摘要:
A process for purifying crude piperidines of the formula I ##STR1## where R.sup.1 to R.sup.4 are C.sub.1 -C.sub.6 -alkyl, or R.sup.1 and R.sup.2 and/or R.sup.3 and R.sup.4 together are a CH.sub.2 -chain of 2 to 5 carbons, which comprises, in a first step, removing high-boiling substances and, if present, water from the crude piperidines by distillation; in a second step, adding from 0.01 to 5% by weight, based on the product of the first step, as a reducing agent; and, in a third step, isolating the piperidines by distillation.
摘要:
The invention relates to a process for reducing the dimerization of piperidines of the formula I ##STR1## where R.sup.1 to R.sup.4 are C.sub.1 - to C.sub.6 -alkyl, R.sup.1 and R.sup.2 and/or R.sup.3 and R.sup.4 together are a CH.sub.2 chain having 2 to 5 carbon atoms, which comprises adding to the piperidine from 0.001 to 0.2% by weight of a reducing agent of the formula MXH.sub.4-m Y.sub.m, where M is an alkali metal, NR.sub.4, where R are identical or different C.sub.1 -C.sub.4 -alkyl groups, or an equivalent of an alkaline earth metal or an equivalent of zinc, X is boron or aluminum, Y is H or CN and m is 0 or 1. The invention also relates to a mixture of piperidines of the formula I, from 0.001 to 0.2% by weight of a reducing agent and from 1 to 1000 ppm of dimers of the piperidines of the formula I, and to the preparation of hindered amine light stabilizers therefrom.
摘要:
A process for preparing O-alkylated amino alcohols by reacting N-unsubstituted or N-monosubstituted amino alkoxide salts with alkyl halides, the amino alkoxide salts being formed by means of alkali metal or alkaline earth metal hydroxides.
摘要:
The present invention relates to a multi-stage process for producing substituted, optically active alcohols, comprising an enzyme-catalyzed synthesis step, in particular a synthesis step which is catalyzed by an alcohol dehydrogenase. The inventive method is particularly suitable for producing phenylephrine, i.e. 3-[(1R)-1-hydroxy-2-methylamino-ethyl]-phenol.
摘要:
Diastereoselective conversion of chiral imines of the formula I to amines of the formula II where the R1 to R4 radicals are each as defined in the description and R1 and R2 are different than one another, by converting the imine of the formula I in the presence of hydrogen and a heterogeneous copper-containing catalyst.
摘要:
A method for producing 3-pentenenitrile is provided that includes: (a) isomerizing an educt stream containing 2-methyl-3-butenenitrile on at least one dissolved or dispersed isomerisation catalyst to form a stream (1), which contains the isomerisation catalyst(s), 2-methyl-3-butenenitrile, 3-pentenenitrile and (Z)-2-methyl-2-butenenitrile; (b) distilling the stream (1) to obtain a stream (2) as the overhead product, which contains 2-methyl-3-butenenitrile, 3-pentenenitrile and (Z)-2-methyl-2-butenenitrile and a stream (3) as the bottom product, which contains the isomerisation catalyst(s); (c) distilling the stream (2) to obtain a stream (4) as the overhead product, which is enriched with (Z)-2-methyl-2-butenenitrile in comparison to stream (2), and a stream (5) as the bottom product, which is enriched with 3-pentenenitrile and 2-methyl-3-butenenitrile in comparison to stream (2); (d) distilling stream (5) to obtain a stream (6) as the bottom product, which contains 3-pentenenitrile and a stream (7) as the head product containing 2-methyl-3-butenenitrile.
摘要:
The present invention relates to a process for preparing pentamethylene 1,5-diisocyanate, to pentamethylene 1,5-diisocyanate prepared in this way and to the use thereof.
摘要:
The invention provides metal carbamates of the general formula (I) where R1 and R2 are the same or different and are each an alkyl group having 1-18 carbon atoms and M is an alkali metal atom.
摘要:
The invention relates to a process for obtaining a pure aliphatic dialdehyde monoacetal by reaction of the corresponding aliphatic dialdehyde or a precursor of the corresponding aliphatic dialdehyde with one or more aliphatic mono- or polyhydric alcohols while distillatively removing water to obtain a reaction mixture which is separated distillatively, which comprises carrying out the distillative separation continuously in a dividing wall column to obtain pure aliphatic dialdehyde monoacetal as a sidestream from the dividing wall column, or in two distillation columns to obtain crude aliphatic dialdehyde monoacetal as a sidestream in the first distillation column, feed the crude aliphatic dialdehyde monoacetal to the second distillation column and obtain pure aliphatic dialdehyde monoacetal as the sidestream from the second distillation column.