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Патент USA US2108712

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Patented Feb. 15, 1938
Ernst Herdieckerhoff, Opladen, near Cologne, and
Eduard Tschunkur, (lologne-Mulheim, Ger
many, assignors to I. G. Farbenindustrie Ak
tiengesellschaft, Frankfort-on-the-Main, Ger
No Drawing. Application October 5, 1934, Se
rial No. 747,090. In Germany October 12,
4 Claims.
(Cl. 260-44)
The present invention relates to a process for
the manufacture of heterocyclic hydroxy com
pounds, more particularly it relates to com
pounds which may' be represented by the proba
ble general formula:
wherein 0: stands for sulfur or oxygen.
In accordance with the present . invention
heterocyclic hydroxy compounds of the above
identi?ed formula are prepared by starting with
a sulfonic acid of the general formula:
saponifying agents, such as dilute phosphoric
acid or dilute aqueous alkalies, such as dilute
aqueous caustic soda lye or dilute aqueous caus
tic potassium lye, say from 1-10% strength, gen
erally require higher temperatures, say from *1
about 50° to about 100° C. It is to be understood
that the statements hereinbefore made with re
gard to the concentration and temperature are in
no Way limitative and that the conditions of
working may be varied in any suitable‘ manner 10
without departing from the spirit of our inven
The sulfonic; acids used as starting compon
ents in our invention are obtainable, for example,
according to the process described in the appli
cation for Letters Patent Serial No. ‘723,611, filed
May 2, 1934 and having the title “Heterocyclic
sulfonic acids and process of making same”, by
reacting upon the corresponding Z-mercapto de
wherein a: means the same as stated above, or a
salt thereof, especially a water soluble salt, such
as an alkali metal salt, and treating the same
rivatives, favorably in an alkaline medium, with "
an oxidizing agent in a quantity corresponding to
at least 3 atoms of active oxygen for each atom
with a saponifying agent. The reaction proceeds
of the 2-mercapto derivative. Further these sul
in such a manner that the sulfonic acid group is
fonic acids are obtainable by reacting upon com
saponi?ed with a splitting off of sulfurous acid.
pounds of the formula:
As saponifying agents suitable for carrying out
the process there come into consideration all the
agents known in the art for performing saponifi
cation; for example, there can be used acid
saponifying agents, such as diluted aqueous min
3 o, eral acids, for example, hydrochloric acid, sul
furic acid, phosphoric acid and the like, further
acid salts, such as bisulfate and the like. Like—
wise the process can be performed with the aid
wherein as means the same as stated above, with a
It is self-understood that in performing our
new process it is not necessary to start with the
isolated sulfonic acids, but the same can be di
of an alkaline saponifying agent, dilute aqueous
caustic soda lye or aqueous caustic potassium lye
being enumerated by way of example.
The conditions of working, i. e. temperature
and concentration of the saponifying agent, de
pend to a high degree on the speci?c heterocyclic
sulfonic acid which is subjected to the reaction
and to the speci?c saponifying agent used. Thus,
for example, when subjecting an oxazole-Z-sul
rectly saponi?ed in the reaction mixtures result "35
ing from their process of manufacture.
The invention is illustrated by the following
fonic acid to our new process, there can be gen
mula :
applied moderate conditions, while in case
4 erally
of thiazole sulfonic acids generally stronger con
examples, without being limited thereto:
Example 1.—50 kgs. of the sodium salt of
benzoxazole-Z-sulfonic acid are dissolved in
300-400 litres of warm water, and the solution
is Weakly acidi?ed with hydrochloric acid.
Z-hydroxybenzoxazole having the following for
ditions, such as the application of an aqueous
mineral acid, say of about 1 to 5% strength, and
higher temperatures, say‘ between about 50 and
aboutv 100° C., are preferable. Quite generally,
when using strong saponifying agents, such as.
dilute aqueous mineral acids, say of from about
. l to about 5% strength, the saponi?cation can
be performed at lower temperatures, in some
cases even at normal temperature, while weaker
of the melting point 140° C. separates in a good
yield with splitting off of sulfurous acid.
