The Manufacture of Indigo Leuco-products and Colouring-matters, and of Intermediate Compounds relating thereto.
Year: 1898

page_text: The Manufacture of Indigo Leuco-products and Colouring-matters,
and of Intermediate Compounds relating thereto.
I, BENJAMIN WILLCOX, of 47, Lincoln's Inn Fields, in the County of London,
Patent Agent, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by the Badische Anilin & Soda Fabrik, of Ludwig-
shafen-on-Rhine, in the German Empire,) to be as follows:-
This invention relates to the manufacture of colouring matters of the indigo series,
and of leuco products and intermediate compounds relating thereto. According to
this invention piperazine compounds are prepared from glycocoll carboxy acids and
then these new piperazine derivatives are treated with a caustic alkali. In the melt
so obtained, leuco compounds of the indigo colouring matters are contained, and they
can either be separated as such, or be oxidised to the indigo colouring matter itself.
It has long been known that simple phenyl-glycocoll compounds, on heating are
converted into anhydrides, which are regarded chemically as keto-piperazines, but
up to the present no means have been known of preparing corresponding compounds
from glycocoll-carboxylic-acids which are derived from amido-malonic acid. Accord-
ing to the publications hitherto made these bodies when treated to yield anhydrides
give not piperazine but indoxyl derivatives.
My foreign correspondents have found that new piperazine derivatives can be
obtained by heating the esters of the glycocoll carboxylic acids mentioned with an
indifferent solvent, or alone, at a temperature exceeding 200 degrees Centigrade.
The re-action product can be freed from bye products by extracting it by means of
an organic solvent, such as alcohol, or acetone, in which the piperazine derivative is
but slightly soluble.
The new piperazines, obtained according to this invention, are insoluble in dilute
acids and alkalies, very slightly soluble in chloroform and methyl alcohol, but readily
soluble in boiling nitro-benzene, or aniline. The solution of these bodies in concen-
trated sulphuric acid is intensely fluorescent and possesses a characteristic absorption
spectrum.
In the second stage of the process the piperazine derivatives according to the first
stage are melted together with fixed caustic alkali, with, or without, the addition of
lime, and a yellow to red melt is obtained. This contains leuco compounds of indigo
colouring matters, which can be precipitated by means of acids, or converted into the
indigo colouring-matter by dissolving the melt in water, and oxidising by means of
air, or other suitable oxidising agent.
The following examples will serve to illustrate the nature of this invention, but it
is not confined to these examples. The parts are by weight.

page_text: Mix together one part of the tolyl-piperazine-derivative obtained as described in
Example 1, and four parts of caustic potash, and heat the mixture at a temperature of
about 250 to 280 degrees Centigrade, excluding air as far as possible. Maintain the
temperature until the melt has assumed a deep orange-red colour, and it can be
ascertained by testing that the highest yield of colouring-matter is being obtained.
Allow the melt to cool, powder it, and, if it be desired to obtain the product in the
form of leuco compound, add to it six parts of ice-cold dilute sulphuric acid,
(containing about 25 per cent. real acid H,SO). Filter the product which separates
out. If it be desired to obtain the blue indigo colouring-matter itself direct, dissolve
the melt in water and precipitate the colouring matter, for instance, by oxidising
with air.
The foregoing Example 3 illustrates the manner in which the second stage of the
process is effected. Other piperazine derivatives obtained according to the first stage
can be treated in a similar manner.
Dated 1 3
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London,W.C., Agents.

