| 摘要 |
The present invention relates to processes for preparing 4-substituted 2,2,6,6-tetramethylpiperidin-N-oxy compounds [II] or mixtures of [II] and 4- substituted 2,2,6,6-tetramethylpiperidin-N-hydroxy compounds [III] <IMG> where X+Y can be O or can represent a cyclic ketal with the radicals <IMG> or can represent an open-chain ketal in which X= O-R and Y= O-R', where R an d R' can be identical or different and can each be CH3, CH2-CH3, CH2-CH2-CH3, CH(CH3)-CH 3, CH2-CH2-CH2-CH3 and CH2-CH(CH3)-CH3, by oxidizing corresponding 4-substituted 2,2,6,6-tetramethylpiperidines [I] <IMG> by means of hydrogen peroxide in the presence of alkali metal hydrogencarbonate and/or ammonium hydrogencarbonate and in the presence or absence of a solvent, in which the reaction is carried out with the addition of Brönsted acids which have an ac id strength greater than that of the hydrogencarbonate used.
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