| 摘要 |
1. A process for preparing glyoxylic esters, characterized in that a glyoxylic ester hemiacetal is a) transesterifying directly with an alcohol in the presence of a catalyst, or b) first converting into the corresponding glyoxylic ester acetal and then transesterifying it with an alcohol in the presence of a catalyst, whereupon, following a) and b), the acetal is cleaved to give the desired free glyoxylic ester or its hydrate. 2. The process as claimed in claim 1, characterized in that the glyoxylic acid ester hemiacetals used are glyoxylic acid methyl ester, ethyl ester, n-propyl ester, isopropyl ester, or t- or n-butyl ester hemiacetals. 3. The process as claimed in claim 1, characterized in that the conversion to the complete acetal is performed using a liquid or vaporous alcohol selected from the group consisting of methanol, ethanol, propanol, butanol and hexanol in the presence of an acid as catalyst. 4. The process as claimed in claim 1, characterized in that the transesterification is performed using a chiral or non-chiral, primary, secondary or tertiary alcohol. 5. The process as claimed in claim 4, characterized in that the alcohol used is an acyclic, monocyclic, bicyclic terpene alcohol, an acyclic, monocyclic or tricyclic sesquiterpene alcohol, di- or triterpene alcohol. 6. The process as claimed in claim 1, characterized in that the catalyst used is a stannic ester, titanic ester or zirconic ester, a lithium compound or, the basic catalyst used is an alkali metal compound, alkaline earth metal compound or aluminum compound. 7. The process as claimed in claim 6, characterized in that the catalyst used is dialkyltin dicarboxylate having 1-12 carbon atoms in the alkyl moiety, titanium(IV)ethanolate, -iso- or -n- propanolate, -n- or -iso-butanolate or butyllithium. 8. The process as claimed in claim 1, characterized in that the acetal is cleaved by acid catalysis in the presence of H2SO4, p-toluenesulfonic acid, formic acid or acetic acid, or in the presence of a lanthanide catalyst. 9. The process as claimed in claim 8, characterized in that the acetal is cleaved by brief heating of the acetal for up to 1 hour up to boiling point with formic acid, removal of the formate formed and rapid cooling, whereupon the product is crystallized out of a diluent, if appropriate after previous extraction of impurities with water, and isolated.
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