Continuous process for preparing indolenine compounds
AssigneePPG Industries, Inc.
InventorsCharles H. Hoelscher, Bruce R. Anderson
Life of this patent
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Abstract
Described is a continuous process for preparing indolenine compounds which comprises charging continuously and simultaneously to a reactor containing an acetic acid reaction medium (1) substituted phenylhydrazine and (2) unsymmetrical ketone from separate sources, continuously discharging from the reactor indolenine product in acetic acid solution, separating acetic acid from the indolenine product, recycling separated acetic acid to the reactor, neutralizing residual acetic acid remaining in the indolenine product with aqueous inorganic alkaline reagent, and separating from the indolenine product an aqueous solution of salts resulting from the preparation and neutralization of the indolenine product.
Claims21
In the method for preparing an indolenine compound by intramolecular condensation of a phenylhydrazine with an unsymmetrical ketone, the improvement which comprises the steps of:
- (a) continuously and simultaneously introducing (1) phenylhydrazine reactant and (2) unsymmetrical ketone reactant from separate sources into a reactor having a reaction medium consisting essentially of organic solvent,
- (b) carrying out said intramolecular condensation in said reaction medium in the presence of a catalyst consisting essentially of a catalytic amount of a weak organic carboxylic acid and at temperatures at which the condensation reaction occurs,
- (c) continuously removing indolenine product from the reactor as a solution in said reaction medium, and
- (d) separating indolenine product from the reaction medium solution thereof removed from the reactor.
In the method for preparing an indolenine compound by intramolecular condensation of a phenylhydrazine with an unsymmetrical ketone, the improvement which comprises the steps of:
- (a) continuously and simultaneously introducing (1) phenylhydrazine reactant and (2) unsymmetrical ketone reactant from separate sources to a reactor having a reaction medium consisting essentially of organic solvent, at temperatures at which the condensation reaction occurs,
- (b) carrying out said intramolecular condensation in said reaction medium in the presence of a catalyst consisting essentially of a catalytic amount of weak organic carboxylic acid,
- (c) continuously removing indolenine product from the reactor as a solution in said reaction medium,
- (d) separating indolenine product from the reaction medium solution removed from the reactor,
- (e) returning to the reactor reaction medium separated from the indolenine product in step (c),
- (f) neutralizing residual organic carboxylic acid remaining in the indolenine product with aqueous inorganic alkaline reagent, and
- (g) separating from the indolenine product of step (f) an aqueous solution of salts resulting from the preparation and neutralization of said product.
Dependencies are inferred from the claim text.