Process for producing 2-phenyl-1,3-benzoxazoles

Patent metadata

Field	Value
Publication number	US-9440935-B2
Application number	US-201414901155-A
Country	US
Kind code	B2
Filing date	Jun 25, 2014
Priority date	Jun 27, 2013
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

The present invention relates to a novel method for producing 2-phenyl-1,3-benzoxazoles of formula (I).

First claim

The invention claimed is:

1. Process for producing 2-phenyl-1,3-benzoxazoles of formula (I),

wherein
R 1 is hydrogen, C 1 -C 6 -alkyl, halogen, OH or OR 2 ; and
R 2 is C 1 -C 6 -alkyl, propargyl or allyl,
said process comprising the steps of
(i) reacting 2-aminophenol (II) with a benzoyl chloride of formula (III) to the amide of formula (IV)

10 followed by
(ii) cyclisation of the amide (IV) to 2-phenyl-1,3-benzoxazol of formula (I),
wherein step (i) is carried out in an inert organic solvent in the presence of at least 0.75 mole-equivalent of sodium hydrogen carbonate or potassium hydrogen carbonate based on the benzoyl chloride of formula (III).

2. A process according to claim 1 , wherein R 1 denotes to a linear C 1 -C 4 -alkyl radical, to OR 2 wherein R 2 is a propargyl or an allyl radical, or to a fluor radical.

3. A process according to claim 2 , wherein R 1 is a fluor radical.

4. A process according to claim 1 , wherein the inert solvent is selected from the group consisting of toluene, xylene, dioxane, tetrahydrofuran or 2-methyl-tetrahydrofurane.

5. A process according to claim 1 , wherein the inert solvent is 2-methyltetrahydrofuran.

6. A process according to claim 1 , wherein the amount of the inert solvent is selected such that the amount of the benzoyl chloride of formula (III) is in the range of 0.001-2 g/ml solvent, preferably in the range of 0.01-1 g/ml solvent, most preferably in the range of 0.1-0.5 g/ml.

7. A process according to claim 1 , wherein the amount of sodium or potassium hydrogen carbonate is selected in the range of 0.75-1.5 mole-equivalents based on the amount of the benzoyl chloride of formula (III).

8. A process according to claim 1 , wherein sodium hydrogen carbonate is used.

9. A process according to claim 1 , wherein the molar ratio of aminophenol (II) to benzoylchloride (III) is selected in the range of 0.75-1.25, such as more preferably in the range of 0.9-1.1.

10. A process according to claim 1 , wherein the amide (IV) is isolated before the cyclisation step.

11. A process according to claim 1 , wherein the cyclization is carried out in toluene or xylene in the presence of an acidic catalyst selected from the group consisting of methanesulfonic acid and/or p-toluenesulfonic acid.

12. A process according to claim 11 , wherein the reaction water formed during the cyclization is removed by azeotrop distillation.

13. A process according to claim 1 , wherein the process comprises after the cyclization step (ii) an additional decolorization step.

14. A process according to claim 13 , wherein the decolorization is done by treatment with activated charcoal.

Assignees

• Dsm Ip Assets Bv

Inventors

• Peng Kun
• Feng Zheng-Chuan

Classifications

• C07D263/57 Primary

  Aryl or substituted aryl radicals · CPC title