Process for preparing bis-alkoxy-triazinyl-amino-containing...

Details Process for preparing bis-alkoxy-triazinyl-amino-containing... Process for preparing bis-alkoxy-triazinyl-amino-containing...

1998-05-21

2001-06-19

Shah, Mukund J. (Department: 1611)

Organic compounds -- part of the class 532-570 series

Organic compounds

Four or more ring nitrogens in the bicyclo ring system

Reexamination Certificate

active

06248887

ABSTRACT:

The invention relates to a process for the preparation of stilbene-disulphonic acids containing bis-alkoxy-triazinyl-amino, or derivatives thereof, and to their use as optical brighteners for organic material, chiefly for paper and cellulose, in particular for photographic paper. Optical brighteners based on substituted bis-triazinylamino-stilbene-2,2′-disulphonic acids in which in each case each triazine radical is substituted by an alkoxy radical, in addition to the substitution by the flavonic acid and a further amine, and a process for their preparation are known in large numbers.
The alkoxy radical is usually introduced only in the first or in the second stage in the presence of an acid-binding agent. Thus, an alkanol is reacted with cyanuric chloride or with a cyanuric chloride derivative which still contains two chlorine atoms. Considerable undesirable side reactions due to multiple reactions on the cyanuric chloride occur here. Introduction of an alkoxy group in the third stage, i.e. into a cyanuric chloride derivative which still contains only one chlorine atom, requires special conditions, such as, for example, working in anhydrous glycols or glycol monoalkyl ethers in the presence of the corresponding sodium alcoholate (DE-A 1 444 015).
In JP-A 305 983, bis-triazinylamino-stilbene-2,2′-disulphonic acid derivatives are reacted with methanol in a ratio of 1:2 or with a slight excess of methanol.
DE-A-2 335 570 reports that if glycols or glycol monoalkyl ethers are used, it is possible to react these with bis-triazinylamino-stilbene-2,2′-disulphonic acid derivatives, i.e. with a cyanuric chloride derivative which still carries only one chlorine atom on each triazine ring, in the third stage. However, the yield of this procedure is only between 50 and 80% and therefore makes the process unattractive. There was thus a need for a process with which exactly one C
1
-C
4
-alkoxy radical per cyanuric chloride unit can be incorporated selectively and with improved yields into bis-triazinylamino-stilbene-2,2′-disulphonic acids without the use of sophisticated and expensive reagents.
A process has now been found for the preparation of stilbene-disulphonic acids containing bis-alkoxy-triazinyl-amino, or derivatives thereof, in which stilbene-disulphonic acids containing bis-chloro-triazinyl-amino are reacted with a C
1
-C
4
-monoalkanol, characterized in that at least 10 mol of C
1
-C
4
-monoalkanol are employed per mol of the stilbene-disulphonic acid containing bis-chloro-triazinyl-amino, or derivatives thereof.
In a preferred embodiment, at least 20 mol of the C
1
-C
4
-monoalkanol are employed per mol of a stilbene-disulphonic acid containing bis-chloro-triazinyl-amino, or derivatives thereof. Particularly preferably, 50-500 mol, in particular 100-300 mol, of C
1
-C
4
-monoalkanol are employed per mol of stilbene-sulphonic acid compound containing bis-chloro-triazinyl-amino.
In an embodiment which is also preferred, the C
1
-C
4
-monoalkanol is employed together with water, the water content of the reaction mixture preferably being 10-80% by weight, preferably 25-60% by weight, based on the reaction mixture.
Methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol or tert-butanol, in particular methanol, are employed as preferred C
1
-C
4
-monoalkanols. The process for the preparation of 4,4′-bis[6-alkoxy-1,3,5-triazin-2-yl-amino]stilbene-2,2′-disulphonic acid, or derivatives thereof, in which the triazinyl radicals are in each case substituted with amine radicals in the 4-position, is particularly preferred.
The process according to the invention is preferably carried out in the presence of an acid-binding agent, an alkali metal hydroxide, in particular potassium hydroxide or sodium hydroxide, preferably being used as the acid-binding agent. The acid-binding agent is preferably employed in an amount of 2 to 6 molar equivalents per mol of the stilbene-disulphonic acid containing bis-chloro-triazinyl-amino, or derivatives thereof, preferably in an amount of 3 to 4 molar equivalents.