Example 2.—-50 kgs. of the sodium salt of s~
naphthoxazole-Z-sulfonic acid are dissolved in
about 300 litres of warm water; on acidifying
the solution with sulfuric acid, sulfurous acid is 55
split off with formation of Z-hydroxy-c-naph
thoxazole of the formula:
5-chloro-2-hydroxybenzothiazole of the formula:
of the melting point 218° C.
‘6-methoxy-2-hydroxybenzothiazole of the for
mula :
of the melting point 206° C. in a good yield.
benzothiazole are dissolved with about 240 kgs.
of aqueous caustic soda lye of 50% strength in
15 about 1000 litres of water at 20-30° C., and to the
solution there are slowly added, while stirring,
340 kgs. of aqueous hydrogen peroxide solution
of 30% strength. Thereby is formed in a rather
quantitative yield the sodium salt of the 2-hy
20 droxy-6-nitrobenzothiazole having in the free
state the following formula:
Example 3.-—212 kgs. of 2-mercapto-6-nitro—
\s /
of the melting point 163-164° C.
2-hydroxy-a-naphthothiazole of the formula:
by splitting oif sulfurous acid from the corre
of the melting point 287-288" C.
2-hydroxy-p-naphthothiazole of the formula:
sponding 2-sulfonic acid which intermediarily
has formed. After redissolving from aqueous
30 caustic soda lye and salting out with common
salt, the sodium salt of 2-hydroxy-6-nitrobenzo
thiazole is obtained in form of yellowish crys
tals; the free compound shows the melting point
252° C.
In an analogous manner there is prepared
the 2-hydroXy-5—nitrobenzothiazole of the melt
ing point 282° 0.
Example 4.—40 kgs. of 2-mercapto-benzothia
of the melting point 235° C.
zole are dissolved with 25 kgs. of aqueous caustic
in accordance with the new process can be used
soda lye of 50% strength in 100 litres of water,
as intermediate products for the manufacture of
and at 20-30° C. there is slowly added a solution
of 80 kgs. of potassium permanganate in about
800 litres of water. After this the reaction mix
ture is heated to 80-90° (3., and the manganese
45 sludge formed is ?ltered off. The ?ltrate con
taining the benzothiazole-Z-sulfonic- acid is ren
dered acid to congo with hydrochloric acid, while
hot, whereupon the bulk of the 2-hydroxybenzo
thiazole separates directly with a strong de
A further quantity of the 2
hydroxybenzothiazole crystallizes on cooling.
The output is about 90% of theory. The product
The Z-hydroxyarylene compounds obtainable
synthetic drugs and other technically valuable 40
We claim:
1. The process of preparing a compound of the
group consisting of 2~hydroxyoxazoles and 2
hydroxythiazoles which comprises splitting o?f 45
sulfurous acid from a compound of the general
50 velopment of S02.
having the following formula:
is very pure and shows the melting point of
60 138° C.
The process can also be performed at other
temperatures between about 50 and about 100° C.
In an analogous manner there are prepared
from the corresponding benzothiazole-2-sulfonic
65 acids or naphthothiazole-Z-sulfonic acids re
4-chloro-2-hydroxybenzothiazole of the formula:
C-eS 03y
\ /
wherein ar stands for an arylene radical of the
benzene or naphthalene series, :0 stands for a
member of the group consisting of sulfur and
oxygen, and 1! stands for a member of the group 55
consisting of hydrogen and a monovalent metallic
radical, by treating with an acid saponifying
2. A process as claimed in claim 1, in which a
dilute aqueous mineral acid is used as saponify 60
ing agent.
3. The process of preparing 2-hydroxyoxazole
which comprises treating oxazole-Z-sulfonic acid
with dilute aqueous hydrochloric acid at normal
4. The process of preparing 2-hyclroxybenzo
thiazole which comprises treating benzothiazole
2-sulfonic acid with dilute aqueous hydrochloric
acid at a temperature between about 50 and
about 100° C.
of the melting point 204-205" C.
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