US 2010/0249451 A1 · PROCESS FOR THE PREPARATION OF SUBSTITUTED BENZILIC ACID FROM SUBSTITUTED BENZILS

Abstract

The classical process for the rearrangement of substituted benzil to benzilic acid is performed in the presence of sodium or potassium hydroxide as a base using ethanol-ether as a medium. The reaction requires reflux temperature for complete conversion. However, these bases containing metallic ions and generate metallic containing effluent waste which may require additional expenditure for treatment. Moreover, because of corrosive nature of base, and use of flammable solvent, the safety measures are needed during large scale production. Another method also reported for benzilic acid rearrangement at 380° C. which is practically not feasible. The present invention describes the use of quaternary ammonium hydroxides as a base for the rearrangement of the substituted benzils to benzilc acids. It also avoids the use of solvent and reaction can be carried out at relatively lower temperatures. Because of the solvent free reaction condition it reduces the mass/volume of reaction mixture.

Claims10

Dependent claims

An improved process for the preparation of substituted benzilic acid of formula 3

wherein R1 and R2 are selected from the group consisting of hydrogen, halogen(F, Cl, Br, I), alkyl (C1-C4), alkoxy (C1-C8) or nitro, wherein the said process comprising of:
a. stirring a mixture of substituted benzil of formula 1
wherein R1 and R2 are selected from the group consisting of hydrogen, halogen, alkyl , alkoxy or nitro and quaternary ammonium hydroxide of formula 2
wherein R3, R4, R5, R6 may be alkyl (C1-C5), aralkyl or combination thereof at temperature ranging between 20° C. to 80° C., preferably 40° C. to 70° C. for a period ranging between 1 to 6 hrs, preferably 2 to 4 hrs;
b. diluting the reaction mixture as obtained in step (a) with water;
c. acidifying the reaction mixture as obtained in step (b) to pH ranging between 2 to 3.5 with dilute hydrochloric acid;
d. filtering and washing the solid as obtained in step (c) with water to obtained substituted benzilic acid, yield in the range of 85 to 95%.

4 more elements

Dependencies are inferred from the claim text.

Process for the preparation of substituted benzilic acid from substituted benzils

Life of this patent

Process for the preparation of substituted benzilic acid from substituted benzils

Life of this patent

Abstract

Claims10