摘要:
Process for preparing N-pyruvyl-L-proline by reaction of L-proline with methyl pyruvate dimethyl ketal in the presence of an alkali metal alkoxide, subsequent acid hydrolysis and extraction of 1-pyruvyl-L-proline.
摘要:
A method for producing aqueous ortho-phthalaldehyde solutions which comprises introducing an acetal of the o-phthalaldehyde into water and subsequently setting a pH
摘要:
The invention relates to a method for producing hydroxymethylpyridines from the corresponding vinylpyridines by means of ozonisation in an alcohol as solvent and by means of hydrogenation of the peroxide-containing solution produced thereby, in the presence of a hydrogenation catalyst The hydrogenation solution is adjusted to a pH value of 10 to 14 by adding a base and the alcohol is distilled off and the desired hydroxymethylpyridine is isolated in high purity by extracting with an organic solvent and by means of subsequent distillative purification.
摘要:
A method for producing aqueous ortho-phthalaldehyde solutions which comprises introducing an acetal of the o-phthalaldehyde into water and subsequently setting a pH
摘要:
Improved process for preparing high-purity, halogen-free o-phthalaldehyde, in which a) tetrahalo-o-xylene is hydrolyzed at a temperature of 155-160° C. and a pressure of from 2 to 5 bar, where appropriate in the presence of a phase-transfer catalyst, to o-phthalaldehyde, which b) is converted in an acidic alcoholic solution at a temperature of from 0 to the reflux temperature into the corresponding dialkoxyphthalane and, subsequently, c) an acetal cleavage is effected by acid hydrolysis at a pH >1.5 to pH 7, resulting in high-purity, halogen-free o-phthalaldehyde.
摘要:
Improved, safe process for the purification of ketones obtained by ozonolysis and subsequent reduction of the corresponding terpenes, in which, after the ozonolysis and reduction of acyclic mono-, bi- or tricyclic terpenes with ozonizable double bonds, converting the resulting corresponding crude ketone into a high-purity ketone by means of steam distillation at atmospheric pressure or at reduced pressure, extraction of the steam distillate and subsequent distillation.
摘要:
Improved process for the purification and formulation of o-phthalaldehyde in which crude o-phthalaldehyde, obtained by cleavage of an acetal of o-phthalaldehyde by means of acidic hydrolysis, is, optionally by adding an aqueous basic solution, adjusted to a pH of from 1 to 8, and then, after phase separation has taken place, water is distilled off from the phase which contains the aldehyde with very short thermal stress of less than 1 minute at a pressure of between 100 mbar and atmospheric pressure and a temperature of from room temperature to 180° C. on a thin-layer overhead evaporator and o-phthalaldehyde is then stripped off from the distillation bottom which remains with very short thermal stress of less than 1 minute at a pressure of from 0.5 to 50 mbar and a jacket temperature of from 80 to 80° C. via a thin-layer evaporator and the resulting o-phthalaldehyde melt is pelleted at atmospheric pressure and a temperature of from 60 to 80° C., giving pale yellow o-phthalaldehyde in high purity and storage-stable form.
摘要:
Improved process for preparing high-purity, halogen-free o-phthalaldehyde, in which a) tetrahalo-o-xylene is hydrolyzed at a temperature of 155-160° C. and a pressure of from 2 to 5 bar, where appropriate in the presence of a phase-transfer catalyst, to o-phthalaldehyde, which b) is converted in an acidic alcoholic solution at a temperature of from 0 to the reflux temperature into the corresponding dialkoxyphthalane and, subsequently, c) an acetal cleavage is effected by acid hydrolysis at a pH >1.5 to pH 7, resulting in high-purity, halogen-free o-phthalaldehyde.
摘要:
A process for preparing substituted aromatic and heteroaromatic aldehydes or carboxylic acids of the formula in which R1 and R2 are H, C1-C4 alkyl, C1-C4 alkoxy, OH, NO2, CN, COOH, CONH2, COOR, NH2, SO3H or halogen and R is C1-C4 alkyl and where R1 and R2 are not simultaneously H, X is C or N and Z is CHO or COOH, from the corresponding symmetric stilbene compounds of the formula in which R1, R2 and X are as defined above, by aqueous ozonolysis and subsequent isolation of an aldehyde or oxidation to give the corresponding carboxylic acid.
摘要:
Process for the preparation of pure 2,3-pyridinedicarboxylic acids of the formula I which are substituted in position 4 and/or 5 and/or 6 by R1, where R1 is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkoxy-C1-C4 alkyl, halogen, hydroxyl or nitro, from quinolines of the formula II in which R1 is as defined above, and which are substituted in position 6 and/or 7 by R2, where R2 is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkoxy-C1-C4 alkyl, halogen, hydroxyl, nitro or amino, which are reacted in the first step in aqueous sulfuric acid or nitric acid solution with ozone in the ratio of from 1:2 to 1:3 at temperatures from 0 to +50° C., and the resulting peroxide solution is then reacted at temperatures of from +0 to +100° C. in the presence of 0.5-4.0 mol of oxidizing agent per mole of ozonolysis product formed, after which the pH of the reaction solution is adjusted to 0.2 to 3, the mixture is cooled to 0 to 30° C., and the precipitated pyridinedicarboxylic acid is isolated.