page_text: The Manufacture of Indigo Leuco-products and Colouring-matters,
and of Intermediate Compounds relating thereto.
I, BENJAMIN WILLCOX, of 47, Lincoln's Inn Fields, in the County of London,
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me from abroad by the Badische Anilin & Soda Fabrik, of
Ludwigshafen-on-Rhine, in the German Empire,) and in what manner the same
is to be performed to be particularly described and ascertained in and by the
following statement :-
This invention relates to the manufacture of colouring-matters of the indigo
series, and of leuco products and intermediate compounds relating thereto.
According to this invention piperazine compounds are prepared from glycocoll carboxy
acids and then these new piperazine derivatives are treated with a caustic alkali. In
the melt so obtained, leuco compounds of the indigo colouring-matters are contained,
and they can either be separated as such, or be oxidised to the indigo colouring-
matter itself.
It has long been known that simple phenyl-glycocoll compounds, on heating,
are converted into anhydrides, which are regarded chemically as keto-piperazines,
but up to the present no means have been known of preparing corresponding
compounds from glycocoll-carboxylic-acids which are derived from amido-malonic
acid. According to the publications hitherto made, these bodies, when treated to
yield anhydrides give, not piperazine, but indoxyl, derivatives.
My foreign correspondents have found that new piperazine derivatives can be
obtained by heating the esters of the glycocoll-carboxylic acids which are derived
from amido-malonic acid, with an indifferent solvent, or alone, at a temperature
exceeding 200 degrees Centigrade. The reaction product can be freed from
bye-products by extracting it by means of an organic solvent, such as alcohol, or
acetone, in which the piperazine derivative is but slightly soluble.
The new piperazines obtained according to this invention are insoluble in dilute
acids and alkalies, very slightly soluble in chloroform and methyl alcohol, but readily
soluble in boiling nitro-benzene, or aniline. The solution of these bodies in
concentrated sulphuric acid is intensely fluorescent, and possesses a characteristic
absorption spectrum.
In the second stage of the process the piperazine derivatives according to the first
stage are melted together with fixed caustic alkali, with, or without, the addition of
lime, and a yellow to red melt is obtained. This contains leuco compounds of indigo
colouring-matters, which can be precipitated by means of acids, or converted into the
indigo colouring-matter by dissolving the melt in water, and oxidising by means of
air or other suitable oxidising agent.
The following examples will serve to illustrate the nature of this invention and the
manner in which it can be best carried into practical effect, but the invention is not
limited to these examples. The parts are by weight.

page_text: PRODUCTION OF THE INDIGO LEUCO PRODUCTS AND COLOURING MATTERS FROM THE
PIPERAZINE DERIVATIVE.
Mix together one part of the tolyl-piperazine-derivative obtained as described in
Example 1, and four purts of caustic potash, and heat the mixture to a temperature
of about 250 to 280 degrees Centigrade, excluding air, as far as possible. Maintain
the temperature until the melt has assumed a deep orange-red colour and it can be
ascertained by testing that the highest yield of colouring-matter is being obtained.
Allow the melt to cool, powder it, and, if it be desired to obtain the product in the
form of leuco compound, add to it six parts of ice-cold dilute sulphuric acid (containing
about 25 per cent. real acid H.SO.). Filter the product which separates out. If it be
desired to obtain the blue indigo colouring-matter itself direct, dissolve the melt in
water and precipitate the colouring-matter, for instance, by oxydising with air.
The foregoing Example 3 illustrates the manner in which the second stage of the
process is effected. Other piperazine derivatives obtained according to the first stage
can be treated in a similar manner.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The manufacture of piperazine compounds from phenyl-glycocoll-carboxylic
acids, derived from amido-malonic acid, by heating them to a temperature exceeding
200 degrees Centigrade.
2. The manufacture of piperazine compounds from phenyl-glycocoll-carboxylic
acids, derived from amido-malonic acid by heating them with a solvent to a
herein before
temperature exceeding 200 degrees Centigrade substantially as
described.
3. The manufacture of piperazine compounds from phenyl-glycocoll-carboxylic
acids, derived from amido-malonic acid by heating them to a temperature exceeding
200 degrees Centigrade, powdering the solidified product and extracting by means
of a solvent substantially as herein before described.
4. The manufacture of indigo leuco products by first preparing the piperazine
derivatives in the nanner hereinbefore described, and claimed in the first

page_text: claiming clause, and then melting the said piperazine derivatives together with
a fixed caustic alkali.
5. The manufacture of indigo leuco products by melting together piperazine
derivatives, such as can be obtained as hereinbefore described and claimed in the
first claiming clause, with a fixed caustic alkali.
6. The manufacture of indigo colouring-matter by preparing the indigo leuco
product substantially as hereinbefore described and claimed in the second and third
claiming clauses and then oxydising the said leuco product in aqueous solution.
7. The manufacture of the new piperazine derivatives and of the indigo leuco
products and colouring-matters, substantially as hereinbefore described in the
foregoing examples.
8. As new products the new piperazine derivatives such as can be obtained
substantially as hereinbefore described.
Dated this 20th day of June 1900
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.