The process according to the invention is as a rule carried out at temperatures from 0C up to the boiling point of the reaction mixture, preferably at 15 to 80° C. In a preferred embodiment of the process according to the invention, compounds of the general formula (I)
wherein
M represents hydrogen, an alkali metal ion or an optionally substituted ammonium ion,
R
1
and R
2
independently of one another denote C
1
-C
4
-alkyl and
R
3
and R
4
independently of one another represent an amine radical,
are prepared.
The preferred compounds of the formula (I) prepared by the process according to the invention are obtained by reaction of compounds of the formula (II)
wherein
R
3
, R
4
and M have the abovementioned meanings,
with C
1
-C
4
-monoalkanols.
Compounds of the formula (II) are obtained, for example, by reaction of 2 equivalents of cyanuric chloride with one equivalent of a compound of the formula (III)
and a total of 2 equivalents of the compounds R
3
H and R
4
H in any desired sequence.
The process according to the invention in which the compounds of the formula (II) are not intermediately isolated after their preparation is preferred. It is particularly preferable here to employ the compound of the formula (II) in the preparation process according to the invention in the form of its aqueous reaction solution, if appropriate after concentration and if appropriate (partial) desalination.
In another preferred embodiment of the process according to the invention, the compounds of the formula (I) are obtained starting from a compound of the formula (II) wherein R
3
and R
4
independently of one another represent NR
5
R
6
, wherein R
5
represents hydrogen or optionally substituted C
1
-C
6
-alkyl and R
6
can assume the meanings given under R
5
or denotes optionally substituted C
1
-C
8
-cycloalkyl or optionally substituted C
6
-C
10
-aryl, or NR
5
R
6
represents optionally C
1
-C
4
-alkyl-, in particular methyl-substituted, morpholino, piperidino or hexamethylene-imino.
Preferred substituents of the C
1
-C
6
-alkyl radical in the meaning of R
5
and R
6
are, for example, hydroxyl, C
1
-C
6
-alkoxy, C
2
-C
8
-alkoxy-substituted C
2
-C
2
-alkoxy, C
1
-C
6
-alkylamino or C
1
-C
6
-dialkylamino, cyano or sulphonic acid or sulphonate.
Preferred substituents of the C
5
-C
8
-cycloalkyl are: halogen, in particular fluorine, chlorine and bromine, C
1
-C
6
-alkyl, C
1
-C
6
-alkoxy, sulphamoyl or sulphonyl, in particular C
1
-C
4
-alkyl.
Possible optionally substituted C
6
-C
10
-aryl is, in particular, sulpho-substituted phenyl.
Especially preferably, R
5
represents hydrogen, methyl, sulphoethyl or an alkali metal salt thereof or hydroxyethyl, and R
6
represents sulphoethyl or an alkali metal salt thereof, hydroxyethyl or disulpho-substituted phenyl.
In a particularly preferred embodiment, the radicals R
3
, R
4
as well as R
1
and R
2
are identical.
The radical M, which preferably represents hydrogen or an alkali metal, such as sodium, potassium or lithium, does not have to be identical on each sulphonic acid group in the molecule.
It is furthermore preferable to adjust the reaction mixture obtainable by the process according to the invention to a pH of less than 10, preferably less than 8, for the purpose of working up, and to remove the excess C
1
-C
4
-monoalkanol, preferably by distillation.
The invention furthermore relates to compounds of the formula (I) which correspond to the formula (IV)
wherein
M has the abovementioned meaning.
Preferred compounds of the formula (IV) are those in which the SO
3
M groups of the terminal benzene ring are in the 2- and 5-position.
The compounds of the formula (IV) can be prepared by a procedure analogous to that described above.
The invention furthermore relates to mixtures comprising at least two different compounds of the formula (I), these being prepared by a procedure analogous to that described above.
Mixtures which comprise three different compounds of the formula (I) in which R
1
and R

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