Process for preparing 4-substituted 2,2,6,6-tetramethylpiperidin-N-oxy and 2,2,6,6-tetramethylpiperidin-N-hydroxy compounds
申请人:Osterholt Clemens
公开号:US20050256312A1
公开(公告)日:2005-11-17
A process 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)
where X+Y can be O or can represent a cyclic ketal with the radicals
or can represent an open-chain ketal in which X═O—R and Y═O—R′, where R and R′ can be identical or different and can each be CH
3
, CH
2
—CH
3
, CH
2
—CH
2
—CH
3
, CH(CH
3
)—CH
3
, CH
2
—CH
2
—CH
2
—CH
3
and CH
2
—CH(CH
3
)—CH
3
,
by oxidizing corresponding 4-substituted 2,2,6,6-tetramethylpiperidines (I)
with 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 acid strength greater than that of the hydrogencarbonate.