (by weight): Phenol 1.4% Catechol 0.4% Diphenyl 0.2% 2-isopropoxycyclohexanol 0.2% The isopropoxyphenol was produced in a yield of 83% based on the isopropoxy cyclohexanol. In the examples above, it is envisaged that the isopropoxyphenol could have been separated from the reaction system by distillation since substantially no impurities are produced as byproducts. CLAIMS

1. A method of preparing an orthoalkoxyphenol, comprising dehydrogenating a 2alkoxycyclohexanol over a palladium catalyst in the liquid or vapour phase and in the presence of sulphur and sodium carbonate.

2. A method according to claim 1, wherein the dehydrogenation is carried out in the liquid phase.

3. A method according to either preceding claim, wherein the 2-alkoxycyclohexanol is 2isopropoxycyclohexanol.

4. A method according to any preceding claim, wherein the palladium is present as palladium-oncarbon.

5. A method according to any preceding claim, wherein the sulphur is present as a sulphur compound.

6. A method according to claim 5, where the sulphur is present as diphenyl sulphide.

7. A method according to either preceding claim, substantially as described herein in either of the examples.